A distributed photovoltaic grid-connected detection method

Abstract

The present invention discloses a distributed photovoltaic grid-connected detection method, comprising the following steps: S1, control chip self-test; S2, obtaining a square wave signal from the distributed photovoltaic power grid; S3, obtaining power quality technical parameters using square wave signal analysis, analyzing and statistically analyzing the power quality technical parameters to obtain power quality detection results; S4, estimating the amount of light radiation received by the photovoltaic cells; S5, collecting the actual temperature of the photovoltaic cells, obtaining the local average relative humidity and airborne particle concentration data of the photovoltaic power station, and calculating the annual attenuation coefficient of the photovoltaic power station by inputting the operating time of the photovoltaic power station, ultimately obtaining the total amount of electricity generated by the photovoltaic cells; S6, calculating various losses in the photovoltaic power station system, ultimately obtaining the total amount of electricity generated by the photovoltaic power station connected to the grid; S7, obtaining a power generation efficiency detection result by calculating the total amount of grid-connected electricity and the total amount of solar radiation. The present invention can realize two detections of power quality and power generation efficiency of distributed photovoltaic grid-connected.

Description

Technical Field

[0001] The present invention relates to the technical field of photovoltaic grid-connected detection, and in particular to a distributed photovoltaic grid-connected detection method. Background Art

[0002] In recent years, electricity consumption for production and daily life has surged. Traditional power generation methods have struggled to meet actual electricity demand, and the generation of electricity consumes significant amounts of fossil fuels, hindering ecological conservation and alleviating resource supply and demand imbalances. Against this backdrop, photovoltaic power generation and distributed photovoltaic grid-connected technologies have garnered industry attention. Integrating distributed photovoltaic systems into distribution networks is crucial for alleviating local electricity shortages, protecting the ecological environment, and enhancing distribution network operational flexibility.

[0003] A distributed photovoltaic power generation system uses decentralized resources to disperse small-scale photovoltaic power generation systems near users, install photovoltaic modules, batteries and other facilities and equipment, and the photovoltaic modules continuously convert the absorbed solar energy into electrical energy and input it into the public power grid to provide power to nearby users.

[0004] A distributed photovoltaic power generation system consists of four components: a photovoltaic array, a controller, an inverter, and a battery pack. Relying on photovoltaic panels, this system continuously converts solar energy into electricity for user consumption and feeds excess electricity into the grid. As the capacity and scale of distributed photovoltaic power generation grid-connected increases, the flow patterns of the grid become more complex, significantly impacting the entire grid. When large-scale distributed photovoltaic power generation grids are connected, it is highly likely to cause regional node voltages to exceed their limits. Transient faults in power lines can also cause automatic reclosing to fail, posing risks to the safe and stable operation of the power grid system.

[0005] In order to reduce the adverse effects of photovoltaic grid connection on the power grid system, it is necessary to test the photovoltaic grid connection. The photovoltaic grid connection test project mainly includes power quality detection and power generation efficiency detection and evaluation. The existing technology has not yet realized the method of testing the two projects of photovoltaic grid connection. Summary of the Invention

[0006] The purpose of the present invention is to solve the technical problem of the lack of an effective detection method for distributed photovoltaic grid connection in the prior art and to provide a distributed photovoltaic grid connection detection method.

[0007] In order to solve the above-mentioned technical problems, the present invention adopts a technical solution: a distributed photovoltaic grid-connected detection method, comprising the following steps:

[0008] S1. Before the photovoltaic inverter is powered on, the correctness of the code stored in the non-volatile storage medium on the control chip is detected. If the code is correct, a power-on self-test is performed during the photovoltaic inverter startup process. If the code is incorrect, a code fault is notified.

[0009] S2. Using a signal collector to collect the line voltage waveform output by the distributed photovoltaic power grid, and converting the line voltage waveform into a sine wave signal, converting the sine wave signal into a square wave signal through zero-crossing comparison, and performing level conversion and denoising on the square wave signal;

[0010] S3. An interrupt is initiated during each rising edge of the processed square wave signal, and the grid frequency is calculated based on the number of internal pulses recorded during two consecutive interruptions. After adjusting the sampling frequency of the signal processing device to be synchronized with the grid frequency, synchronous sampling and transient data analysis are performed, and the steady-state waveform data is analyzed to obtain power quality technical parameters. The power quality technical parameters are analyzed and statistically analyzed to obtain power quality test results.

[0011] S4. Estimate the theoretical total horizontal radiation using the latitude and longitude parameters of the photovoltaic power station. Calculate the incident angle of sunlight on the photovoltaic panels using the photovoltaic array tilt angle. Further calculate the direct radiation, scattered radiation, and reflected radiation received by the photovoltaic panels. Add the three together to obtain the total solar radiation on the photovoltaic panels. Deduct the radiation received by the photovoltaic cells after shading the area, and finally obtain the total solar radiation received by the photovoltaic cells.

[0012] S5. Collect the actual temperature of the photovoltaic cells, obtain the local average relative humidity and airborne particle concentration data of the photovoltaic power station, calculate the annual attenuation coefficient of the photovoltaic power station by inputting the operating time of the photovoltaic power station, and finally obtain the total amount of electricity generated by the photovoltaic cells;

[0013] S6. Calculate various losses in the photovoltaic power station system based on the models of the inverter and transformer used in the photovoltaic power station, and ultimately obtain the total amount of grid-connected power generated by the photovoltaic power station;

[0014] S7. Obtain the power generation efficiency test result by calculating the total grid-connected power and the total solar radiation.

[0015] As a further optimization of a distributed photovoltaic grid-connected detection method of the present invention: the code verification method in step S1 is specifically: according to the binary file of the code, a cyclic redundancy check is used to calculate a check value; the judgment step is to judge whether the calculated check value is consistent with the pre-stored check value, if they are consistent, the code is determined to be correct, and if they are inconsistent, the code is determined to be incorrect.

[0016] As a further optimization of the distributed photovoltaic grid-connected detection method of the present invention: in step S2, the denoising process includes deburring and de-jittering processes.

[0017] As a further optimization of the distributed photovoltaic grid-connected detection method of the present invention: in step S4, the result is corrected using the monthly average solar radiation data.

[0018] As a further optimization of the distributed photovoltaic grid-connected detection method of the present invention: in step S5, the actual temperature of the photovoltaic cell is estimated according to the working environment temperature and working current of the photovoltaic cell.

[0019] The present invention has the following beneficial effects:

[0020] 1. The method of the present invention can perform power quality detection on distributed photovoltaic power stations, and during the detection process, it can achieve sampling frequency synchronization, which can significantly improve the accuracy of power quality detection;

[0021] 2. The method of the present invention can detect the power generation efficiency of distributed photovoltaic power stations. During the power generation efficiency detection process, the effects of lighting conditions, shading area, ambient temperature and humidity, aging of photovoltaic modules, and surface cleanliness of photovoltaic cells on power generation efficiency are fully considered, and the power generation efficiency of the photovoltaic power station can be estimated more accurately. DETAILED DESCRIPTION

[0022] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention.

[0023] A distributed photovoltaic grid-connected detection method comprises the following steps:

[0024] S1. Before the photovoltaic inverter is powered on, the correctness of the code stored in the non-volatile storage medium on the control chip is detected. If the code is correct, a power-on self-test is performed during the photovoltaic inverter startup process. If the code is incorrect, a code fault is notified.

[0025] The code verification method in step S1 is specifically as follows: according to the binary file of the code, a check value is calculated using a cyclic redundancy check; the judgment step is to judge whether the calculated check value is consistent with the pre-stored check value, if they are consistent, the code is determined to be correct, and if they are inconsistent, the code is determined to be incorrect.

[0026] S2. Use a signal collector to collect the line voltage waveform output by the distributed photovoltaic power grid, and convert the line voltage waveform into a sine wave signal. Use zero-crossing comparison to convert the sine wave signal into a square wave signal. Perform level conversion and denoising (deburring and de-jittering) on ​​the square wave signal.

[0027] S3. An interrupt is entered during each rising edge of the processed square wave signal, and the grid frequency is calculated based on the number of internal pulses recorded by two consecutive interruptions. After adjusting the sampling frequency of the signal processing device to be synchronized with the grid frequency, synchronous sampling and transient data analysis and processing are performed, and data analysis is performed on the steady-state waveform data to obtain power quality technical parameters. The power quality technical parameters are analyzed and counted to obtain power quality detection results.

[0028] S4. Estimate the theoretical total horizontal radiation using the latitude and longitude parameters of the photovoltaic power station. Calculate the incident angle of sunlight on the photovoltaic panels using the inclination angle of the photovoltaic array. Further calculate the direct radiation, scattered radiation, and reflected radiation received by the photovoltaic panels. Add the three together to obtain the total solar radiation on the photovoltaic panels. Deduct the radiation received by the photovoltaic cells after shading the area, and finally obtain the light radiation received by the photovoltaic cells.

[0029] Photovoltaic power stations all use sun tracking systems to achieve real-time adjustment of the photovoltaic array tilt angle, thereby obtaining as much solar radiation as possible. Therefore, when measuring and evaluating different photovoltaic power stations, it is necessary to determine the value of the photovoltaic array tilt angle based on the actual sun tracking system.

[0030] When the photovoltaic arrays are densely distributed, as the tilt angle of the photovoltaic arrays changes, the front array may cast a shadow on the back array, blocking some photovoltaic cells and reducing power generation. Generally, the tilt angles of adjacent photovoltaic arrays are close, so it can be assumed that the tilt angles of two adjacent photovoltaic arrays are equal.

[0031] The results were corrected using the monthly average solar radiation data.

[0032] S5. Collect the actual temperature of the photovoltaic cells (or estimate the actual temperature of the photovoltaic cells through the working environment temperature and working current of the photovoltaic cells), obtain the local average relative humidity and air suspended particle concentration data of the photovoltaic power station, calculate the annual attenuation coefficient of the photovoltaic power station by inputting the operating time of the photovoltaic power station, and finally obtain the total amount of electricity generated by the photovoltaic cells.

[0033] Rising temperatures can cause photovoltaic cells to overheat, resulting in a decrease in their photoelectric conversion efficiency. With the recent increase in extreme high-temperature weather, the impact of temperature on the efficiency of photovoltaic power plants has drawn considerable attention. High humidity can lead to haze, which reduces atmospheric transparency and reduces the amount of solar radiation received by photovoltaic panels. Therefore, when evaluating the efficiency of a photovoltaic power plant, the impact of the plant's environmental conditions must be considered.

[0034] The impact of air humidity on the power generation efficiency of photovoltaic power stations mainly includes two aspects: First, when the relative humidity is high, haze is easily generated, which leads to a decrease in atmospheric transparency, thereby reducing the solar radiation received by photovoltaic cells.

[0035] When there is a lot of dust on the surface of photovoltaic cells, its transparency is significantly reduced, which will lead to a decrease in the amount of light radiation received by the photovoltaic cells. However, the cleanliness of the surface of photovoltaic cells is related to many factors such as vegetation near the photovoltaic power station, wind speed, humidity, precipitation, air pollution indicators, etc.

[0036] S6. Calculate various losses in the photovoltaic power station system based on the models of the inverter and transformer used in the photovoltaic power station, and ultimately obtain the total amount of grid-connected power generated by the photovoltaic power station;

[0037] S7. Obtain the power generation efficiency test result by calculating the total grid-connected power and the total solar radiation.

[0038] Power generation efficiency = total amount of electric energy delivered to the grid by the photovoltaic power station within time (t) / total amount of solar radiation theoretically received by the photovoltaic cells of the photovoltaic power station within time (t) * 100%.

[0039] The power generation capacity of a photovoltaic power station is affected by factors such as lighting conditions, ambient temperature and humidity. Furthermore, the photoelectric conversion performance of photovoltaic cells declines over time. Therefore, it is necessary to calculate the power generation capacity of a photovoltaic power station and the amount of solar radiation it can receive, based on its actual operating conditions and operating conditions.

[0040] The above describes the specific embodiments of the present invention. It should be understood that the present invention is not limited to the above specific embodiments, and those skilled in the art may make various variations or modifications within the scope of the claims, which do not affect the essence of the present invention.

Claims

1. A distributed photovoltaic grid-connected detection method, characterized by: The following steps are involved: S1. Before the photovoltaic inverter is powered on, the correctness of the code stored in the non-volatile storage medium on the control chip is detected. If the code is correct, a power-on self-test is performed during the photovoltaic inverter startup process. If the code is incorrect, a code fault is notified. The code verification method specifically comprises: calculating a check value using a cyclic redundancy check based on a binary file of the code; determining whether the calculated check value is consistent with a pre-stored check value, if they are consistent, determining that the code is correct; if they are inconsistent, determining that the code is incorrect; S2. Using a signal collector to collect the line voltage waveform output by the distributed photovoltaic power grid, and converting the line voltage waveform into a sine wave signal, converting the sine wave signal into a square wave signal through zero-crossing comparison, and performing level conversion and denoising on the square wave signal; S3. An interrupt is initiated during each rising edge of the processed square wave signal, and the grid frequency is calculated based on the number of internal pulses recorded during two consecutive interruptions. After adjusting the sampling frequency of the signal processing device to be synchronized with the grid frequency, synchronous sampling and transient data analysis are performed, and the steady-state waveform data is analyzed to obtain power quality technical parameters. The power quality technical parameters are analyzed and statistically analyzed to obtain power quality test results. S4. Estimate the theoretical total horizontal radiation using the latitude and longitude parameters of the photovoltaic power station. Calculate the incident angle of sunlight on the photovoltaic panels using the photovoltaic array tilt angle. Further calculate the direct radiation, scattered radiation, and reflected radiation received by the photovoltaic panels. Add the three together to obtain the total solar radiation on the photovoltaic panels. Deduct the radiation received by the photovoltaic cells after shading the area, and finally obtain the total solar radiation received by the photovoltaic cells. S5. Collect the actual temperature of the photovoltaic cells, obtain the local average relative humidity and airborne particle concentration data of the photovoltaic power station, calculate the annual attenuation coefficient of the photovoltaic power station by inputting the operating time of the photovoltaic power station, and finally obtain the total amount of electricity generated by the photovoltaic cells; S6. Calculate various losses in the photovoltaic power station system based on the models of the inverter and transformer used in the photovoltaic power station, and ultimately obtain the total amount of grid-connected power generated by the photovoltaic power station; S7. Obtain power generation efficiency test results by calculating the total grid-connected power and the total solar radiation; Power generation efficiency = the total amount of electric energy transmitted to the grid by the photovoltaic power station in time t / the total amount of solar radiation theoretically received by the photovoltaic cells of the photovoltaic power station in time t * 100%.

2. The distributed photovoltaic grid-connected detection method according to claim 1, characterized in that: In step S2, the denoising process includes de-burring and de-jittering processes.

3. The distributed photovoltaic grid-connected detection method according to claim 1, characterized in that: In step S4, the result is corrected using the monthly average solar radiation data.

4. The distributed photovoltaic grid-connected detection method according to claim 1, wherein: In step S5, the actual temperature of the photovoltaic cell is estimated according to the working environment temperature and working current of the photovoltaic cell.