Adaptive Transmission System for Photovoltaic Power Plant Operation Based on Satellite Narrowband Communication

Abstract

This invention relates to the field of communication technology for new energy operation and maintenance, and discloses an adaptive transmission system for photovoltaic power plant operation based on narrowband satellite communication, including modules for state perception, synchronization interference prediction, transmission parameter configuration, and adaptive framing. The system first collects the mechanical tilt angle of the photovoltaic support and satellite ephemeris, calculates the satellite projection elevation angle, and combines it with component reflection properties to generate a synchronization quality index reflecting the quality of navigation signal locking. Then, it establishes a mapping relationship between this index and uplink capability, generates a transmission availability coefficient, and dynamically sets the net payload quota and error correction redundancy for the transmission cycle accordingly. Finally, based on the availability coefficient, it calculates the semantic urgency and priority of various monitoring data, and sorts, truncates, and performs variable-length framing of the data.

Description

Technical Field

[0001] This invention relates to the field of new energy operation and maintenance communication technology, and more specifically, to an adaptive transmission system for photovoltaic power plant operation based on satellite narrowband communication. Background Technology

[0002] With the large-scale development of the new energy industry, large-scale ground-mounted photovoltaic power plants are typically built in remote areas such as the Gobi Desert, barren land, or mountainous regions, where sunlight is abundant but the location is remote. To centrally manage these dispersed power assets in harsh environments, operators need to collect key operation and maintenance data in real time, such as inverter status, power generation, and meteorological conditions. Since remote areas often lack terrestrial cellular network coverage, satellite IoT based on non-terrestrial networks has become the primary means of remote monitoring of these power plants. In narrowband satellite communication systems, the uplink transmission of terminal devices strictly relies on high-precision time-frequency synchronization. Specifically, before initiating a connection or transmitting data, the terminal must obtain its precise position and timing information through the Global Navigation Satellite System (GNSS) and calculate Doppler frequency shift and timing advance using satellite ephemeris data to pre-compensate the signal. If the terminal cannot lock onto the GNSS signal or the positioning error is too large, uplink synchronization will fail, preventing access to the satellite network. However, in large photovoltaic power plants using single-axis tracking brackets, communication terminals are typically installed next to the combiner box or inverter adjacent to the photovoltaic module array. Photovoltaic modules typically have surfaces made of smooth materials like glass, creating a highly reflective mirror environment when laid out over large areas. Unlike stationary buildings, single-axis tracking supports drive the photovoltaic array to perform periodic angular adjustments to follow the sun's position throughout the day. Current satellite communication terminals often ignore the dynamic impact of this photovoltaic environment on navigation signals during data transmission. In fact, when the mechanical tilt angle of the photovoltaic array and the incident angle of the navigation satellite satisfy a specific geometric relationship, the signal reflected by the array superimposed on the direct signal, creating a severe multipath effect that causes a sharp drop in the carrier-to-noise ratio of the navigation signal, even leading to signal loss. This signal decay caused by array movement exhibits a clear time-varying pattern, but existing communication mechanisms typically treat it as random interference, lacking targeted avoidance strategies. When in a signal decay window, terminal equipment often repeatedly attempts to search for satellites and retransmit, not only causing critical alarm data to fail to be sent in a timely manner but also resulting in additional power consumption due to ineffective radio frequency transmissions. In addition, existing data transmission protocols typically use fixed frame formats and transmission priorities, which cannot dynamically adjust the weight of data content and error correction capabilities according to the degree of channel condition deterioration. As a result, high-value operation and maintenance data (such as fault alarms) are easily discarded or overwhelmed under weak signal windows. Summary of the Invention

[0003] This invention provides an adaptive transmission system for photovoltaic power plant operation based on satellite narrowband communication, which solves the technical problems mentioned in the background art.

[0004] This invention provides an adaptive transmission system for photovoltaic power plant operation based on satellite narrowband communication, comprising: The status perception module is used to collect the current mechanical tilt angle and mechanical tilt angle change rate of the single-axis tracking bracket of the photovoltaic power station in real time, obtain the satellite ephemeris data of the visible navigation satellites in the current period, and receive the station operation monitoring data to be sent. The synchronization interference prediction module is used to calculate the satellite projection elevation angle based on the current mechanical tilt angle and the satellite ephemeris data, calculate the dominant multipath phase difference of the navigation satellite signal in combination with the specular reflection characteristics of the photovoltaic module reflector, and generate a synchronization quality index reflecting the locking quality of the navigation signal based on the dominant multipath phase difference. The transmission parameter configuration module is used to establish the mapping relationship between the synchronization quality index and the uplink transmission capacity to generate the transmission availability coefficient, and to set the net payload byte quota and error correction coding redundancy of the current transmission cycle based on the transmission availability coefficient. An adaptive framing module is used to calculate the transmission priority of the site operation monitoring data based on the transmission availability coefficient, sort the site operation monitoring data according to the transmission priority, extract data segments based on the payload byte quota, and assemble a reordered data frame containing variable-length data payload and variable-length redundancy check code by combining the error correction coding redundancy.

[0005] The beneficial effects of this invention are as follows: By introducing the mechanical tilt angle of the photovoltaic support as the core input variable of the communication system, the multipath interference caused by the movement of the photovoltaic array is transformed from a random and uncontrollable factor into a predictable variable. The system utilizes the geometric relationship between the projection elevation angle and the reflective surface of the components to identify vulnerable windows of navigation signals in advance and dynamically adjusts the allocation strategy of transmission resources through a continuous mapping mechanism. This mechanism enables the communication terminal to proactively compress non-critical data, prioritize high-value alarm data, and increase error correction redundancy before channel conditions deteriorate, thereby avoiding energy loss and connection interruptions caused by blind retransmissions in traditional mechanisms. This invention effectively solves the problem of satellite narrowband communication instability caused by the synchronous movement of the array in large photovoltaic power plants, significantly improving the success rate of operation and maintenance data transmission and system robustness in complex electromagnetic environments. Attached Figure Description

[0006] Figure 1 This is a block diagram of the adaptive transmission system for photovoltaic power plant operation based on satellite narrowband communication of the present invention; Figure 2 This is a schematic diagram of the satellite communication signal propagation scenario of the single-axis tracking photovoltaic power station of the present invention. Detailed Implementation

[0007] The subject matter described herein will now be discussed with reference to exemplary embodiments. It should be understood that these embodiments are discussed only to enable those skilled in the art to better understand and implement the subject matter described herein, and changes may be made to the function and arrangement of the elements discussed without departing from the scope of this specification. Various processes or components may be omitted, substituted, or added as needed in the examples. Furthermore, features described in some examples may be combined in other examples.

[0008] It should be noted that, unless otherwise defined, the technical or scientific terms used in one or more embodiments of the present invention should have the ordinary meaning understood by one of ordinary skill in the art to which this invention pertains. The terms "first," "second," and similar terms used in one or more embodiments of the present invention do not indicate any order, quantity, or importance, but are merely used to distinguish different components. Terms such as "include" or "comprising" indicate that the element or object preceding the term encompasses the element or object listed following the term and its equivalents, without excluding other elements or objects. Terms such as "connected" or "linked" are not limited to physical or mechanical connections, but can include electrical connections, whether direct or indirect. Terms such as "up," "down," "left," and "right" are used only to indicate relative positional relationships; when the absolute position of the described object changes, the relative positional relationship may also change accordingly.

[0009] like Figure 1 As shown, the adaptive transmission system for photovoltaic power plant operation based on satellite narrowband communication includes: The status perception module is used to collect the current mechanical tilt angle and mechanical tilt angle change rate of the single-axis tracking bracket of the photovoltaic power station in real time, obtain the satellite ephemeris data of the visible navigation satellites in the current period, and receive the station operation monitoring data to be sent. The synchronization interference prediction module is used to calculate the satellite projection elevation angle based on the current mechanical tilt angle and the satellite ephemeris data, calculate the dominant multipath phase difference of the navigation satellite signal in combination with the specular reflection characteristics of the photovoltaic module reflector, and generate a synchronization quality index reflecting the locking quality of the navigation signal based on the dominant multipath phase difference. The transmission parameter configuration module is used to establish the mapping relationship between the synchronization quality index and the uplink transmission capacity to generate the transmission availability coefficient, and to set the net payload byte quota and error correction coding redundancy of the current transmission cycle based on the transmission availability coefficient. An adaptive framing module is used to calculate the transmission priority of the site operation monitoring data based on the transmission availability coefficient, sort the site operation monitoring data according to the transmission priority, extract data segments based on the payload byte quota, and assemble a reordered data frame containing variable-length data payload and variable-length redundancy check code by combining the error correction coding redundancy.

[0010] The synchronization interference prediction module calculates the satellite projection elevation angle based on the current mechanical tilt angle and the satellite ephemeris data, specifically including the calculation according to the following formula: In the formula, Indicates time No. The satellite projection elevation angle of the navigation satellite; Represents the bivariate arctangent function; This indicates the time calculated based on the satellite ephemeris data. No. The celestial component of a navigation satellite in the station-centered coordinate system; This indicates the time calculated based on the satellite ephemeris data. No. The eastward component of a navigation satellite in the station-centric coordinate system; This represents the absolute value operation; This represents a very small positive constant used to prevent division by zero errors.

[0011] The current mechanical tilt angle is the pitch angle of the single-axis tracking bracket of the photovoltaic power station during real-time operation. It can be obtained through the angle sensor and controller of the single-axis tracking bracket, or by reading it from the bracket control system using the Modbus protocol.

[0012] Satellite ephemeris data is data broadcast by navigation satellites that includes information such as satellite orbit and clock bias, and is used to calculate the satellite's real-time position. It can be obtained by receiving broadcast ephemeris or precise ephemeris data sent by navigation satellites using a GNSS receiver.

[0013] The satellite line-of-sight vector in the station-centered coordinate system is the vector pointing to the satellite with the center point of the photovoltaic power station as the origin, after the satellite ephemeris data has been converted.

[0014] The horizontal component of the plane perpendicular to the tracking axis of the single-axis tracking bracket of the photovoltaic power station is the component of the satellite line-of-sight vector in that plane along the east-west direction.

[0015] The vertical component of the plane perpendicular to the tracking axis of the single-axis tracking bracket of the photovoltaic power station is the component of the satellite line-of-sight vector along the zenith direction in that plane.

[0016] The satellite projection elevation angle is an angle obtained by performing an arctangent operation on the absolute values ​​of the vertical and horizontal components. It is used to characterize the incident angle relationship between the satellite and the reflective surface of the photovoltaic module.

[0017] The zero-prevention minimum value δ is a very small positive value set to avoid errors where the denominator is zero during calculation. It is preferably 1 × 10⁻⁶. -12 This value is small enough that it will not affect the accuracy of the calculation results, and at the same time, it can effectively avoid division by zero errors and ensure the stability of numerical calculations.

[0018] The station center coordinate system adopts the northeast-north-sky coordinate system, that is, the east is the X-axis, the north is the Y-axis, and the zenith is the Z-axis. This coordinate system is a commonly used standard coordinate system for photovoltaic power station positioning and satellite geometric calculation, and can accurately describe the positional relationship of the satellite relative to the station.

[0019] The plane perpendicular to the tracking axis of the single-axis tracking bracket is specifically the east-west celestial plane, because the tracking axis of the single-axis tracking bracket is usually in the north-south direction. The plane perpendicular to the north-south tracking axis is the east-west celestial plane, which can accurately match the motion characteristics of the single-axis bracket that rotates only in the east-west direction.

[0020] The horizontal (east-west direction) and vertical (zenith direction) components of the satellite line-of-sight vector within the east-west sky plane are extracted because the reflection geometry of the single-axis tracking support is only related to the incident angle of the satellite in that plane; components in other directions do not affect the effect of component reflection on GNSS signals.

[0021] By using the arctangent of the absolute values ​​of the vertical and horizontal components, satellite signals from different azimuth angles can be mapped onto the same east-west sky plane, eliminating azimuth interference. For example, two satellites with different azimuth angles but the same incident angle in the east-west sky plane will have the same projected elevation angle after projection, ensuring that subsequent reflection geometry calculations are only related to the support tilt angle, which conforms to the motion law of single-axis tracking.

[0022] The specific method for converting satellite ephemeris data into a satellite line-of-sight vector in a station-centered coordinate system is as follows: First, calculate the satellite's geocentric rectangular coordinates using the satellite ephemeris data. Then, combine this with the latitude, longitude, and altitude data of the photovoltaic power station, and use a coordinate transformation matrix to convert the geocentric rectangular coordinates to northeast station-centered coordinates, thereby obtaining the satellite line-of-sight vector. The conversion process requires precise location information of the power station, which can be obtained through pre-calibration of a GNSS receiver.

[0023] The plane perpendicular to the tracking axis of the single-axis tracking bracket is the east-west celestial plane. The tracking axis (north-south direction) is the normal of this plane. The horizontal component corresponds to the east-west direction, and the vertical component corresponds to the zenith direction. Component extraction can be achieved by projecting the satellite line-of-sight vector onto the normal vector of this plane.

[0024] The preferred value for preventing the zero minimum δ is 1×10. -12 This value is widely used in engineering calculations because it avoids calculation errors caused by a zero denominator and does not affect the accuracy of the angle calculation results.

[0025] The arctangent operation uses a bivariate arctangent function, which can directly determine the quadrant of the angle based on the sign of the vertical and horizontal components, ensuring that the calculated satellite projection elevation angle is between 0 and 90 degrees.

[0026] The synchronization interference prediction module calculates the dominant multipath phase difference of the navigation satellite signal by combining the specular reflection characteristics of the photovoltaic module's reflective surface, specifically by calculating according to the following formula: In the formula, Indicates time No. The dominant multipath phase difference value of the navigation satellite; Represents pi; This represents the equivalent height difference between the phase center of the navigation satellite receiving antenna and the dominant reflective surface of the photovoltaic module; This indicates the carrier wavelength of the navigation satellite signal; Represents the sine function; Indicates time-based No. The satellite projection elevation angle of the navigation satellite; Indicates time The current mechanical tilt angle.

[0027] The equivalent height difference is the vertical distance from the phase center of the navigation satellite receiving antenna to the dominant reflector of the photovoltaic module. It can be measured directly with a laser rangefinder, or by measuring the height from the antenna phase center to the ground and the height from the dominant reflector to the ground with a measuring tape; the difference between the two is the equivalent height difference.

[0028] The carrier wavelength of a navigation satellite signal is the spatial length corresponding to the carrier oscillation period of the transmitted signal. It is preferably 0.1903 meters, based on the carrier wavelength of the Global Positioning System (GPS) L1 band. This band is commonly used by navigation satellites, has wide engineering applications, and its parameters are highly versatile.

[0029] The angle difference is the numerical difference between the satellite projection elevation angle and the current mechanical tilt angle collected by the state perception module.

[0030] The dominant multipath phase difference is a physical quantity that reflects the phase difference between the direct signal from the navigation satellite and the reflected signal from the photovoltaic module.

[0031] The specular reflection characteristics of the reflective surface of photovoltaic modules cause navigation satellite signals to form reflected signals with fixed paths. The phase difference between the reflected signal and the direct signal directly affects the carrier-to-noise ratio of the received signal.

[0032] The calculation of the dominant multipath phase difference by coupling the equivalent height difference, carrier wavelength, angle difference, and pi is essentially derived from the path difference formula based on specular reflection. There is a fixed conversion relationship between path difference and phase difference: the phase difference equals the product of the path difference and wavelength (twice the value of pi). In the case of a photovoltaic power station, the path difference can be approximated by the sine of the equivalent height difference and angle difference. For example, when the satellite projection elevation angle is 30 degrees and the current mechanical tilt angle is 20 degrees, the angle difference is 10 degrees, with a sine value of approximately 0.1736. Combining this with an equivalent height difference of 1.2 meters and a carrier wavelength of 0.1903 meters, the corresponding path difference and phase difference can be calculated, accurately quantifying the intensity of multipath interference.

[0033] The dominant reflective surface of a photovoltaic module is defined as the center line of the glass surface of the row of photovoltaic modules closest to the navigation satellite receiving antenna, thus avoiding interference caused by multiple reflective surfaces.

[0034] The equivalent height difference must be measured when the photovoltaic modules are in a horizontal position. First, measure the vertical height from the antenna phase center to the ground, and then measure the vertical height from the center line of the glass surface of the nearest row of modules to the ground. The difference between the two is the equivalent height difference. The measurement accuracy must be controlled within 0.01 meters.

[0035] The carrier wavelength of navigation satellite signals can be determined according to the frequency band of the navigation system actually used. In addition to the GPS L1 frequency band, which is preferred, if the BeiDou Navigation Satellite System (BDS) B1 frequency band is used, the carrier wavelength can be 0.192 meters; if the GLONASS system (GLONASS) G1 frequency band is used, the carrier wavelength can be 0.1602 meters. These are all publicly available standard frequency band parameters of each navigation system.

[0036] The calculation of the angle difference must ensure that the units of the satellite projection elevation angle and the current mechanical tilt angle are consistent, and both should be calculated in degrees or radians to avoid errors caused by unit confusion.

[0037] The synchronization interference prediction module generates a synchronization quality index reflecting the navigation signal locking quality based on the dominant multipath phase difference, specifically including calculation according to the following formula: In the formula, Indicates time No. The reflection amplitude ratio of each navigation satellite; This indicates the preset maximum reflection amplitude ratio; Represents an exponential function with the natural constant as its base; Indicates time No. The satellite projection elevation angle of the navigation satellite; Indicates time The current mechanical tilt angle; This indicates the preset corner window width parameter; Indicates time No. Multipath superposition power factor of navigation satellites; Indicates time No. The dominant multipath phase difference value of the navigation satellite; Represents the cosine function; Indicates time No. Predicted carrier-to-noise ratio attenuation values ​​for each navigation satellite; Represents the logarithmic function with base 10; This refers to the synchronization quality index; This indicates the total number of visible navigation satellites during the current time period; This represents the summation operation; This represents the preset exponential mapping scale constant.

[0038] The maximum reflection amplitude ratio is a preset parameter characterizing the ratio of the strongest intensity of the specular reflection signal to the direct signal intensity of a photovoltaic module. It is preferably 0.6 because this value covers the specular reflection intensity range of most commercial photovoltaic modules due to the measured reflection characteristics of the photovoltaic module's glass surface.

[0039] The corner window width parameter is a preset parameter used to adjust the steepness of the Gaussian function, determining the sensitive range of the reflection amplitude ratio as a function of angle difference. It is preferably 0.10 radians, a value that accurately captures the effective angle range of reflection based on the tilt rate of the single-axis tracking bracket and the intraday variation characteristics of the satellite elevation angle.

[0040] The reflection amplitude ratio is calculated based on the Gaussian function and reflects the ratio of the intensity of the reflected signal to the intensity of the direct signal of the photovoltaic module at a specific angle difference.

[0041] The multipath superposition power factor is a physical quantity that combines the superposition effect of direct and reflected signals, characterizing the degree of influence of multipath interference on the received signal power.

[0042] The predicted carrier-to-noise ratio (CNR) attenuation is a quantitative value that reflects the degree of decrease in the CNR of the navigation signal after converting the multipath superposition power factor to the logarithmic domain.

[0043] Synchronization quality index is a comprehensive index reflecting the overall navigation signal locking quality, obtained by exponentially averaging the predicted carrier-to-noise ratio attenuation values ​​of all visible navigation satellites.

[0044] The application logic of the Gaussian function is based on the specular reflection characteristics of photovoltaic modules. The reflection amplitude ratio decreases as the angular difference between the satellite projection elevation angle and the mechanical tilt angle increases, which conforms to the law in actual engineering that the smaller the angular difference, the stronger the reflection. For example, when the angular difference is 0, the reflection amplitude ratio is close to the maximum reflection amplitude ratio of 0.6; when the angular difference increases to 0.3 radians, the reflection amplitude ratio decreases to below 0.1, which can accurately simulate the change in reflection intensity under different angular relationships.

[0045] The formula for calculating the multipath superposition power factor is derived from the principle of coherent superposition of electromagnetic waves. 1 represents the normalized power of the direct signal, the square of the reflection amplitude ratio represents the normalized power of the reflected signal, and the product of twice the reflection amplitude ratio and the cosine of the phase difference represents the interference term of the two signals. The sum of the three can completely characterize the total power after multipath superposition.

[0046] The exponential averaging calculation is designed to reduce the impact of abnormal carrier-to-noise ratio attenuation of a single satellite on the overall assessment. By fusing data from multiple satellites, the synchronization quality index is made more stable, which is in line with the characteristics of multi-satellite collaborative operation in navigation systems.

[0047] The Gaussian function is in the form of a standard normal Gaussian function. When calculating it, you can directly substitute the square of the angle difference, the square of the corner window width parameter, and the maximum reflection amplitude ratio.

[0048] The specific calculation method for converting the predicted carrier-to-noise ratio (CNR) attenuation value into the logarithmic domain is to multiply 10 by the logarithm of the multipath superposition power factor with base 10. This conversion method is the standard method for calculating the CNR in the field of communications.

[0049] The specific steps of the exponential averaging operation are as follows: First, calculate the arithmetic mean of the predicted carrier-to-noise ratio attenuation values ​​of all visible navigation satellites. Then, divide this average by the exponential mapping scale constant. Finally, perform a natural exponential operation on the result. The preferred exponential mapping scale constant is 6, which balances the sensitivity and stability of the index. The selection criterion for visible navigation satellites is that the satellite projection elevation angle is not less than 5 degrees. This criterion can eliminate weak signal satellites near the horizon, avoiding the impact of low-quality satellite data on the accuracy of the synchronization quality index.

[0050] The exponential mapping scale constant is a preset parameter used to adjust the numerical range of synchronization quality indicators, preferably 6, to meet the common variation range of carrier-to-noise ratio attenuation prediction values.

[0051] The transmission parameter configuration module establishes a mapping relationship between the synchronization quality index and the uplink transmission capacity to generate a transmission availability coefficient, specifically including calculation according to the following formula: In the formula, Indicates time The standard deviation of the timing advance error; This indicates the preset timing advance reference error parameter; This indicates the preset timing advance degradation amplification factor; Indicates time The aforementioned synchronization quality indicators; Indicates time The standard deviation of Doppler residual frequency offset error; This represents the preset Doppler frequency offset reference error parameter; This indicates the preset frequency offset degradation amplification factor; This indicates the feasibility of synchronization. Represents the natural exponential function; This indicates the preset frequency offset tolerance scale; This indicates the preset timing advance tolerance scale; This represents the signal-to-noise ratio (SNR) feasibility metric. Indicates time The measured signal-to-noise ratio; and This represents the predefined shape parameters of the logical stith function; This represents the transmission availability coefficient.

[0052] The timing lead reference error parameter is a preset reference error value for timing lead pre-compensation when the global navigation satellite system is operating normally. It is preferably 2×10-1. -4 Seconds represent the typical reference error range for timing advance in satellite narrowband communication systems.

[0053] The Doppler frequency offset reference error parameter is a preset reference error value for Doppler frequency offset pre-compensation when the global navigation satellite system is operating normally. It is preferably 5 Hz, representing a common fluctuation range of Doppler frequency offset in navigation satellite signals, and meets the engineering requirements of most narrowband satellite communication scenarios.

[0054] The degradation amplification factor is a preset parameter used to amplify the influence of synchronization quality indicators on pre-compensation errors. It is preferably 10, based on the common numerical range of synchronization quality indicators, which allows the error to exhibit a reasonable non-linear change as synchronization quality degrades.

[0055] The standard deviation of timing advance error is a statistic that reflects the dispersion of the current timing advance pre-compensation error. It is calculated by coupling the baseline error and the synchronization quality index.

[0056] The standard deviation of Doppler residual frequency offset error is a statistic that reflects the dispersion of the current Doppler frequency offset pre-compensation residual error. It is also calculated by coupling the benchmark error and the synchronization quality index.

[0057] The timing advance tolerance scale is a preset upper limit for acceptable timing advance errors in a satellite narrowband communication system. It is preferably 1×10-1. -3 The timing synchronization requirement for satellite narrowband random access is met within seconds, ensuring that errors do not affect the access success rate.

[0058] The frequency offset tolerance scale is a preset upper limit for the acceptable Doppler residual frequency offset error of a satellite narrowband communication system. It is preferably 50 Hz, based on the subcarrier spacing characteristics of satellite narrowband communication, to avoid inter-carrier interference caused by frequency offset.

[0059] The synchronization feasibility index is a parameter that reflects the feasibility of transmission based on the synchronization status of the Global Navigation Satellite System, and its value ranges from 0 to 1.

[0060] The measured signal-to-noise ratio (SNR) of the current uplink is the power ratio of the uplink signal to the noise, measured in real time by the satellite narrowband terminal. It can be acquired through the baseband signal processing module of the satellite narrowband terminal or read from the terminal's link quality monitoring interface.

[0061] The signal-to-noise ratio (SNR) feasibility metric converts the measured SNR into a value between 0 and 1, reflecting the feasibility of link transmission quality.

[0062] The transmission availability coefficient is the product of the synchronization feasibility index and the signal-to-noise ratio feasibility index. It is a core parameter that comprehensively reflects the synchronization status and link quality, and its value ranges from 0 to 1.

[0063] A mapping relationship between synchronization quality indicators and pre-compensation errors is established, using the calculation logic of 1 plus a degradation amplification factor divided by the synchronization quality indicator. This is because as the synchronization quality indicator decreases, the pre-compensation error exhibits a non-linear growth, and this formula can accurately simulate the engineering characteristics. For example, when the synchronization quality indicator decreases from 1 to 0.1, the standard deviation of the timing advance error decreases from 2 × 10⁻⁶. -4 Increased to 2.2 × 10 seconds -3 The time interval is consistent with the actual pattern that multipath interference leads to a deterioration in synchronization accuracy.

[0064] The synchronization feasibility index is calculated using an exponential function because when the error standard deviation exceeds the tolerance scale, the probability of synchronization failure will rise sharply. The exponential function can quickly lower the feasibility, which is consistent with the threshold characteristics of communication systems.

[0065] The logistic function is used to process the measured signal-to-noise ratio because there is a critical value for the signal-to-noise ratio. Below this value, the link quality deteriorates sharply, while above this value, the link quality tends to stabilize. The S-shaped curve of the logistic function can accurately fit this change, mapping the signal-to-noise ratio to a continuous feasibility from 0 to 1.

[0066] The transmission availability coefficient is obtained by multiplying the synchronization feasibility and the signal-to-noise ratio feasibility because the successful transmission of satellite narrowband communication depends on both the synchronization accuracy of the global navigation satellite system and the link quality. Both are indispensable, and the product can comprehensively reflect the synergistic effect of the two.

[0067] The specific parameters of the logistic function are set as follows: the shape parameter θ is preferably 0 dB, and the shape parameter κ is preferably 2. The values ​​are based on the fact that the common range of signal-to-noise ratio for satellite narrowband communication links is -10 dB to 20 dB. This combination of parameters can make the signal-to-noise ratio feasibility transition smoothly in the critical region.

[0068] When calculating the standard deviation of timing lead error and the standard deviation of Doppler residual frequency offset error, it is necessary to ensure that all parameters are in the same unit. Timing lead related parameters should be uniformly expressed in seconds, and frequency offset related parameters should be uniformly expressed in Hertz to avoid unit confusion that could lead to calculation errors.

[0069] The values ​​of timing lead tolerance and frequency offset tolerance can be adjusted according to the specific satellite narrowband communication system. If the system uses a smaller subcarrier spacing, the frequency offset tolerance can be set to 20 Hz; if the system requires higher timing accuracy, the timing lead tolerance can be set to 5 × 10⁻⁶ Hz. -4 Second.

[0070] Before calculating the natural exponent, it is necessary to ensure that the sum of the two squares is non-negative, since both the error standard deviation and the tolerance scale are positive, and the sum of squares must be non-negative.

[0071] The sampling frequency of the measured signal-to-noise ratio must be consistent with the system transmission cycle, that is, once every 60 seconds, to ensure that it matches the time dimension of the synchronization quality index, so that the transmission availability coefficient can reflect the current transmission status in real time.

[0072] The transmission parameter configuration module sets the net payload byte quota and error correction coding redundancy for the current transmission cycle based on the transmission availability coefficient, specifically including calculations according to the following formula: In the formula, Indicates time The redundancy of the error correction coding; This indicates the preset lower limit parameter for the redundancy ratio; This indicates the preset upper limit parameter for the redundancy ratio; Indicates time The transmission availability coefficient; Indicates the basic available byte length; This indicates the operation of finding the maximum value. This indicates the preset maximum transmission unit length for a single uplink; Indicates the preset fixed frame header length; This indicates the total number of preset data categories; Indicates the preset single-segment data overhead length; Represents the value of zero; Indicates time The current available byte length; Indicates time The net payload byte quota.

[0073] The redundancy ratio lower limit parameter is the minimum value of the preset error correction coding redundancy. It is preferably 0.05, which meets the basic error correction requirements of satellite narrowband communication. This value can reduce redundancy overhead and improve transmission efficiency when transmission conditions are good.

[0074] The upper limit parameter for redundancy ratio is the maximum value of the preset error correction coding redundancy. A value of 0.35 is preferred to meet the error correction requirements of weak signal windows in photovoltaic power plants. This value provides sufficient redundancy to ensure data integrity when multipath interference is strong.

[0075] Error correction coding redundancy is a parameter that reflects the strength of data error correction and verification, and is dynamically adjusted by the transmission availability coefficient.

[0076] The maximum transmission unit length for a single uplink is the preset maximum data length that a satellite narrowband terminal can transmit in a single uplink. It is preferably 256 bytes, which meets the protocol specifications of satellite narrowband communication and complies with the transmission capacity limitations of most IoT terminals.

[0077] The fixed frame header length is the total number of bytes of fixed fields in the preset adaptive data frame. A length of 40 bytes is preferred, which satisfies the storage requirements of the core parameters (mechanical tilt angle, synchronization quality indicators, etc.) that the frame header must contain, fully carrying critical information without consuming excessive transmission resources.

[0078] The total number of data categories is the preset number of categories for photovoltaic power plant operation and monitoring data. Six categories are preferred to meet the core data types of photovoltaic power plant operation and maintenance (alarms, status, power, etc.) and comprehensively cover key operation and maintenance needs.

[0079] The single-segment data overhead length is a preset fixed number of overhead bytes for each type of data segment. A length of 6 bytes is preferred to meet the basic overhead requirements for data segment type identification, length field, CRC checksum, etc., and conforms to the general standard of TLV encoding.

[0080] The basic available byte length is the basic space available for data payload and redundancy checks after deducting the fixed frame header and fixed overhead of all data segments.

[0081] The current available byte length is the total number of bytes that can actually be allocated in the current transmission cycle after scaling the base available byte length according to the transmission availability coefficient.

[0082] The payload byte quota is the total number of bytes available for storing valid data during the current transmission cycle.

[0083] The core logic of establishing a negative correlation between error correction coding redundancy and transmission availability coefficient is that a lower transmission availability coefficient indicates poorer synchronization or link quality, leading to a higher risk of data transmission failure, thus requiring increased error correction redundancy to resist interference. For example, when the transmission availability coefficient is 0.9 (good transmission conditions), the error correction coding redundancy is 0.05 + (0.35 - 0.05) × (1 - 0.9) = 0.08, with relatively low redundancy overhead; when the transmission availability coefficient is 0.2 (poor transmission conditions), the error correction coding redundancy is 0.05 + 0.3 × 0.8 = 0.29, significantly increasing redundancy overhead and effectively correcting transmission errors.

[0084] The calculation logic for the basic available byte length is to accurately strip away the fixed transmission overhead, ensuring that all subsequent allocated bytes are used for valid data and error correction verification, thus avoiding fixed overhead occupying critical transmission resources.

[0085] The payload byte quota is obtained by dividing the current available byte length by (1 + error correction coding redundancy), which realizes a closed-loop allocation of payload and redundancy, ensuring that the total number of bytes does not exceed the current available space, while taking into account the effective data volume and error correction capability.

[0086] The maximum transmission unit length for a single uplink can be adjusted according to the actual satellite narrowband communication protocol used. If the NB-IoT protocol is used, a value of 256 bytes is preferred; if the LoRa protocol is used, a value of 512 bytes can be used, both of which conform to the maximum transmission unit specifications of the corresponding protocols.

[0087] The fixed frame header of 40 bytes consists of core fields such as a magic number (2 bytes), a version number (1 byte), a data segment number (1 byte), a timestamp (4 bytes), a mechanical tilt angle (4 bytes), and a synchronization quality index (4 bytes). The field lengths are reasonably allocated.

[0088] The 6-byte overhead for a single data segment consists of: 1 byte for type identifier, 2 bytes for data length, 2 bytes for checksum, and 1 byte for reserved fields. This design conforms to the general overhead design for IoT data transmission, ensuring the integrity and identifiability of data segments.

[0089] The data is categorized into six types: alarm protection data, inverter status data, power and energy data, meteorological data, metering data, and heartbeat maintenance data, covering the core scenarios of photovoltaic power plant operation and maintenance. The classification logic conforms to industry practice.

[0090] When calculating the basic available byte length, if the product of the maximum transmission unit length for a single uplink subtracted from the fixed frame header and the total number of data categories and the single segment data overhead length is negative, it is directly taken as 0.

[0091] The adaptive framing module calculates the transmission priority of the site operation monitoring data based on the transmission availability coefficient, specifically including the calculation according to the following formula: In the formula, Indicates time No. The semantic urgency of the station operation monitoring data described above; Indicates the preset first The basic importance parameters of class data; Represents the natural exponential function; Indicates the preset first The time decay rate of data; Indicates time No. The current data storage age of the data type; Indicates time No. The transmission priority of class data; Indicates the preset first Priority enhancement coefficient for class data; This represents the value one; Indicates time The transmission availability coefficient.

[0092] Data storage age is the duration during which a certain type of station operation monitoring data has not been transmitted from its generation or last update to the current time.

[0093] The basic importance parameter is a preset weight value that characterizes the inherent importance of various types of station operation monitoring data. Priority values ​​are assigned according to data category: alarm protection data 1.0, inverter status data 0.7, power energy data 0.5, meteorological data 0.45, metering data 0.4, and heartbeat maintenance data 0.2, which aligns with the operation and maintenance priorities of photovoltaic stations and ensures that critical operation and maintenance data receives higher weight.

[0094] The timeliness decay rate is a preset coefficient that characterizes how quickly the semantic urgency of various data types decays with storage age. Preferred values ​​are categorized by data type: alarm protection data 1 / 120 per second, inverter status data 1 / 300 per second, power and energy data 1 / 600 per second, meteorological data 1 / 600 per second, metering data 1 / 900 per second, and heartbeat maintenance data 1 / 1800 per second. The value is determined by the timeliness requirements of the data; alarm data decays the fastest, while maintenance data decays the slowest.

[0095] Semantic urgency is a quantitative indicator that combines the fundamental importance of data with its storage age, reflecting the current semantic value of the data.

[0096] The priority enhancement coefficient is a preset parameter used to enhance the priority of critical data when transmission conditions deteriorate. Priority values ​​are divided by data category: alarm protection data 3.0, inverter status data 2.0, power energy data 1.2, meteorological data 1.0, metering data 0.8, and heartbeat maintenance data 0.5. The values ​​are based on the maintenance priority of the data in harsh transmission environments.

[0097] Transmission priority is a quantitative indicator that combines semantic urgency and transmission availability coefficient, reflecting the current transmission priority level of data.

[0098] The semantic urgency is calculated by combining the fundamental importance of data with its time-related decay. The core logic is that the actual value of data depends on its inherent importance and decreases with storage time, which aligns with the practical need in photovoltaic power plant operation and maintenance to prioritize the value of important and recent data. For example, in the initial stage of alarm protection data generation, the semantic urgency is 1.0 × exp(-(1 / 120) × 0) = 1.0, with the highest priority; if it is stored for 300 seconds without being sent, the semantic urgency drops to 1.0 × exp(-(1 / 120) × 300) ≈ 0.08, and its value significantly decreases.

[0099] The introduction of a transmission availability coefficient to enhance priority is because a lower transmission availability coefficient indicates a greater scarcity of transmission resources, necessitating priority for high-value data transmission. This is achieved through an exponential calculation of (1 - transmission availability coefficient) × priority enhancement coefficient, resulting in a non-linear enhancement of critical data priority. For example, when the transmission availability coefficient is 0.3, the priority enhancement factor for alarm protection data is exp(3.0 × (1 - 0.3)) ≈ 8.17, while that for heartbeat maintenance data is only exp(0.5 × 0.7) ≈ 1.41, significantly amplifying the priority of critical data.

[0100] The data storage age is updated every 60 seconds (transmission cycle). If new data is written to this type of data in the current cycle, the age is reset to 0; if no new data is written, the age is increased by 60 seconds based on the previous cycle, with a maximum age of 86400 seconds to avoid old data occupying resources for a long time. The six categories of station operation monitoring data are specifically divided as follows: alarm protection data (tripping, islanding, overvoltage, overtemperature, etc.), inverter status data (start / stop status, power limit indicator, fault code, etc.), power and energy data (active power, reactive power, power generation, etc.), meteorological data (irradiance, ambient temperature, wind speed, etc.), metering data (grid connection point voltage, current, frequency, etc.), and heartbeat maintenance data (equipment health status, software version, remaining power, etc.).

[0101] The values ​​of the basic importance parameter, the time-related decay rate, and the priority enhancement coefficient must correspond one-to-one with the above six types of data. They should be written into the system configuration file during configuration and can be fine-tuned according to the site operation and maintenance needs. The adjustment range should not exceed ±0.2 to ensure the stability of the priority sorting logic.

[0102] Natural exponent operations must be implemented using a standard math library, and six decimal places must be retained during calculation to avoid insufficient numerical precision leading to abnormal priority ordering.

[0103] The adaptive framing module sorts the station operation monitoring data according to the transmission priority, extracts data segments based on the payload byte quota, and assembles a reordered data frame containing a variable-length data payload and a variable-length redundancy check code by combining the error correction coding redundancy. Specifically, it includes calculations according to the following formula: In the formula, Indicates time No. Assign weights to class data; Indicates time No. The transmission priority of class data; This represents the maximum priority across all categories. This represents the summation operation; Indicates the total number of data categories; Indicates time No. The theoretical number of bytes allocated for this type of data; Indicates time The net payload byte quota; Indicates the first The allocated byte length for class data; This indicates the floor function; Indicates the first Error correction and verification byte length for class data; Indicates time The redundancy of the error correction coding; Indicates the global scaling factor; Indicates time The current available byte length; Represents a very small positive constant; This indicates an assignment / update operation; This refers to the reordered data frame; Indicates a fixed frame header; This indicates a data concatenation operation; This indicates the number of transmissions arranged in descending order of transmission priority. Indexes for each data class; This indicates the length is after adjustment. Data fragments; This indicates the length is after adjustment. Error correction check code; Indicates a filled segment.

[0104] The data allocation weight is calculated based on the transmission priority using an exponential normalization function. It is a calculation parameter that characterizes the proportion of net payload bytes that can be allocated to each type of station operation monitoring data.

[0105] The theoretical allocated bytes are obtained by multiplying the net payload byte quota by the corresponding data allocation weight. This is the calculation parameter for the theoretically allocable net payload bytes for each type of data.

[0106] The allocated byte length is a calculation parameter for the initial net payload byte allocation length of each type of data, obtained by rounding down the theoretical allocated byte amount.

[0107] The error correction check byte length is obtained by multiplying the error correction coding redundancy by the theoretical allocated byte size and then rounding down. It is the calculation parameter for the initial error correction check byte length of each type of data.

[0108] The global scaling factor is the ratio of the currently available byte length to the sum of the initial allocated byte lengths and error correction / checking byte lengths for all categories. It is used to uniformly adjust the calculation parameters for the byte lengths of various data types.

[0109] The adjusted allocation byte length is obtained by multiplying the global scaling factor by the initial allocation byte length and then rounding down. This is the calculation parameter for the final net payload byte allocation length for each type of data.

[0110] The adjusted error correction check byte length is obtained by multiplying the global scaling factor by the initial error correction check byte length and then rounding down. This is the calculation parameter for the final error correction check byte length of each data type.

[0111] The maximum value of all priority categories is obtained by taking the maximum value of the transmission priority of the operation monitoring data of various types of stations, and is used as a reference parameter for the calculation of index normalization.

[0112] The data class index sequence is generated by sorting various types of data according to their transmission priority from high to low, and it represents the index sequence calculation parameters that characterize the data framing order.

[0113] A reordered data frame is composed of a fixed frame header, variable-length data segments arranged in an index sequence, variable-length error correction check codes, and padding segments.

[0114] The padding segment is a byte segment calculation parameter used to complete the frame length when the total number of bytes of data fragments and checksums is less than the currently available byte length.

[0115] The exponential normalization function is used to calculate data weight allocation. It stabilizes the values ​​by subtracting the maximum value of all category priorities, preventing exponential overflow caused by excessively large priority values. Simultaneously, it assigns higher weights to high-priority data while compressing the weights of lower-priority data. For example, if three data categories have priorities of 6, 4, and 2, with a maximum value of 6, after exponential normalization, the highest-priority data will account for over 80% of the weight, thus allocating resources to core data.

[0116] The design of the global scaling factor realizes the closed-loop constraint of transmission resources. When the total initial byte length of various types of data exceeds the current available byte length, the scaling factor is used to ensure that the total number of bytes matches the current available space and avoids transmission failure caused by frame length exceeding the limit.

[0117] Data segments are extracted from the head of the data queue according to the data category index sequence, following the first-in-first-out principle to ensure that the earliest generated high-priority data is transmitted first, meeting the timeliness requirements of photovoltaic power station operation and maintenance data and avoiding the backlog of old core data.

[0118] The current mechanical tilt angle, synchronization quality index, and transmission availability coefficient are incorporated into the fixed frame header, allowing the receiver to directly determine the transmission status based on these parameters.

[0119] The combination of variable-length data payload and variable-length error correction code design allows the transmission resources of each type of data to be adapted to both its own priority and the current channel conditions. High-priority data is allocated more payload bytes and is also matched with corresponding error correction capabilities.

[0120] The exponential normalization function uses a stable soft maximization function, which is specifically calculated as the natural exponent of each data category after subtracting the maximum value, divided by the sum of the natural exponents of that value across all categories.

[0121] All rounding operations uniformly adopt the round-down rule, and all byte length calculation results are taken as the largest integer not greater than the value, ensuring that the byte length is a positive integer and meets the byte unit requirements for data transmission.

[0122] The minimum positive constant in the global scaling factor calculation is preferably 1×10⁻⁶. -12 This is used to prevent the denominator from being zero; the value is small enough that it will not affect the calculation accuracy.

[0123] The error correction check code adopts Lisolomon coding, which is suitable for the channel characteristics of satellite narrowband communication, can effectively correct random and burst errors in the transmission process, and is adapted to the complex electromagnetic environment of photovoltaic power plants.

[0124] The data queue adopts a first-in-first-out storage rule, with each type of data forming an independent queue. The maximum queue length is set to 1024 bytes to avoid long-term data backlog that occupies storage resources.

[0125] The 40-byte fixed frame header is specifically composed of 4 bytes of mechanical tilt angle, 8 bytes of synchronization quality index, 4 bytes of transmission availability coefficient, 4 bytes of timestamp, 1 byte of data segment number, and 19 bytes of reserved space.

[0126] The padding segment uses 0-value bytes for padding, and the padding length is the current available byte length minus the total number of bytes of data fragments and checksums, ensuring that the frame length meets the frame structure requirements of satellite narrowband communication.

[0127] like Figure 2 As shown, Figure 2The demonstration showcased the satellite communication signal propagation scenario of a single-axis tracking photovoltaic power station, illustrating the signal transmission relationship between the navigation satellite and the communication receiving antenna: the single-axis tracking bracket supports the photovoltaic modules, and the modules can adjust their mechanical tilt angle with the bracket. The signal emitted by the navigation satellite is divided into two paths: one is a direct signal that reaches the communication receiving antenna directly, and the other is a reflected signal that reaches the antenna after being reflected by the mirror surface of the photovoltaic module.

[0128] It should be noted that the interval and threshold sizes are set for ease of comparison. The size of the threshold depends on the amount of sample data and the base number set by those skilled in the art for each set of sample data, as long as it does not affect the proportional relationship between the parameter and the quantized value. Furthermore, the above formulas are all dimensionless calculations, and the formulas are derived from software simulations using a large amount of collected data to obtain the most recent real-world results. The preset parameters in the formulas are set by those skilled in the art according to the actual situation.

[0129] The embodiments of this example have been described above. However, this example is not limited to the specific implementation methods described above. The specific implementation methods described above are merely illustrative and not restrictive. Those skilled in the art can make many other forms based on the guidance of this example, and all of them are within the protection scope of this example.

Claims

1. A photovoltaic power station operation adaptive transmission system based on satellite narrowband communication, characterized in that, include: The status perception module is used to collect the current mechanical tilt angle and mechanical tilt angle change rate of the single-axis tracking bracket of the photovoltaic power station in real time, obtain the satellite ephemeris data of the visible navigation satellites in the current period, and receive the station operation monitoring data to be sent. The synchronization interference prediction module is used to calculate the satellite projection elevation angle based on the current mechanical tilt angle and the satellite ephemeris data, calculate the dominant multipath phase difference of the navigation satellite signal in combination with the specular reflection characteristics of the photovoltaic module reflector, and generate a synchronization quality index reflecting the locking quality of the navigation signal based on the dominant multipath phase difference. The transmission parameter configuration module is used to establish the mapping relationship between the synchronization quality index and the uplink transmission capacity to generate the transmission availability coefficient, and to set the net payload byte quota and error correction coding redundancy of the current transmission cycle based on the transmission availability coefficient. An adaptive framing module is used to calculate the transmission priority of the site operation monitoring data based on the transmission availability coefficient, sort the site operation monitoring data according to the transmission priority, extract data segments based on the payload byte quota, and assemble a reordered data frame containing variable-length data payload and variable-length redundancy check code by combining the error correction coding redundancy.

2. The photovoltaic power station operation adaptive transmission system based on satellite narrowband communication according to claim 1, characterized in that, Calculating the satellite projection elevation angle based on the current mechanical tilt angle and the satellite ephemeris data includes: The satellite ephemeris data is converted into a satellite line-of-sight vector in a station-centric coordinate system with the photovoltaic power station as the origin. Extract the horizontal and vertical components of the satellite line-of-sight vector in a plane perpendicular to the tracking axis of the single-axis tracking bracket of the photovoltaic power station; The absolute values ​​of the vertical component and the horizontal component are subjected to arctangent calculation, and the resulting angle value is used as the satellite projection elevation angle to eliminate the interference of the azimuth angle in the satellite ephemeris data on the single-axis tracking reflection geometry.

3. The photovoltaic power station operation adaptive transmission system based on satellite narrowband communication according to claim 2, characterized in that, The dominant multipath phase difference of navigation satellite signals is calculated by combining the specular reflection characteristics of the photovoltaic module's reflective surface, including: Obtain the equivalent height difference between the phase center of the navigation satellite receiving antenna and the dominant reflective surface of the photovoltaic module, as well as the carrier wavelength of the navigation satellite signal; Calculate the angle difference between the satellite projection elevation angle and the current mechanical tilt angle, and perform a sine calculation on the angle difference; The result of the sine calculation is multiplied by the product of the equivalent height difference and four times the value of pi, and the resulting product is divided by the carrier wavelength to obtain the dominant multipath phase difference value.

4. The photovoltaic power station operation adaptive transmission system based on satellite narrowband communication according to claim 3, characterized in that, Based on the dominant multipath phase difference, a synchronization quality index reflecting the navigation signal locking quality is generated, including: Set the maximum reflection amplitude ratio and corner window width parameters; Calculate the square of the difference between the satellite projection elevation angle and the current mechanical tilt angle, and calculate the reflection amplitude ratio using a Gaussian function based on the square value, the corner window width parameter, and the maximum reflection amplitude ratio; Calculate the cosine value of the dominant multipath phase difference, and sum the square of the reflection amplitude ratio, the first value, and twice the product of the reflection amplitude ratio and the cosine value to obtain the multipath superposition power factor. The multipath superposition power factor is converted into a predicted carrier-to-noise ratio attenuation value in the logarithmic domain; The synchronization quality index is obtained by performing an exponential average of the predicted carrier-to-noise ratio attenuation values ​​of all visible navigation satellites in the current time period.

5. The photovoltaic power station operation adaptive transmission system based on satellite narrowband communication according to claim 4, characterized in that, Establishing a mapping relationship between the synchronization quality index and uplink transmission capacity to generate a transmission availability coefficient includes: Set the timing advance reference error parameter, Doppler frequency offset reference error parameter, and degradation amplification factor; The sum of the calculated value and the quotient of the degradation amplification factor divided by the synchronization quality index is multiplied by the timing advance reference error parameter and the Doppler frequency offset reference error parameter respectively to obtain the standard deviation of timing advance error and the standard deviation of Doppler residual frequency offset error. Set a timing advance tolerance scale and a frequency offset tolerance scale, and calculate the square of the ratio of the standard deviation of the timing advance error to the timing advance tolerance scale, and the square of the ratio of the standard deviation of the Doppler residual frequency offset error to the frequency offset tolerance scale. The natural exponent is then applied to the negative sum of the two squared values ​​to obtain the synchronization feasibility index. Obtain the measured signal-to-noise ratio (SNR) of the current uplink and use the logistic function to calculate the SNR feasibility index corresponding to the measured SNR. The transmission availability coefficient is obtained by multiplying the synchronization feasibility index by the signal-to-noise ratio feasibility index.

6. The photovoltaic power station operation adaptive transmission system based on satellite narrowband communication according to claim 5, characterized in that, Based on the transmission availability coefficient, the net payload byte quota and error correction coding redundancy for the current transmission cycle are set, including: Set a lower limit parameter and an upper limit parameter for the redundancy ratio, calculate the difference between the value one and the transmission availability coefficient, multiply the difference between the upper limit parameter and the lower limit parameter for the redundancy ratio, and add the product to the lower limit parameter for the redundancy ratio to obtain the error correction coding redundancy. Obtain the maximum transmission unit length for a single uplink, the fixed frame header length, the total number of data categories, and the single segment data overhead length. Calculate the value obtained by subtracting the fixed frame header length, the total number of data categories, and the single segment data overhead length from the maximum transmission unit length for a single uplink and compare this value with zero to obtain the larger value, thus obtaining the basic available byte length. Multiply the base available byte length by the transmission availability coefficient to obtain the current available byte length; The net payload byte quota is obtained by calculating the quotient of the current available byte length divided by the sum of the numerical value and the error correction coding redundancy.

7. The photovoltaic power station operation adaptive transmission system based on satellite narrowband communication according to claim 6, characterized in that, Calculating the transmission priority of the site operation monitoring data based on the transmission availability coefficient includes: For each type of data in the station operation monitoring data, obtain the data storage age at the current moment; Set a basic importance parameter and a time-related decay rate, calculate the negative value of the product of the time-related decay rate and the data storage age, perform natural exponentiation on the negative value, and multiply the result by the basic importance parameter to obtain the semantic urgency. Set a priority enhancement coefficient, calculate the difference between the numerical value and the transmission availability coefficient, multiply the difference by the priority enhancement coefficient and perform a natural exponential operation, and multiply the result by the semantic urgency to obtain the transmission priority.

8. The photovoltaic power station operation adaptive transmission system based on satellite narrowband communication according to claim 7, characterized in that, The station operation monitoring data is sorted according to the transmission priority, and data segments are extracted based on the payload byte quota. These segments are then assembled with the error correction coding redundancy to generate a reordered data frame containing a variable-length data payload and a variable-length redundancy check code, including: Based on the transmission priority, the data allocation weight of each type of station operation monitoring data is calculated using the exponential normalization function. The net payload byte quota is multiplied by the data allocation weight and rounded to obtain the allocated byte length of each type of station operation monitoring data. The error correction verification byte length for each type of station operation monitoring data is obtained by multiplying the error correction coding redundancy by the allocated byte length and rounding down. Calculate the ratio of the current available byte length to the sum of the allocated byte length and the error correction and verification byte length for all categories to obtain a global scaling factor. Use the global scaling factor to adjust the allocated byte length and the error correction and verification byte length for each category of the station operation monitoring data. The station operation monitoring data of all categories are sorted in descending order of transmission priority to generate a data category index sequence; A fixed frame header is constructed, which includes the current mechanical tilt angle, the synchronization quality index, and the transmission availability coefficient. According to the data class index sequence, data segments with a length equal to the adjusted allocated byte length are extracted from the head of the data queue of each type of station operation monitoring data. An error correction check code with a length equal to the adjusted error correction check byte length is generated. The data segments and the error correction check code are then concatenated to the fixed frame header to form the reordered data frame.

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