Anti-reflux device suitable for miniature grid-connected inverter system

Abstract

The invention relates to an anti-countercurrent device suitable for a miniature grid-connected inverter system, which is characterized in that an anti-countercurrent electric meter and at least one miniature grid-connected inverter form a local area network through a local router to form a system, and the anti-countercurrent electric meter accurately acquires power grid parameters through a power grid voltage sampling terminal and a current measurement signal input terminal of the anti-countercurrent electric meter; and the real-time grid-connected power of each micro grid-connected inverter is inquired regularly as a control center, a power adjustment instruction is calculated and broadcasted, and finally all the micro grid-connected inverters are driven to adjust output synchronously. An anti-countercurrent electric meter is used as a unified control core, and a unified power adjustment instruction is calculated based on real-time countercurrent power and total generated power, so that all micro inverters can adjust power synchronously and proportionally, accurate cooperative control of multiple micro inverters is realized, and power oscillation is avoided; the whole control closed loop operates in a high-speed local area network, is quick in response, meets the grid-connected standard requirement for eliminating countercurrent, and effectively guarantees the safe operation of a power grid.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of photovoltaic grid-connected inverters, in particular to a backflow prevention device suitable for a micro grid-connected inverter system. BACKGROUND

[0002] With large-scale application of new energy such as wind energy and solar energy, power grid consumption has become a problem. New energy power generation has intermittency and instability, and if the proportion is too large, it will seriously affect the safe operation of the power grid. In response to this, many countries or regions have introduced policies requiring solar energy to be self-generated and self-used, and the remaining electricity cannot be connected to the grid. According to domestic standards, once backflow occurs, the backflow power needs to be reduced within 2 seconds. There are already some backflow devices, but there are problems such as inability to accurately control the power of multiple micro-inverses, a lot of energy loss in backflow control, and some backflow devices requiring at least one micro-inverter master and one micro-inverter slave, which limits the application. SUMMARY

[0003] In view of the above problems, the present application provides a backflow prevention device suitable for a micro grid-connected inverter system.

[0004] To achieve the above-mentioned purpose, the present application provides a backflow prevention device suitable for a micro grid-connected inverter system, which comprises a backflow prevention ammeter and at least one micro grid-connected inverter. The backflow prevention ammeter has a first Wi-Fi communication module, a power grid voltage sampling terminal and a current measurement signal input terminal. The first Wi-Fi communication module is used to access a local router and form a local area network. The power grid voltage sampling terminal is used to connect a single-phase power grid to detect power grid voltage parameters. The current measurement signal input terminal is used to connect a current transformer to obtain a signal reflecting the size of power grid inflow / outflow current, which is referred to as current signal. The backflow prevention ammeter is configured to calculate real-time backflow power according to power grid voltage parameters and current signal. Each micro grid-connected inverter has a second Wi-Fi communication module, which is used to access a local router and be in the same local area network as the backflow prevention ammeter. The backflow prevention ammeter periodically queries and obtains real-time grid-connected power of the micro grid-connected inverter through the local area network. The required power adjustment instruction is calculated according to the sum of the real-time backflow power and the real-time grid-connected power of all micro grid-connected inverters. The power adjustment instruction is broadcasted and sent through the local area network. The micro grid-connected inverter receives the power adjustment instruction and adjusts its output power according to the power adjustment instruction, so that the real-time backflow power tends to zero.

[0005] In some embodiments, the backflow prevention ammeter periodically queries and obtains real-time grid-connected power of the micro grid-connected inverter through the local area network, comprising: The main control MCU of the reverse current protection ammeter drives the first Wi-Fi communication module through an SPI or UART interface; The first Wi-Fi communication module constructs and sends a state query request data frame based on a UDP broadcast protocol, the destination address of the state query request data frame is a local area network broadcast address, and the state query request data frame has an instruction code; The main control chip of the micro grid-connected inverter captures and analyzes the state query request data frame through a Wi-Fi firmware stack; After confirming the instruction code, the current and voltage sensor data on the inverter output bridge arm are read through an ADC sampling channel, and the real-time grid-connected power of the micro grid-connected inverter is calculated; Alternatively, the micro grid-connected inverter calculates and updates the real-time grid-connected power according to the ADC sampling value every power frequency cycle; The second Wi-Fi communication module constructs a TCP response data packet containing the device ID and real-time grid-connected power data of the micro grid-connected inverter, and sends the TCP response data packet to the IP address of the first Wi-Fi communication module; The first Wi-Fi communication module receives the TCP response data packet and transmits it to the main control MCU through a serial interface; The main control MCU analyzes the data packet and updates the power value of the corresponding micro grid-connected inverter in its internal register according to the device ID in the data packet.

[0006] In some embodiments, the required power adjustment instruction is calculated according to the sum of the real-time reverse current power and the real-time grid-connected power of the micro grid-connected inverter, including: The reverse current protection ammeter reads the real-time reverse current power value and the total grid-connected power value after the real-time grid-connected power of the micro grid-connected inverter is summed up; Determine the sign of the real-time reverse current power value; If the real-time reverse current power value is positive, indicating that the power grid is delivering power to the user, an instruction to increase the output power or maintain the current state is generated; If the real-time reverse current power value is negative, indicating that there is reverse current power, the absolute value of the reverse current power is calculated; The absolute value of the reverse current power is used as the total amount of power adjustment required; According to the ratio of the total amount of power adjustment to the total grid-connected power value, a power down percentage instruction is calculated.

[0007] In some embodiments, the micro grid-connected inverter receives the power adjustment instruction and adjusts its output power according to the power adjustment instruction to make the real-time reverse current power approach zero, including: The second Wi-Fi communication module listens to and receives broadcast data packets from the reverse current protection ammeter; Analyze the data packet, extract the power adjustment instruction, and execute the corresponding operation according to the type of the power adjustment instruction, including: If it is a power down percentage instruction, the output power value to be reduced is calculated according to the product of the power down percentage and the current output power; If it is a power up instruction, the output power reference value is gradually increased according to the preset power ramping rate, and the output power reference value is converted into the actual AC output power; The micro-grid-connected inverter continuously updates the power adjustment instruction until a new instruction is received or the real-time reverse power approaches zero.

[0008] In some embodiments, a local router is further included, and the first Wi-Fi communication module and the second Wi-Fi communication module are both connected to the local router to form a local area network.

[0009] In some embodiments, the grid voltage sampling terminal is used to connect to a single-phase power grid to detect grid voltage parameters, including: The grid voltage sampling terminal is directly connected to the live wire and the neutral wire of the single-phase power grid through a high-resistance voltage dividing resistor network; The output end of the voltage dividing resistor network is connected to a voltage follower circuit composed of an operational amplifier, for impedance matching and signal isolation; The output of the voltage follower is connected to the input channel of an analog-to-digital converter; The analog-to-digital converter converts the analog voltage signal into a digital quantity and transmits it to the reverse flow prevention ammeter; The reverse flow prevention ammeter software calibrates the digital quantity and calculates the effective value, frequency, and phase angle of the grid voltage, which is the grid voltage parameter.

[0010] In some embodiments, the current measurement signal input terminal is used to connect to a current transformer to obtain a signal reflecting the size of the grid inflow / outflow current, denoted as the current signal, including: The current measurement signal input terminal is connected to the secondary side output terminal of the external current transformer, and the primary side of the external current transformer is connected in series to the live wire of the user's power grid total inlet; A precision sampling resistor is included in the input loop of the current measurement signal input terminal, for converting the current signal output by the current transformer into a voltage signal; The voltage signal is amplified and level-shifted by a differential amplification circuit composed of an operational amplifier, and is transformed to the input voltage range required by the analog-to-digital converter; The analog-to-digital converter converts the amplified analog voltage signal into a digital quantity and transmits it to the reverse flow prevention ammeter; The reverse flow prevention ammeter software calibrates the digital quantity and calculates the effective value of the inflow or outflow current and the power direction into or out of the grid, denoted as the current signal, in combination with the phase angle of the grid voltage parameter.

[0011] In some embodiments, the anti-inrush power meter is configured to calculate real-time inrush power according to the grid voltage parameter and the current signal, including: The anti-inrush power meter multiplies the sampled grid voltage instantaneous value and the current instantaneous value to obtain an instantaneous power value; And, integrates the instantaneous power value in one grid fundamental cycle and takes the average value to obtain the active power value of the current cycle; According to the phase relationship between the current signal and the grid voltage parameter, the power flow direction is determined, including: When the current phase lags behind the voltage phase, it is determined that the active power is in the positive direction, that is, the grid supplies power to the user; When the current phase leads the voltage phase, it is determined that the active power is in the reverse direction, that is, the user supplies power to the grid, which is recorded as inrush power; Combine the active power value and the power direction information to generate a signed real-time inrush power value, a positive sign indicates that the grid supplies power to the user, and a negative sign indicates that there is inrush power.

[0012] In some embodiments, the anti-inrush power meter and the micro-grid-connected inverter communicate through UDP protocol or TCP protocol.

[0013] In some embodiments, the anti-inrush power meter periodically performs query, calculation and broadcast sending operation cycle is 0.2-2 seconds.

[0014] Unlike prior art, in the above technical solution, the system composed of the anti-inrush power meter and at least one micro-grid-connected inverter through the local router to form a local area network, the anti-inrush power meter accurately obtains the grid parameters through its grid voltage sampling terminal and current measurement signal input terminal, and serves as the control center to periodically query the real-time grid-connected power of each micro-grid-connected inverter, calculate and broadcast power adjustment instructions, and finally drive all micro-grid-connected inverters to adjust output synchronously. Through the anti-inrush power meter as the unified control core, based on real-time inrush power and total generated power, a unified power adjustment instruction is calculated, so that all micro-invers can be adjusted in proportion, realizing precise cooperative control of multiple micro-invers, avoiding power oscillation; Using smooth proportional down-regulation instead of complete shutdown maximizes the retention of self-generated and self-used power, significantly reducing energy loss; Breaking the master-slave architecture limitation, all micro-invers are equal, users can flexibly expand according to demand, solving the application limitation problem; The entire control closed loop operates in high-speed local area network, responds quickly, meets the grid-connected standard requirement of eliminating inrush, and effectively guarantees the safe operation of the grid.

[0015] The above summary related to the invention is only a summary of the technical solutions of the present application. In order to enable those skilled in the art to more clearly understand the technical solutions of the present application, and then implement the content recorded in the specification and drawings, and in order to enable the above and other purposes, characteristics and advantages of the present application to be more easily understood, the following will be described in combination with the specific embodiments of the present application and the drawings. BRIEF DESCRIPTION OF DRAWINGS

[0016] The accompanying drawings are used to show the principles, implementation manners, applications, characteristics and effects of the specific embodiments and other related contents of the present application, and cannot be considered as limiting the present application.

[0017] In the drawings: FIG. 1 The first processing flow chart of the anti-reflux device described in the specific embodiments; FIG. 2 The second processing flow chart of the anti-reflux device described in the specific embodiments. DETAILED DESCRIPTION

[0018] In order to more clearly explain the possible application scenarios, technical principles, specific schemes that can be implemented, and the purposes and effects that can be achieved of the present application, the following will be described in combination with the specific embodiments listed and the drawings. The embodiments recorded in the present text are only used to more clearly explain the technical solutions of the present application, and therefore only serve as examples, and cannot be used to limit the protection scope of the present application.

[0019] In the present text, the term "embodiment" means that the specific features, structures or characteristics described in combination with the embodiments can be included in at least one embodiment of the present application. The term "embodiment" appearing at various positions in the specification does not necessarily refer to the same embodiment, and does not particularly limit the independence or association between other embodiments. In principle, in the present application, as long as there is no technical contradiction or conflict, the technical features mentioned in each embodiment can be combined in any manner to form a corresponding implementable technical solution.

[0020] Unless otherwise defined, the meanings of the technical terms used in the present text are the same as those generally understood by those skilled in the art to which the present application belongs; the use of related terms in the present text is only for the purpose of describing specific embodiments, and is not intended to limit the present application.

[0021] In the description of the present application, the phrase "and / or" is a description of the logical relationship between the objects, which means that there can be three relationships, for example, A and / or B, which means that there are three cases: A exists, B exists, and A and B exist at the same time. In addition, the character " / " in the present text generally represents that the associated objects before and after are a "or" logical relationship.

[0022] In the present application, the terms such as "first" and "second" are merely used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual number, primary or secondary, or order relationship between the entities or operations.

[0023] In the present application, the "include", "contain", "have" or other similar open expressions used in the statements are intended to cover the non-exclusive inclusion, and these expressions do not exclude the presence of additional elements in the process, method or product including the described elements, so that the process, method or product including a series of elements can not only include those limited elements, but also include other elements not explicitly listed, or also include the elements inherent in such process, method or product.

[0024] As the same understanding in the "Guidelines for Examination", in the present application, the expressions such as "greater than", "less than", "exceed" are understood as not including the number; the expressions such as "above", "below", "within" are understood as including the number. In addition, in the description of the embodiments of the present application, the meaning of "multiple" is more than two (including two), and similar expressions related to "multiple" are also understood in this way, for example, "multiple groups", "multiple times" and the like, unless otherwise explicitly limited.

[0025] In the description of the embodiments of the present application, the spatial-related expressions used, such as "center", "longitudinal", "transverse", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "vertical", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential", and the like, indicate the orientation or positional relationship based on the orientation or positional relationship shown in the specific embodiments or the drawings, and are only for the convenience of describing the specific embodiments of the present application or for the reader to understand, and do not indicate or imply that the indicated device or component must have a specific position, a specific orientation, or be constructed or operated in a specific orientation, and therefore cannot be understood as a limitation of the embodiments of the present application.

[0026] The processor described in the embodiments of the present application can be implemented by hardware, firmware, software or a combination thereof, and can use at least one of circuit, single or multiple application specific integrated circuits (ASIC), digital signal processors (DSP), digital signal processing devices (DSPD), programmable logic devices (PLD), field programmable gate arrays (FPGA), central processing units (CPU), controllers, microcontrollers, microprocessors, and other physical, biological or chemical structures that can realize the same or equivalent functions as the above-mentioned processors, such as biological neurons, quantum computing units, DNA computing units, etc., so that the processor can execute part or all of the steps or any combination of the steps mentioned in the computer programs or methods of various embodiments of the present application.

[0027] The computer program involved in the embodiments can be stored in a computer device readable storage medium, including but not limited to magnetic disk, magnetic tape, magnetic card, floppy disk, flash memory, optical disc, optical card, read-only memory (ROM), random access memory (RAM), erasable programmable ROM (EPROM) and electrically erasable programmable ROM (EEPROM) and the like, and also includes other biological, physical or chemical structures that can realize the same or equivalent functions as the above-mentioned storage media, such as DNA, RNA, protein and the like units with information storage capability. In specific embodiments, the storage medium can be one of the above-mentioned medium types, or a combination of the above-mentioned medium types. In different embodiments, the computer program involved in the embodiments can be centrally stored in a single medium, or distributedly stored in multiple media. The storage medium containing the computer device readable storage medium can be a non-volatile memory or a random access memory. These computer device readable storage media can be built-in in the device, or connected with the device as an external device or part of the external device. In some embodiments, the storage medium with the computer device readable storage medium is deployed locally; in other embodiments, the storage medium can also be deployed remotely from the processor, such as network-attached storage accessed via RF circuit or external port and communication network, wherein the communication network can be the Internet, one or more intranets, local area network (LAN), wide area network (WAN), storage area network (SAN) and the like, or appropriate combination thereof, as long as the access of the computer device to the storage medium can be realized. In addition, the computer program involved in the embodiments can be stored in plaintext / encrypted form, or can be designed as training data, and integrated and reorganized by model training to be implicitly saved in the parameter state of the deep neural network or other machine learning model.

[0028] Please refer to FIG. 1 With FIG. 2 The embodiment provides a backflow prevention device suitable for a micro grid-connected inverter system, which comprises a backflow prevention ammeter and at least one micro grid-connected inverter. The backflow prevention ammeter has a first Wi-Fi communication module, a power grid voltage sampling terminal and a current measurement signal input terminal. The first Wi-Fi communication module is used for accessing a local router and establishing a local area network. The power grid voltage sampling terminal is used for connecting a single-phase power grid to detect power grid voltage parameters. The current measurement signal input terminal is used for connecting a current transformer to obtain a signal reflecting the size of power grid inflow / outflow current, which is referred to as a current signal. The backflow prevention ammeter is configured to calculate real-time backflow power according to the power grid voltage parameters and the current signal. Each micro grid-connected inverter has a second Wi-Fi communication module, which is used for accessing the local router and being in the same local area network as the backflow prevention ammeter. The anti-reverse current meter periodically inquires and obtains real-time grid-connected power of the micro grid-connected inverters through the local area network; the required power adjustment instruction is calculated according to the sum of the real-time reverse current power and the real-time grid-connected power of the micro grid-connected inverters; the power adjustment instruction is broadcasted through the local area network; the micro grid-connected inverters receive the power adjustment instruction and adjust the output power according to the power adjustment instruction, so that the real-time reverse current power approaches zero.

[0029] In the embodiment, the anti-reverse current meter is equipped with a first Wi-Fi communication module, so that it can access the user's local router and form an independent local area network, providing a high-speed and low-latency communication channel for all devices. In addition, the anti-reverse current meter is also provided with two key physical interfaces: a grid voltage sampling terminal and a current measurement signal input terminal. The grid voltage sampling terminal is used to directly connect to the live wire and neutral wire of the single-phase power grid to continuously detect key grid voltage parameters (including voltage, frequency and phase). The current measurement signal input terminal is used to connect an external current transformer, which is clamped at the user's total power grid inlet to obtain current signals reflecting the size and direction of the grid inflow / outflow current. The internal main control unit of the anti-reverse current meter is configured to accurately calculate the real-time reverse current power by calculating the instantaneous power and integrating the average according to the synchronously collected grid voltage parameters and current signals. The power value of the real-time reverse current power is a signed quantity, and the sign clearly indicates the direction of power flow.

[0030] Each micro grid-connected inverter serves as an independent intelligent node. The second Wi-Fi communication module built in the micro grid-connected inverter enables it to also access the above-mentioned local router and be in the same local area network as the anti-reverse current meter, thereby forming a peer-to-peer network.

[0031] In use, the anti-reverse current meter periodically inquires and obtains real-time grid-connected power of all micro grid-connected inverters through the local area network. Specifically, the anti-reverse current meter sends a query request, each micro grid-connected inverter responds and reports its current output power value, and the anti-reverse current meter aggregates these data to obtain the total power generation. The core processor of the anti-reverse current meter intelligently calculates according to the sum of the real-time reverse current power and the real-time grid-connected power of the micro grid-connected inverters. Specifically, it includes judging the direction (positive or negative) of the reverse current power. If there is reverse current (negative power), the required power adjustment instruction (such as the following percentage) is calculated based on the ratio of the absolute value of the reverse current power to the total power generation. If there is no unexpected reverse current, an instruction to increase power may be generated. After the calculation is completed, the anti-reverse current meter broadcasts the power adjustment instruction to all micro grid-connected inverters through the local area network. Each micro grid-connected inverter synchronously receives the power adjustment instruction and adjusts its output power according to the power adjustment instruction. The internal controller of each micro grid-connected inverter precisely controls the power converter by changing the PWM modulation strategy, and finally collectively acts to make the real-time reverse current power approach zero.

[0032] The embodiment realizes precise, synchronous and collaborative control of the power of multiple micro grid-connected inverters by taking the anti-backflow ammeter as a unified control core and based on a high-speed local area network communication architecture. The anti-backflow ammeter obtains high-precision real-time grid data through grid voltage sampling terminals and current measurement signal input terminals, and calculates real-time backflow power. Unified power adjustment instructions are calculated and issued through broadcasting, ensuring that all micro inverters can adjust power without differential speed according to the same proportion, completely avoiding power oscillation caused by asynchronous control, and greatly improving the accuracy and reliability of control. Smooth proportional adjustment is adopted instead of simple start-stop control, and the power of the micro grid-connected inverter is only reduced to the level of eliminating backflow when necessary, thereby maximizing the amount of self-generated and self-used new energy power and significantly reducing the energy loss caused by the anti-backflow function. At the same time, the traditional master-slave hardware binding architecture is broken, and all micro grid-connected inverters have equal status on the network. Users can flexibly add or delete micro inverters according to actual needs, i.e. plug and play, greatly simplifying the installation and expansion process and significantly enhancing application flexibility. The entire control closed loop operates in a low-delay local area network, and the response from detection, calculation to instruction execution is extremely fast, which can continuously meet the requirements of strict grid connection standards and effectively ensure the safe and stable operation of the grid. When there is no backflow, the micro grid-connected inverter can be instructed to quickly increase power to maximize power generation efficiency, and power adjustment is based on current power and percentage, effectively avoiding power oscillation during adjustment and further optimizing system performance.

[0033] In some embodiments, the anti-backflow ammeter periodically queries and obtains real-time grid-connected power of the micro grid-connected inverter through the local area network, including: The main control MCU of the anti-backflow ammeter drives the first Wi-Fi communication module through an SPI or UART interface; The first Wi-Fi communication module constructs and sends a state query request data frame based on a UDP broadcast protocol, the destination address of the state query request data frame is a local area network broadcast address, and the state query request data frame has an instruction code; The main control chip of the micro grid-connected inverter captures and analyzes the state query request data frame through a Wi-Fi firmware stack; After confirming the instruction code, the current and voltage sensor data on the inverter output bridge arm are read through an ADC sampling channel, and the real-time grid-connected power of the micro grid-connected inverter is calculated; Alternatively, the micro grid-connected inverter calculates and updates its real-time grid-connected power according to the ADC sampling value every power frequency cycle; The second Wi-Fi communication module constructs a TCP response data packet containing its device ID and real-time grid-connected power data, and sends it to the IP address of the first Wi-Fi communication module; The first Wi-Fi communication module receives the TCP response data packet and transmits it to the main control MCU through a serial interface; The main control MCU parses the data packet and updates the power value of the corresponding micro grid-connected inverter in its internal register according to the device ID therein.

[0034] In this embodiment, the main control MCU of the reverse flow prevention ammeter drives the first Wi-Fi communication module through its SPI interface or UART interface to initiate a communication process; the first Wi-Fi communication module constructs and sends a state query request data frame based on the UDP broadcast protocol, wherein the destination address of the state query request data frame is set as the local area network broadcast address, and the payload of the state query request data frame contains a specific instruction code for identifying this as a power query request; The main control chip of the micro grid-connected inverter continuously listens to and captures the state query request data frame through its built-in Wi-Fi firmware stack, and parses the data frame; after confirming the matching of the instruction code, the main control chip reads the sampling data of the current sensor and voltage sensor on its inverter output bridge arm through its internal ADC sampling channel, and calculates the real-time grid-connected power value of itself based on these data; in the preferred embodiment, the micro grid-connected inverter calculates and updates its real-time grid-connected power every power frequency cycle (20ms at 50Hz) according to the ADC sampling value, without the need for query instruction triggering, making the entire control process simpler.

[0035] The second Wi-Fi communication module of the micro grid-connected inverter constructs a TCP response data packet containing its own device ID and the calculated real-time grid-connected power data, and sends the data packet to the IP address of the first Wi-Fi communication module of the reverse flow prevention ammeter; the first Wi-Fi communication module of the reverse flow prevention ammeter receives the TCP response data packet and transmits it to the main control MCU through a serial interface; the main control MCU parses the TCP response data packet, extracts the device ID and real-time grid-connected power data therein, and updates the power value of the corresponding micro grid-connected inverter in its internal register according to the device ID, thereby completing the collection and update of the power data.

[0036] The communication process shown in this embodiment combines the efficiency of UDP broadcast and the reliability of TCP transmission, ensuring that the reverse flow prevention ammeter can timely, accurately and orderly obtain the real-time running data of all micro grid-connected inverters in a local area network environment.

[0037] In some embodiments, the required power adjustment instruction is calculated according to the sum of the real-time reverse flow power and the real-time grid-connected power of the micro grid-connected inverter, including: The reverse flow prevention ammeter reads the real-time reverse flow power value and the total grid-connected power value after the real-time grid-connected power of the micro grid-connected inverter is summed up; judging the sign of the real-time reverse power value; If the real-time reverse power value is positive, indicating that the grid delivers power to the user, an instruction to increase the output power or maintain the current state is generated. If the real-time reverse power value is negative, indicating that there is reverse power, the absolute value of the reverse power is calculated. The absolute value of the reverse power is used as the total amount of power adjustment required. According to the ratio of the total amount of power adjustment to the total grid-connected power value, the power down percentage instruction is calculated.

[0038] The embodiment details the specific process of calculating the required power adjustment instruction by the anti-reverse flow meter based on the sum of the real-time reverse power and the real-time grid-connected power of all micro grid-connected inverters (i.e. total grid-connected power). Specifically, the anti-reverse flow meter reads the real-time reverse power value stored in its internal memory and the total grid-connected power value obtained by aggregating the reported power of each micro grid-connected inverter. The core processing unit of the anti-reverse flow meter judges the sign of the real-time reverse power value: if the result is positive, it indicates that the power is normally delivered from the grid to the user, and there is no reverse flow phenomenon, at which time an instruction is generated to allow the micro grid-connected inverter to increase the output power or maintain the current state; if the result is negative, it confirms that there is reverse power, and immediately calculates the absolute value of the reverse power. On this basis, the anti-reverse flow meter further intelligently calculates the total amount of power adjustment required based on the weighted sum of the absolute value of the reverse power and the real-time monitoring rate of the reverse power change, and finally calculates the unified power down percentage instruction according to the accurate ratio of the total amount of power adjustment to the total grid-connected power value.

[0039] This embodiment introduces the reverse power change rate as a dynamic parameter for forward-looking adjustment, and combines the proportional calculation method to ensure that when the reverse power is negative, all normally working micro grid-connected inverters in the local area network can simultaneously increase the power by the same accurate proportion until the reverse power rises close to zero; when the reverse power is positive, all micro grid-connected inverters simultaneously reduce the power by the same proportion until the reverse power is eliminated. This avoids the problem of repeated power oscillation caused by directly taking the rated power as the target, significantly improving the stability and accuracy of control.

[0040] In some embodiments, the micro grid-connected inverter receives the power adjustment instruction and adjusts its output power according to the power adjustment instruction to make the real-time reverse power approach zero, including: The second Wi-Fi communication module listens to and receives the broadcast data packet from the anti-reverse flow meter; The data packet is parsed to extract the power adjustment instruction, and the corresponding operation is performed according to the type of the power adjustment instruction, including: If it is a power down percentage instruction, the output power value to be reduced is calculated according to the product of the power down percentage and the current output power; If it is a power up instruction, the output power reference value is gradually increased according to a preset power ramping rate, and the output power reference value is converted into actual AC output power; The micro-grid-connected inverter continuously updates the power adjustment instruction until a new instruction is received or the real-time reverse flow power approaches zero.

[0041] In this embodiment, the second Wi-Fi communication module of the micro-grid-connected inverter continuously listens to and receives the broadcast data packet broadcasted by the anti-reverse flow meter through the local area network; the main control chip of the micro-grid-connected inverter parses the broadcast data packet and extracts the power adjustment instruction contained therein, and performs corresponding operations according to the specific type of the power adjustment instruction: If the parsed instruction type is a power down percentage instruction, the main control chip accurately calculates the output power value to be reduced according to the product of the power down percentage and the current output power of the micro-grid-connected inverter; If the parsed instruction type is a power up instruction, the main control chip gradually and smoothly increases the output power reference value according to the internally preset power ramping rate; The micro-grid-connected inverter converts the output power reference value into actual AC output power by changing the modulation strategy of its internal pulse width modulation module; The micro-grid-connected inverter continuously performs the above-mentioned response to the power adjustment instruction and output power update operation until it receives a new power adjustment instruction or confirms through feedback that the real-time reverse flow power has approached zero.

[0042] This embodiment ensures that all micro-grid-connected inverters can synchronously, accurately and smoothly respond to the control commands of the anti-reverse flow meter, quickly eliminate the reverse flow phenomenon through coordinated power regulation actions, and at the same time avoid the impact of power mutation on the power grid, ensuring stability and reliability.

[0043] In some embodiments, a local router is further included, and the first Wi-Fi communication module and the second Wi-Fi communication module are both connected to the local router to form a local area network.

[0044] In this embodiment, the local router serves as a communication hub and provides a high-speed, stable and low-latency data transmission channel between the anti-reverse flow meter and all micro-grid-connected inverters. Through the formation of a local area network, communication between all devices, including state query requests, power data reporting and broadcast sending of power adjustment instructions, is completed within this private network, ensuring the real-time and reliability of data transmission, while avoiding dependence on external Internet, enhancing independence and security.

[0045] In some embodiments, the grid voltage sampling terminal is used to connect a single-phase power grid to detect the grid voltage parameters, including: The grid voltage sampling terminal is directly connected to the live wire and the neutral wire of the single-phase power grid through a high-resistance voltage dividing resistor network; The output end of the voltage dividing resistor network is connected to a voltage follower circuit composed of an operational amplifier, which is used to realize impedance matching and signal isolation; The output of the voltage follower is connected to the input channel of the analog-to-digital converter; The analog-to-digital converter converts the analog voltage signal into a digital quantity and transmits it to the reverse current meter; The reverse current meter software calibrates the digital quantity and calculates the effective value, frequency and phase angle of the grid voltage, which are the grid voltage parameters.

[0046] In this embodiment, the grid voltage sampling terminal is directly connected to the live wire and the neutral wire of the single-phase power grid through a high-resistance voltage dividing resistor network, realizing the safe acquisition of high-voltage grid signals; the output end of the voltage dividing resistor network is connected to a voltage follower circuit composed of an operational amplifier, which is used to realize impedance matching and signal isolation, ensuring the stability of the sampling signal; the output of the voltage follower circuit is connected to the input channel of the analog-to-digital converter, completing the transmission of the analog signal; the analog-to-digital converter converts the received analog voltage signal into a digital quantity and transmits it to the main control unit of the reverse current meter through the data interface; the main control unit of the reverse current meter software calibrates the received digital quantity and calculates the effective value, frequency and phase angle of the grid voltage through an algorithm, which together constitute the grid voltage parameters.

[0047] This embodiment ensures the safety of high-voltage sampling through a high-resistance voltage dividing resistor network, improves signal quality through a voltage follower circuit, and finally obtains accurate grid voltage parameters through analog-to-digital conversion and software processing, providing an accurate voltage reference and ensuring the accuracy of basic measurements.

[0048] In some embodiments, the current measurement signal input terminal is used to connect a current transformer to obtain a signal reflecting the size of the incoming / outgoing current of the power grid, denoted as the current signal, including: The current measurement signal input terminal is connected to the secondary side output terminal of the external current transformer, and the primary side of the external current transformer is connected in series to the live wire of the user's power grid total inlet; A precision sampling resistor is included in the input loop of the current measurement signal input terminal, which is used to convert the current signal output by the current transformer into a voltage signal; The voltage signal is amplified and level shifted by a differential amplifier circuit composed of an operational amplifier, and is transformed to the input voltage range required by the analog-to-digital converter; The analog-to-digital converter converts the amplified analog voltage signal into a digital quantity and transmits it to the reverse current meter; The reverse current meter software calibrates the digital quantity and, in combination with the phase angle of the grid voltage parameter, calculates the current effective value and power direction flowing into or out of the grid, recorded as a current signal.

[0049] In this embodiment, the current measurement signal input terminal is connected to the secondary side output terminal of the external current transformer, and the primary side of the external current transformer is connected in series with the live wire at the total entrance of the user's power grid for real-time detection of the total current signal. A precision sampling resistor is included in the input loop of the current measurement signal input terminal for converting the current signal output by the current transformer into a voltage signal. The voltage signal is amplified and level shifted by a differential amplifier circuit composed of an operational amplifier to convert it to the input voltage range required by the analog-to-digital converter. The analog-to-digital converter converts the amplified analog voltage signal into a digital quantity and transmits it to the main control unit of the reverse current meter through a data interface. The main control unit of the reverse current meter software calibrates the received digital quantity and, in combination with the phase angle of the grid voltage parameter, calculates the current effective value and power direction flowing into or out of the grid through an algorithm. These parameters together constitute the current signal.

[0050] This embodiment realizes non-contact current detection through the current transformer, ensuring safety of sampling. Precise conversion and conditioning of the signal are achieved through the precision sampling resistor and the differential amplifier circuit. After analog-to-digital conversion and digital processing, in combination with voltage phase information, the complete current signal containing size and direction is finally obtained, providing a reliable basis for current data and ensuring accuracy and reliability.

[0051] In some embodiments, the reverse current meter is configured to calculate real-time reverse current power based on the grid voltage parameter and the current signal, including: The reverse current meter multiplies the sampled grid voltage instantaneous value and the current instantaneous value to obtain an instantaneous power value; and integrates the instantaneous power value over one grid fundamental period and takes the average to obtain the active power value of the current period; According to the phase relationship between the current signal and the grid voltage parameter, the power flow direction is determined, including: When the current phase lags behind the voltage phase, it is determined that the active power is in the positive direction, i.e., the grid delivers power to the user; When the current phase leads the voltage phase, it is determined that the active power is in the reverse direction, i.e., the user delivers power to the grid, recorded as reverse current power; The active power value and the power direction information are combined to generate a signed real-time reverse current power value, with a positive sign indicating that the grid delivers power to the user and a negative sign indicating that there is reverse current power.

[0052] In this embodiment, the main control unit of the reverse current prevention ammeter performs real-time multiplication operation on the sampled grid voltage instantaneous value and current instantaneous value to obtain an instantaneous power value; the main control unit of the reverse current prevention ammeter performs integral operation on the instantaneous power value within one grid fundamental cycle, and calculates the average value of the integral result to obtain the active power value of the current cycle; the main control unit of the reverse current prevention ammeter determines the power flow direction according to the phase relationship between the current signal and the grid voltage parameter, which specifically includes: When it is detected that the current phase lags behind the voltage phase, it is determined that the active power is in the positive direction, that is, the grid supplies power to the user; When it is detected that the current phase leads the voltage phase, it is determined that the active power is in the reverse direction, that is, the user supplies power to the grid, and this case is recorded as reverse current power; The main control unit of the reverse current prevention ammeter combines the calculated active power value and the power direction information to generate a signed real-time reverse current power value, wherein the positive sign indicates that the grid supplies power to the user, and the negative sign indicates that there is reverse current power.

[0053] The embodiment accurately obtains the active power value by the method of instantaneous power calculation and cycle integration, accurately determines the power direction in combination with the voltage and current phase relationship, and finally generates a signed real-time reverse current power value, thereby ensuring the accuracy and real-time performance of the reverse current prevention control.

[0054] In some embodiments, the reverse current prevention ammeter and the micro-grid-connected inverter communicate through UDP protocol or TCP protocol.

[0055] In some embodiments, the period of the reverse current prevention ammeter performing the query, calculation and broadcast sending operations is 0.2-2 seconds.

[0056] Specifically, the above embodiment can be divided into the following steps: The micro-grid-connected inverter with a built-in wifi module can access a local router; A reverse current prevention ammeter with a built-in wifi module, which can communicate with the micro-inverter through wifi and access a local router; The reverse current prevention ammeter has two input ports: one input port connects a single-phase grid for detecting grid voltage; the other port connects a CT output voltage, which reflects the current flowing into / out of the grid. The reverse current prevention ammeter calculates the power flowing into / out of the grid according to the grid voltage and the CT output voltage.

[0057] The reverse current prevention ammeter periodically queries the working state and actual grid-connected power of each micro-grid-connected inverter, and calculates the power percentage that the micro-inverter needs to be adjusted according to the detected reverse current power; The reverse current prevention ammeter periodically broadcasts the power percentage that the micro-grid-connected inverter needs to be adjusted to the micro-inverters in the local area network; The micro-grid-connected inverter in the local area network can control its grid-connected power according to the received meter information.

[0058] When the anti-reverse flow meter power is positive, it indicates that the micro-grid-connected inverter outputs power to the grid, and at this time the micro-grid-connected inverter needs to reduce the power; when the reverse flow power is negative, it indicates that the grid outputs power, and at this time the micro-grid-connected inverter can increase the power until the reverse flow power rises close to 0.

[0059] That is, when the reverse flow power is negative, all micro-grid-connected inverters in the local area network simultaneously increase the power by the same proportion until the reverse flow power rises close to 0w.

[0060] When the reverse flow power is positive, all micro-grid-connected inverters in the local area network simultaneously reduce the power by the same proportion until the reverse flow power drops below 0w.

[0061] The embodiment realizes efficient, fast and accurate anti-reverse flow function by using the anti-reverse flow meter as a unified control host and coordinating the micro-grid-connected inverters in the local area network as slaves, fully meets the stringent grid-connected standard requirements, and can instruct the micro-grid-connected inverters to quickly raise the power to the maximum power point when no reverse flow occurs, thereby maximizing the avoidance of energy waste. Through the intelligent percentage calculation strategy based on real-time power and change rate, precise cooperative control of multiple micro-grid-connected inverters is realized, power loss in the traditional control mode is effectively reduced, the master-slave architecture limitation is broken, the flexibility of application is enhanced, and reliable protection is provided for the safe, stable and efficient operation of the photovoltaic grid-connected system.

[0062] In the above technical solution, the system composed of the anti-reverse flow meter and at least one micro-grid-connected inverter through a local router to form a local area network, the anti-reverse flow meter accurately obtains the grid parameters through its grid voltage sampling terminal and current measurement signal input terminal, and periodically queries the real-time grid-connected power of each micro-grid-connected inverter as a control center, calculates and broadcasts power adjustment instructions, and finally drives all micro-grid-connected inverters to adjust the output synchronously. By using the anti-reverse flow meter as a unified control core, the unified power adjustment instruction is calculated based on the real-time reverse flow power and the total generated power, so that all micro-invers can be adjusted in synchronization and proportion, precise cooperative control of multiple micro-invers is realized, and power oscillation is avoided; the smooth proportional down-regulation mode is adopted instead of complete shutdown, the amount of self-generated and self-used electricity is maximized, and energy loss is significantly reduced; the master-slave architecture limitation is broken, all micro-invers are equal, users can flexibly expand according to needs, and the application limitation problem is solved; the entire control closed loop operates in a high-speed local area network, responds quickly, meets the grid-connected standard requirements for eliminating reverse flow, and effectively protects the safe operation of the grid.

[0063] Finally, it should be noted that the above embodiments have been described in the specification and drawings of the application, but this does not limit the patent protection scope of the application. Any equivalent structure or equivalent process replacement or modification based on the essential concept of the application, using the content described in the specification and drawings of the application, and directly or indirectly implementing the technical solutions of the above embodiments in other related technical fields, etc., are all included in the patent protection scope of the application.

Claims

1. A reverse current prevention device suitable for micro grid-connected inverter systems, characterized in that, include: The anti-backflow meter has a first Wi-Fi communication module, a grid voltage sampling terminal, and a current measurement signal input terminal. The first Wi-Fi communication module is used to access a local router and form a local area network. The grid voltage sampling terminal is used to connect to a single-phase grid to detect grid voltage parameters. The current measurement signal input terminal is used to connect to a current transformer to obtain a signal reflecting the magnitude of the grid inflow / outflow current, denoted as a current signal. The anti-backflow meter is configured to calculate the real-time backflow power based on the grid voltage parameters and current signal. At least one miniature grid-connected inverter, each of the miniature grid-connected inverters having a second Wi-Fi communication module, the second Wi-Fi communication module being used to access the local router and be in the same local area network as the anti-reverse current meter; The anti-backflow meter periodically queries and obtains the real-time grid-connected power of the micro grid-connected inverter through the local area network; The required power adjustment command is calculated based on the sum of the real-time reverse current power and the real-time grid-connected power of all the micro grid-connected inverters. The power adjustment command is broadcast over the local area network. The micro grid-connected inverter receives the power adjustment command and adjusts its own output power according to the power adjustment command so that the real-time reverse current power approaches zero.

2. The anti-reverse current device for micro grid-connected inverter systems according to claim 1, characterized in that, The anti-backflow meter periodically queries and obtains the real-time grid-connected power of the micro grid-connected inverter through the local area network, including: The main control MCU of the anti-backflow meter drives the first Wi-Fi communication module through an SPI or UART interface; The first Wi-Fi communication module constructs and sends a status query request data frame based on the UDP broadcast protocol. The destination address of the status query request data frame is the local area network broadcast address, and the status query request data frame has an instruction code. The main control chip of the micro grid-connected inverter captures and parses the status query request data frame through the Wi-Fi firmware stack; After confirming the instruction code, the current and voltage sensor data on the inverter output bridge arm are read through the ADC sampling channel to calculate its real-time grid-connected power. Alternatively, the micro grid-connected inverter calculates and updates its real-time grid-connected power based on the ADC sampling value each power frequency cycle; The second Wi-Fi communication module constructs a TCP response data packet containing its own device ID and real-time grid-connected power data, and sends it to the IP address of the first Wi-Fi communication module; The first Wi-Fi communication module receives the TCP response data packet and transmits it to the main control MCU through the serial interface; The main control MCU parses the data packet and updates the power value of the corresponding micro grid-connected inverter in its internal register according to the device ID in the packet.

3. The anti-reverse current device for micro grid-connected inverter systems according to claim 1, characterized in that, Based on the sum of the real-time reverse current power and the real-time grid-connected power of the micro grid-connected inverter, the required power adjustment command is calculated, including: The anti-backflow meter reads the real-time backflow power value and the total grid-connected power value after summing the real-time grid-connected power of the micro grid-connected inverter; Determine the sign of the real-time reverse current power value; If the real-time reverse power value is positive, it means that the power grid is transmitting power to the user, and then an instruction is generated to increase the output power or maintain the current state. If the real-time reverse current power value is negative, it indicates that reverse current power exists, then the absolute value of the reverse current power is calculated; The absolute value of the reverse current power is taken as the total required power adjustment; The power reduction percentage instruction is calculated based on the ratio of the total power adjustment amount to the total grid-connected power value.

4. The anti-reverse current device for micro grid-connected inverter systems according to claim 1, characterized in that, The micro grid-connected inverter receives the power adjustment command and adjusts its own output power according to the power adjustment command to make the real-time reverse current power approach zero, including: The second Wi-Fi communication module listens for and receives broadcast data packets from the anti-reverse current meter; Parse the data packet, extract the power adjustment instruction, and perform corresponding operations according to the type of the power adjustment instruction, including: If it is a power reduction percentage command, the required reduction in output power is calculated by multiplying the power reduction percentage by the current output power. If it is a power increase command, the output power reference value is gradually increased according to the preset power ramp rate, and the output power reference value is converted into the actual AC output power. The micro grid-connected inverter continuously updates the power adjustment command until it receives a new command or the real-time reverse current power approaches zero.

5. The anti-reverse current device for a micro grid-connected inverter system according to claim 1, characterized in that, It also includes a local router, and both the first Wi-Fi communication module and the second Wi-Fi communication module are connected to the local router to form the local area network.

6. The anti-reverse current device for a micro grid-connected inverter system according to claim 1, characterized in that, The grid voltage sampling terminal is used to connect to a single-phase grid to detect grid voltage parameters, including: The grid voltage sampling terminal is directly connected to the live wire and neutral wire of a single-phase power grid through a high-resistance voltage divider network; The output of the voltage divider resistor network is connected to a voltage follower circuit composed of an operational amplifier to achieve impedance matching and signal isolation. The output of the voltage follower is connected to the input channel of the analog-to-digital converter; The analog-to-digital converter converts the analog voltage signal into a digital quantity and transmits it to the anti-reverse current meter; The anti-reverse current meter performs software calibration on the digital quantity and calculates the effective value, frequency, and phase angle of the grid voltage, which are the grid voltage parameters.

7. The anti-reverse current device for a micro grid-connected inverter system according to claim 1, characterized in that, The current measurement signal input terminal is used to connect to a current transformer to obtain a signal reflecting the magnitude of the current flowing into / out of the power grid, denoted as the current signal, including: The current measurement signal input terminal is connected to the secondary output terminal of the external current transformer, and the primary side of the external current transformer is clamped in series to the live wire of the user's main power grid inlet. The input circuit of the current measurement signal input terminal includes a precision sampling resistor, which is used to convert the current signal output by the current transformer into a voltage signal. The voltage signal is amplified and level-shifted by a differential amplifier circuit composed of operational amplifiers, and transformed to the input voltage range required by the analog-to-digital converter. The analog-to-digital converter converts the amplified analog voltage signal into a digital quantity and transmits it to the anti-reverse current meter. The anti-reverse current meter performs software calibration on the digital quantity and, in conjunction with the phase angle of the grid voltage parameters, calculates the effective value and power direction of the current flowing into or out of the grid, which is recorded as a current signal.

8. The anti-reverse current device for a micro grid-connected inverter system according to claim 1, characterized in that, The anti-backflow meter is configured to calculate the real-time backflow power based on the grid voltage parameters and current signal, including: The anti-reverse current meter multiplies the sampled instantaneous grid voltage value and the instantaneous current value to obtain the instantaneous power value; Furthermore, the instantaneous power value is integrated within one fundamental cycle of the power grid, and the average value is calculated to obtain the active power value of the current cycle. Based on the phase relationship between the current signal and the grid voltage parameters, the direction of power flow is determined, including: When the current phase lags behind the voltage phase, it is determined to be in the positive direction of active power, that is, the power grid is transmitting power to the user; When the current phase leads the voltage phase, it is determined that the active power is in the opposite direction, that is, the user is transmitting power to the grid, which is recorded as reverse power. The active power value is combined with the power direction information to generate a signed real-time reverse power value. A positive sign indicates that the power grid is transmitting power to the user, and a negative sign indicates that there is reverse power.

9. The anti-reverse current device for a micro grid-connected inverter system according to claim 1, characterized in that, The anti-reverse current meter communicates with the micro grid-connected inverter via UDP or TCP protocols.

10. The anti-reverse current device for a micro grid-connected inverter system according to claim 1, characterized in that, The anti-backflow meter periodically performs query, calculation, and broadcast transmission operations every 0.2 to 2 seconds.

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