Smart junction box based on double RS485 communication, photovoltaic assembly, and photovoltaic system

Abstract

Disclosed in the present invention are a smart junction box based on double RS485 communication, a photovoltaic assembly, and a photovoltaic system. The smart junction box comprises a power unit and a control unit, wherein the power unit is connected to the control unit, and the power unit is used for implementing a state switching operation of a photovoltaic assembly between a string working mode and a bypass mode; and the control unit is internally provided with two RS485 communication electronic elements, and is used for monitoring in real time a working state of a current component and an operation condition of the entire main circuit, and sending a corresponding state switching instruction to the power unit on the basis of monitoring data. Using a double RS485 communication technique in combination with the design of a built-in power unit and control unit, the smart junction box of the present invention realizes the precise monitoring and control of a working state of a photovoltaic component and supports flexible wiring manners; moreover, the stability of communication under different ground potential conditions is ensured by means of a digital isolation electronic element, and thus an efficient and smart photovoltaic string management system having strong adaptability is constructed.

Description

Intelligent junction box based on double RS485 communication, photovoltaic module and photovoltaic system TECHNICAL FIELD

[0001] The present application relates to the technical field of photovoltaic junction boxes, and particularly relates to an intelligent junction box based on double RS485 communication, a photovoltaic module and a photovoltaic system. BACKGROUND

[0002] In order to reduce safety hazards and power generation losses from a single component, several existing solutions have been formed in the industry:

[0003] (1) Shutoff: A single shutoff is placed on the back of the component. In the event of extreme conditions such as fire, DC arc, or string short circuit, all components in the string are bypassed to prevent the formation of local high voltage and safety hazards.

[0004] (2) Optimizer: For components with power loss, a component-side MPPT algorithm topology is used to achieve current matching with other normal components, thereby not affecting the MPPT function of the inverter and improving overall power generation efficiency.

[0005] (3) Micro-inverter: The micro-inverter function is to connect the component individually or in parallel to the DC side of the inverter, avoiding the high voltage formed by the component in series, thereby greatly reducing the power mismatch problem caused by the component in series.

[0006] The above three solutions each have their own functions in photovoltaic power electronics at the component level and are suitable for certain special occasions to solve individual problems, but they all significantly increase the cost of the component, making it difficult to promote and use.

[0007] The industry has produced an intelligent junction box that directly embeds intelligent circuits and devices into the back of the component to replace the conventional junction box with only bypass protection function to achieve component safety and working condition monitoring and optimization function. However, the internal circuit of the conventional photovoltaic component is mainly in series, and to comprehensively monitor and protect the photovoltaic component, an intelligent protection circuit and device need to be set up between every two strings. Early intelligent protection circuits mainly use imported chips for secondary development of peripheral circuits, and three sets of chip circuits and devices are used for each component, but the high price of imported chips leads to high cost of the intelligent junction box, making it impossible to mass-produce and apply this solution.

[0008] For future photovoltaic power station operation and maintenance, state monitoring and safety protection need to be sunk to the component level, which can greatly improve power generation efficiency and greatly improve the reliability and life of the power station, which requires an innovative solution that can support the required functions while considering the cost. SUMMARY

[0009] The application aims to provide a smart junction box based on double RS485 communication, which can realize intelligent monitoring of photovoltaic modules and greatly improve the stability and efficiency of monitoring communication.

[0010] Technical scheme: In order to achieve the above application purpose, the smart junction box based on double RS485 communication comprises a mainboard, wherein a smart module is installed on the mainboard, the smart module comprises a power unit and a control unit, the power unit is connected with the control unit,

[0011] The power unit is used for realizing state switching operation of the photovoltaic module between string operation mode and bypass mode.

[0012] The control unit is internally provided with two-way RS485 communication electronic elements, which are used for monitoring the working state of the current module and the running state of the whole main circuit in real time, and sending corresponding state switching instructions to the power unit according to the monitoring data.

[0013] Further, the mainboard is provided with a power input cable and a power output cable,

[0014] The positive and negative cables of two photovoltaic modules adjacent to each other are connected with the power unit through the power input cable and the power output cable.

[0015] Further, the power input cable and the power output cable are one or more.

[0016] Further, the mainboard is further provided with a power input interface, a power output interface and a communication interface.

[0017] Further, the mainboard is further provided with a first communication cable and a second communication cable, and the first communication cable and the second communication cable are connected with the smart module respectively.

[0018] Further, the control unit is further provided with a digital isolation electronic element.

[0019] Further, one or more bypass diodes are included.

[0020] A smart photovoltaic module, wherein the positive and negative cables of two photovoltaic modules adjacent to each other are connected with the power unit of the smart junction box through the power input cable and the power output cable of the smart junction box.

[0021] Further, each of the photovoltaic modules corresponds to one or more smart junction boxes.

[0022] An intelligent photovoltaic system, comprising a plurality of intelligent junction boxes, a plurality of photovoltaic modules, an inverter and a gateway,

[0023] The positive and negative cables of the photovoltaic modules are connected with the power input interfaces or power input cables of a plurality of the intelligent junction boxes, a plurality of adjacent photovoltaic modules are connected in series through the power output cables of the intelligent junction boxes into a photovoltaic array, and the photovoltaic array is connected with the inverter.

[0024] The first communication cable and the second communication cable of the intelligent junction box are connected in series with a plurality of adjacent photovoltaic modules to the gateway.

[0025] Beneficial effects: The intelligent junction box of the present application utilizes the double RS485 communication technology, combines the design of the built-in power unit and the control unit, realizes the accurate monitoring and control of the working state of the photovoltaic module, supports flexible wiring mode (built-in or externally hung), and ensures the stability of communication under different ground potential conditions through digital isolation electronic elements, thereby constructing an efficient, intelligent and adaptable photovoltaic string management system. BRIEF DESCRIPTION OF DRAWINGS

[0026] Figure 1 is a schematic diagram of the structure of the intelligent junction box of embodiment 1;

[0027] Figure 2 is a schematic diagram of the structure of the intelligent junction box of another embodiment of embodiment 1;

[0028] Figure 3 is a schematic diagram of the structure of the photovoltaic module of embodiment 2;

[0029] Figure 4 is a schematic diagram of the structure of the photovoltaic module of another embodiment of embodiment 2;

[0030] Figure 5 is a schematic diagram of the structure of the photovoltaic system of embodiment 3. DETAILED DESCRIPTION EMBODIMENT

[0031] As shown in Figures 1 and 2, an intelligent junction box based on double RS485 communication, comprising a main board 1, an intelligent module is installed on the main board 1, the intelligent module includes a power unit 2 and a control unit 3, the power unit 2 is used to realize the state switching operation of the photovoltaic module between the string working mode and the bypass mode;

[0032] Two N-channel MOS tubes are provided in the power unit 2, when the circuit is in the string working mode, an N-channel MOS tube is connected in series between the photovoltaic module and the system main loop, the source of the MOS tube is connected to the negative electrode of the photovoltaic module, the drain is connected to the negative end of the system main loop, and a voltage higher than the threshold voltage (V th ) of the MOS tube is applied to the gate, usually V gs = V g - V s >V thwhere V g is the gate voltage, V s is the source voltage (approximately ground potential). This makes the channel inside the MOS tube fully open, and the drain-source resistance close to the minimum value, allowing the current generated by the photovoltaic module to flow almost unimpeded through the MOS tube to the system load, at this time the MOS tube acts as an "open circuit" device, that is, in a fully on state, so that a low impedance path is formed between the photovoltaic module and the system main circuit.

[0033] When the circuit is in bypass mode, an additional N-channel MOS tube is connected in parallel between the photovoltaic module and the system main circuit, the source of which is still connected to the negative pole of the photovoltaic module, but the drain is connected to the bypass diode. Normally, this bypass MOS tube should be kept in the off state. A fault detection circuit is set up to monitor parameters such as voltage, current or temperature of the photovoltaic module. Once a fault condition is detected, the fault detection circuit should quickly trigger the control logic to change the gate voltage of the bypass MOS tube, making it V gs lower than the threshold voltage (V gs <V th ), so that the MOS tube changes from off to on. At this time, the current of the photovoltaic module no longer flows through the main circuit, but through the bypass MOS tube that has been turned on and flows into the bypass diode, achieving fault isolation.

[0034] The control unit 3 is connected to the power unit 2 and has two 485 interface chips inside, which are used to monitor the working state of the current module and the running state of the entire main circuit in real time. Based on these monitoring data, the control unit 3 can determine when the working state of the module needs to be adjusted, and accordingly issue corresponding instructions to the power unit 2, such as switching the module to bypass mode to deal with faults or abnormal conditions, or restoring to normal working mode to optimize system performance.

[0035] The control unit 3 uses a microcontroller (MCU) to monitor the working state of the current module and the operation of the entire main circuit in real time. The MCU runs embedded software to filter and calculate the collected voltage, current, and temperature data, such as power, efficiency, maximum power point tracking (MPPT), and other parameters, to evaluate the module's working state. The software implements a fault identification algorithm to determine whether the module has short-circuit, open-circuit, hot spot, PID effect, or other faults through threshold comparison, trend analysis, and feature recognition. Based on the monitoring results, the MCU controls the gate drive circuit of the MOS tube in the power unit through PWM (pulse width modulation) or digital output signals to perform state switching operations. When a fault is detected or maintenance is needed, the MOS tube is sent into bypass mode. After returning to normal, the MOS tube is turned on again to restore the module to string operation mode. The MCU exchanges data with the upper monitoring system or the control unit of the adjacent module through RS-485, CAN, Wi-Fi, Bluetooth, and other communication interfaces, reports the module state, receives control instructions, and realizes information link and remote monitoring between strings.

[0036] The power unit switches the working mode of the photovoltaic module by switching the on and off states of the MOS tube, and the control unit integrates multiple sensors through the MCU to perform data collection and processing, fault diagnosis, state switching control, and communication functions to monitor the module state and the operation of the main circuit in real time, ensuring the stable and efficient operation of the photovoltaic system.

[0037] Considering that the photovoltaic module may cause potential differences between modules when connected in series, to ensure the reliability of communication in different potential environments, digital isolation electronic components are added to the communication interface inside the control unit 3. These electronic components can effectively isolate signals between different potentials, eliminate potential ground potential difference interference, and ensure the stability and smoothness of communication lines between different modules.

[0038] The main board 1 is provided with a plurality of power input cables 4 and a plurality of power output cables 5. The positive and negative electrode cables of two adjacent photovoltaic modules are connected to the power unit 2 through the power input cable 4 and the power output cable 5 respectively. The photovoltaic module itself has a pair of main power cables, one of which carries positive electrode current and the other of which carries negative electrode current. The two cables are directly connected to the main board 1 of the intelligent module, and further electrically connected to the corresponding power input port of the power unit 2. In this way, the electrical energy generated by the photovoltaic module can enter the subsequent power transmission path through the power unit 2. In order to construct a continuous circuit of the entire photovoltaic module string, each module needs to not only receive the electrical energy transmitted from the previous module, but also transmit the electrical energy generated by itself to the next module. Therefore, the power output cable 5 of the power unit 2 is precisely connected to the positive and negative electrode cables of the two adjacent photovoltaic modules of the current module. This series connection ensures the orderly flow of electrical energy of all modules in the string, forming a complete current loop, thereby realizing efficient power generation.

[0039] The main board 1 is also provided with a first communication cable 6 and a second communication cable 7, and the first communication cable 6 and the second communication cable 7 are respectively connected to two 485 interface chips. The two communication cables are connected to the two 485 interface chips of the control unit 3 through the main board 1, and are respectively connected to the communication interfaces of the front and rear adjacent photovoltaic modules, responsible for transmitting the data in the control unit 3 to the adjacent modules in the string, thereby ensuring the formation of information link in the string or between the strings. This hand-in-hand communication network layout ensures smooth communication between all modules in the entire string, so that control commands, state information and other data can be quickly transmitted within the string, which is conducive to the realization of functions such as overall monitoring, fault diagnosis and remote control of the system.

[0040] According to the different circuit structures of the photovoltaic module, the above-mentioned intelligent junction box can be directly arranged on the back of the photovoltaic module and integrated with the module itself, or can be externally mounted with the photovoltaic module as an independent device, at which time the form and structure of the power input cable 4 will be different.

[0041] As another embodiment of the present embodiment, the main board 1 of the intelligent junction box is also provided with a power input interface 8, a power output interface 9 and a communication interface 10, and the intelligent junction box can be directly installed on the back of the photovoltaic module and integrated with the module. At this time, the cables led out of the module can be directly welded on the power input interface 8, realizing compact and integrated connection.

[0042] As another embodiment of the present embodiment, the intelligent junction box can also be installed as an independent device outside the photovoltaic module. In this configuration, the power input cable 4 of the main board 1 extends outside the box body, and the cable is connected to the positive and negative electrode cables of the photovoltaic module, realizing the transmission of electrical energy between the junction box and the module.

[0043] The embodiment adopts a double RS485 communication interconnection mode, which can better sort out the communication objects of the components, avoid data loss and communication error codes caused by process problems in one-to-many communication, and conveniently establish a chain type component communication structure, so that the data exchange between the background and the single component can be realized in a hierarchical manner. In addition, the double RS485 communication mode ensures the consistency of the length of the cable, thereby avoiding the difference in communication signal strength and the formation of time delay between components. The data processing in the control unit 3 is also optimized and the efficiency is improved.

[0044] Because the signal is reorganized and enhanced at each node, the reliability of the signal and the entire communication link is ensured. In addition, compared with PLC communication, 485 communication has a wider bandwidth, which can ensure that more components are connected in a single link. Moreover, the cost of 485 communication is much lower than that of PLC communication, and the power consumption is lower. Therefore, the double RS485 communication mode can greatly reduce the cost of intelligent transformation of photovoltaic power stations. Embodiment

[0045] As shown in FIG. 3, a smart photovoltaic module is composed of six battery strings, three of which are connected in parallel, and the positive and negative ends of the first three battery strings are connected to the positive and negative ends of the last three battery strings. At this time, the photovoltaic module adopts a parallel circuit design, and there are two cables in total, one positive and one negative. The two cables are on the same line and have a short distance apart, with a distance of 5-20 mm, and can be arranged on the same mainboard. The positive and negative cables on the photovoltaic module are generally tinned copper flat strips, and the two positive and negative cables can be directly welded to the power input cable interface on the mainboard of the intelligent junction box, so that the intelligent junction box and the photovoltaic module form an integrated whole. At this time, the intelligent junction box shown in FIG. 2 can be used. This direct welding method enhances the mechanical stability and electrical connection reliability between the module and the junction box, simplifies the installation process, reduces the additional wiring steps, and helps to improve the integration and work efficiency of the overall system. This photovoltaic module adopts a parallel circuit design, so that the positive and negative cables can be compactly arranged on the same mainboard, further improving the space utilization and simplifying the wiring structure, which is conducive to the integration of the module and the junction box.

[0046] As another embodiment of the present embodiment, as shown in FIG. 4, a conventional module generally adopts multiple battery strings in series. The present embodiment adopts eight battery strings, which are connected in parallel in pairs and then connected in series, forming two positive and negative cables with a long distance. At this time, the intelligent junction box shown in FIG. 1 can be used. Embodiment

[0047] As shown in FIG. 5, a smart photovoltaic system includes four intelligent junction boxes, multiple photovoltaic modules, an inverter, and a gateway.

[0048] The positive and negative power cables of the photovoltaic module are connected with the power input interfaces or power input cables of the plurality of intelligent junction boxes, a plurality of adjacent photovoltaic modules are connected in series into a photovoltaic array through the power output cables of the intelligent junction boxes, and the photovoltaic array is connected with an inverter.

[0049] The first communication cable and the second communication cable of the intelligent junction box are connected in series with a plurality of adjacent photovoltaic modules to a gateway. The power input cable of the intelligent junction box is connected with the positive and negative level cables of the module itself, the module power circuit is connected to the intelligent junction box, adjacent modules are connected in series through the power output cable to form a direct current side loop, adjacent modules are connected through the communication cable to form a data communication loop, and finally, the working state data of the power station are transmitted to the cloud for processing through the gateway, so that the working state of the power station and the module itself can be monitored.

[0050] When a certain module in the photovoltaic array is shaded, the working current of the module will decrease significantly, which will cause the output power of the entire array to be affected by the same proportion.

[0051] On one hand, the intelligent module inside the junction box will monitor the change of the current, and continuously compare it with historical data and set data. If the set safety value is exceeded, it means that the module has a continuous power generation impact on the entire circuit. If the module is bypassed, the power generation loss of the entire photovoltaic array can be reduced. The junction box issues a bypass instruction to bypass the module from the entire series array, thereby reducing the power generation loss.

[0052] When a certain module in the photovoltaic array is impacted by external force, although there is no apparent problem on the surface, the internal battery pieces have many hidden cracks. Over time, the continuous accumulation of heat causes changes in current or voltage, and the overall module decays beyond the normal value. At this time, the power generation of the entire array will also be affected. Over time, it may even cause a fire risk. For such a module, the intelligent junction box compares historical data and initial data with the working state data of other modules in the array and finds a continuous decay trend. In order to reduce the safety risk, the intelligent junction box can also issue a bypass instruction to bypass the module from the array and stop working, so that the risk no longer worsens, thereby realizing the function of active safety.

[0053] For the identified risks, the intelligent junction box can provide accurate location information and risk warning information through the communication cable and the gateway, through the cloud backend, to remind the operation and maintenance personnel to take accurate measures to handle.

[0054] The intelligent junction box in the application has the functions of monitoring, communication and optimization, has a simple structure, is easy to operate and construct, has reliable communication and stable operation, and has practical effects in ensuring the safety of the photovoltaic power station and the income of the power station.

[0055] The above merely describes the preferred embodiments of the present application, and it should be pointed out that those skilled in the art can make several improvements and refinements without departing from the principles of the present application, and these improvements and refinements should also be considered as falling within the protection scope of the present application.

Claims

1. An intelligent junction box based on dual RS485 communication, characterized in that: It includes a mainboard, on which an intelligent module is installed. The intelligent module includes a power unit and a control unit. The power unit is connected to the control unit. The power unit is used to implement the state switching operation of the photovoltaic module between the string operation mode and the bypass mode; The control unit is internally provided with two RS485 communication electronic components for real-time monitoring of the working status of the current components and the operating status of the entire main circuit, and for issuing corresponding state switching instructions to the power unit according to the monitoring data.

2. The intelligent junction box based on dual RS485 communication according to claim 1, characterized in that, The mainboard is provided with a power input cable and a power output cable. The positive and negative cables of two upper and lower adjacent photovoltaic modules are connected to the power unit through the power input cable and the power output cable respectively.

3. The intelligent junction box based on dual RS485 communication according to claim 2, characterized in that, There are one or more power input cables and one or more power output cables.

4. The intelligent junction box based on dual RS485 communication according to claim 2, characterized in that, The mainboard is also provided with a power input interface, a power output interface and a communication interface.

5. The intelligent junction box based on dual RS485 communication according to claim 2, characterized in that, The mainboard is further provided with a first communication cable and a second communication cable, and the first communication cable and the second communication cable are respectively connected to the smart module.

6. The intelligent junction box based on dual RS485 communication according to claim 1, characterized in that, The control unit is also provided with digital isolation electronics.

7. The intelligent junction box based on dual RS485 communication according to claim 1, characterized in that, Include one or more bypass diodes.

8. A smart photovoltaic module, characterized in that: The positive and negative cables of two upper and lower adjacent photovoltaic modules are connected to the power unit of the smart junction box through the power input cable and the power output cable of the smart junction box respectively.

9. The smart photovoltaic assembly according to claim 8, wherein: Each of the photovoltaic components corresponds to one or more intelligent junction boxes.

10. An intelligent photovoltaic system, characterized in that: Including multiple smart junction boxes, multiple photovoltaic panels, inverters and gateways, The positive and negative cables of the photovoltaic modules are connected to the power input interfaces or power input cables of the multiple smart junction boxes, and multiple adjacent photovoltaic modules are connected in series through the power output cables of the smart junction boxes to form a photovoltaic array, and the photovoltaic array is connected to the inverter; The first communication cable and the second communication cable of the smart junction box are connected in series with a plurality of adjacent photovoltaic assemblies to the gateway.

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