New energy power station grid-connected scheduling method

Abstract

The invention provides a grid-connected scheduling method for a new energy power station, which relates to the technical field of power system scheduling and comprises the following steps: acquiring illumination intensity and temperature of a photovoltaic power station, output voltage and current data of a photovoltaic panel and voltage, frequency and phase parameters of a power grid side; predicting the future output power of the photovoltaic power station according to the collected data; calculating and adjusting the output voltage and frequency of the photovoltaic power station according to the parameters of the power grid and the power station in combination with future output power to match with the power grid; a phase-locked loop technology is adopted to synchronize an output phase of a photovoltaic power station inverter and a power grid phase; after matching adjustment is completed, grid-connected switching is carried out by adopting a soft start technology; through an innovative grid-connected dispatching mode and an accurate mathematical model, it is ensured that the photovoltaic power station can be smoothly and efficiently connected into the power grid, meanwhile, the power quality and the power grid stability are kept, and the operation requirement of a power system is better met.

Description

Technical Field

[0001] The present invention relates to the technical field of power system dispatching, and in particular to a new energy power station grid-connected dispatching method. Background Art

[0002] With the growing global demand for clean energy and the improvement of environmental awareness, photovoltaic power generation has developed rapidly as a sustainable way of utilizing renewable energy. In recent years, photovoltaic power generation technology has continued to advance, the conversion efficiency of photovoltaic cells has gradually increased, and the cost has continued to decline. Large-scale photovoltaic power stations continue to emerge, not only playing an important role in distributed energy supply, but also occupying an increasingly large share in the field of centralized power generation; for example, in some sunny areas, photovoltaic power generation has become an important part of local power supply, and has made positive contributions to reducing dependence on traditional fossil energy; at the same time, with the development of energy storage technology, the combination of photovoltaic power generation and energy storage systems has also provided new solutions for improving energy stability and reliability, further promoting the widespread application of photovoltaic power generation in the power field;

[0003] However, the existing photovoltaic power generation prediction methods often have low prediction accuracy under complex operating conditions; inaccurate power prediction will lead to unreasonable grid dispatching plans. When the actual photovoltaic power generation deviates greatly from the predicted value, it may cause an imbalance in grid supply and demand.

[0004] At the same time, achieving phase synchronization between photovoltaic power stations and power grids is one of the key links in grid connection. However, in the process of phase synchronization, the existing technology is easily affected by grid interference and the dynamic characteristics of the photovoltaic power station itself, resulting in a complex and unstable phase synchronization process. At the moment of grid connection, if the phase difference cannot be accurately controlled within a small range, a large impact current will be generated, causing damage to the equipment of the grid and photovoltaic power station, reducing the service life of the equipment, and may even cause grid failure. For example, in some cases where the grid fluctuates greatly, the traditional phase synchronization method may not be able to adjust the inverter output phase in a timely and accurate manner, resulting in grid connection failure or unstable system operation after grid connection.

[0005] Most existing grid-connected dispatching methods lack the ability to adaptively adjust to changes in the operating status of the power grid and photovoltaic power plants. The load demand, topology structure of the power grid, and the performance of the photovoltaic power plant itself may change over time, but traditional technologies are difficult to optimize the grid-connected dispatching strategy in real time according to these changes. This makes it impossible for photovoltaic power plants to always maintain the optimal grid-connected operating state during long-term operation, affecting the economy and reliability of the entire power system.

[0006] Therefore, there is an urgent need in the art for a new energy power station grid-connected scheduling method to solve the above-mentioned problems. Summary of the invention

[0007] The present invention provides a new energy power station grid-connected scheduling method, aiming to solve the problems existing in the above-mentioned prior art. Through an innovative grid-connected scheduling method and an accurate mathematical model, it ensures that the photovoltaic power station can be smoothly and efficiently connected to the power grid, while maintaining the power quality and grid stability, and better adapting to the operation requirements of the power system.

[0008] The present invention provides a new energy power station grid-connected scheduling method, comprising:

[0009] Step 1: Collect the light intensity, temperature, photovoltaic panel output voltage and current data of the photovoltaic power station and the voltage, frequency and phase parameters of the grid side;

[0010] Step 2: predict the future output power of the photovoltaic power station based on the collected data;

[0011] Step 3: Calculate and adjust the output voltage and frequency of the photovoltaic power station based on the grid and power station parameters and the future output power to match the grid;

[0012] Step 4: Use phase-locked loop technology to synchronize the output phase of the photovoltaic power station inverter with the grid phase;

[0013] Step 5: After completing the matching adjustment, use the soft start technology to switch to the grid.

[0014] According to a new energy power station grid-connected scheduling method provided by the present invention, in step 1, the process of collecting data includes:

[0015] By arranging high-precision light sensors and temperature sensors at different locations in the power station to obtain light intensity and temperature data, installing voltage and current transformers at the junction box and inverter of the photovoltaic array to obtain photovoltaic output voltage and current data, and directly obtaining grid-side voltage, frequency, and phase parameters from the grid monitoring equipment.

[0016] According to a new energy power station grid-connected scheduling method provided by the present invention, in step 2, the process of predicting the future output power of the photovoltaic power station includes:

[0017] The photovoltaic cell output current I is calculated using a current simulation model, and the current simulation model is:

[0018]

[0019] Where I is the photovoltaic cell output current obtained through model simulation; I ph is the photocurrent, I0 is the reverse saturation current, q is the electron charge, V is the current output voltage of the photovoltaic cell, R s is the series resistance, R sh is the parallel resistance, n is the diode characteristic factor, k is the Boltzmann constant, and T is the photovoltaic cell temperature;

[0020] The photocurrent I ph =K I G; K I is the proportionality coefficient, which depends on the material and structural characteristics of the photovoltaic cell, and G is the light intensity;

[0021] The reverse saturation current

[0022] Among them, T r is the preset reference temperature, is the reference temperature T r The reverse saturation current, E g is the bandgap width of the photovoltaic cell;

[0023] An initial I value is preset, substituted into the right side of the equal sign of the current simulation model, and repeated calculation is performed by iteration until the difference between the I values ​​calculated successively meets the preset accuracy requirement, and then the final photovoltaic cell output current I is output;

[0024] Based on the series-parallel structure of photovoltaic cells, the photovoltaic cell output current I and photovoltaic cell output voltage V are adjusted accordingly to obtain the total photovoltaic current I total and the total photovoltaic voltage V total ;

[0025] Calculate the actual power output to the grid P g , the calculation formula is:

[0026] P g =ηI total V total

[0027] Among them, η is the inverter conversion efficiency, which is a known parameter of the inverter equipment.

[0028] According to a new energy power station grid-connected scheduling method provided by the present invention, in step three, the process of calculating and adjusting the output voltage and frequency of the photovoltaic power station based on the grid and power station parameters combined with the future output power includes:

[0029] Calculate the inverter output voltage reference value using the voltage regulation model The voltage regulation model is:

[0030]

[0031] Among them, V g is the measured value of the grid voltage, is the rated value of the grid voltage; K v is the voltage adjustment factor, which is used to consider the voltage regulation capability of the inverter and the tolerance of the grid to voltage fluctuations;

[0032] Calculate the inverter output frequency reference value using the frequency adjustment model The frequency adjustment model is:

[0033]

[0034] Among them, f g is the measured value of the power grid frequency; is the expected output power of the photovoltaic power station, which belongs to the rated value; P g is the actual power output to the grid; K f The frequency adjustment factor is used to consider the capacity of the PV power plant, the inertia of the power grid, and the tolerance of the power grid to frequency fluctuations;

[0035] Adjust the output voltage and output frequency of the inverter to meet the output voltage reference value and output frequency reference

[0036] According to a new energy power station grid-connected dispatching method provided by the present invention, the voltage adjustment coefficient L v The calculation formula is:

[0037]

[0038] Among them, V max and V min They represent the end values ​​of the voltage range that the inverter can adjust at its rated output power; V max -V min It represents the adjustable voltage range; α represents the voltage fluctuation range specified by the power grid within the rated voltage Within ±α%; represents the allowable voltage fluctuation range of the power grid; E is the coordination constant, which is used to convert K v The value range of is limited to between 0.1 and 0.5;

[0039] The frequency adjustment coefficient K f The calculation formula is:

[0040]

[0041] Among them, H is the grid inertia constant, which is used to reflect the grid's ability to resist frequency changes, P cap is the capacity of the photovoltaic power station, all of which belong to the rated value of the power grid.

[0042] According to a new energy power station grid-connected scheduling method provided by the present invention, in step 4, the process of synchronizing the output phase of the photovoltaic power station inverter with the grid phase includes:

[0043] Calculate the grid voltage phase angle θg The phase angle θ of the inverter output voltage after adjustment inv The error θ err , that is, θ err =θ g -θ inv ;

[0044] The output phase of the photovoltaic power station inverter is synchronized with the grid phase based on the synchronization model, and the synchronization model is:

[0045]

[0046] Among them, K P is the proportional gain, K i is the integral gain, which is determined based on the response speed and accuracy requirements of phase synchronization;

[0047] By continuously adjusting the trigger pulse phase of the inverter, the phase difference between the two is kept within the preset allowable range, ensuring that the current impact is minimized at the moment of grid connection.

[0048] According to a new energy power station grid-connected scheduling method provided by the present invention, in step five, the soft start current initial value I switch Set to the rated current of the preset ratio β, that is

[0049] According to a new energy power station grid-connected scheduling method provided by the present invention, in step five, grid-connected switching is performed when the phase difference between the grid voltage and the output voltage of the photovoltaic power station is less than a first threshold, and the voltage and frequency fluctuations are less than a second threshold.

[0050] A new energy power station grid-connected scheduling method provided according to the present invention also includes: during the soft start process, the current increases according to a preset slope, that is, the corresponding proportion of the rated current is increased in each sampling period until the rated current value of normal operation is reached.

[0051] According to a new energy power station grid-connected dispatching method provided by the present invention, the method further includes: feeding back a result after completing the grid-connected switching, and adjusting the voltage adjustment coefficient K accordingly based on the switching result. v And frequency adjustment factor K f , and perform iterative optimization.

[0052] Compared with the prior art, the beneficial effects of this application are:

[0053] This application uses a power prediction model established based on the physical characteristics of photovoltaic cells, comprehensively considering the impact of key factors such as light intensity and temperature on the output current of photovoltaic cells, and then accurately calculates the output power of photovoltaic power stations; under different light and temperature conditions, factors such as the linear relationship between photocurrent and light intensity in the model and the impact of temperature on reverse saturation current can more accurately reflect the actual power generation capacity of photovoltaic cells;

[0054] This application adopts a targeted voltage and frequency adjustment model to calculate the reference values ​​of the inverter output voltage and frequency according to the measured voltage and frequency of the power grid and the actual operating status of the photovoltaic power station (such as output power, etc.); in terms of voltage adjustment, by reasonably determining the voltage adjustment coefficient, the inverter can adjust the output voltage more accurately, so that it can quickly and stably match the grid voltage; in terms of frequency adjustment, the frequency adjustment coefficient determined based on factors such as the capacity of the photovoltaic power station and the inertia of the power grid enables the photovoltaic power station to respond to changes in the grid frequency in a timely manner, effectively adjust the output power, and maintain the stability of the grid frequency;

[0055] By using phase-locked loop technology combined with an accurate phase synchronization model, the present application can accurately measure the grid voltage phase angle and adjust the output phase angle of the photovoltaic power station inverter in real time; by reasonably setting the proportional gain and integral gain, the phase synchronization process has a fast response speed and high accuracy; when the grid is disturbed or the dynamic characteristics of the photovoltaic power station itself change, the influence of these adverse factors can be effectively overcome to ensure that the phase difference between the photovoltaic power station and the grid is always controlled within a very small range at the moment of grid connection and during the operation after grid connection;

[0056] During the entire grid-connected scheduling process, this application can automatically adjust the grid-connected strategy according to changes in system operating conditions (such as changes in grid load demand, changes in light intensity and temperature of photovoltaic power stations, etc.) by continuously collecting data and monitoring the operating status of the power grid and photovoltaic power stations in real time.

[0057] Other features and advantages of the present invention will be described in the following description, and partly become apparent from the description, or understood by practicing the present invention. The purpose and other advantages of the present invention can be realized and obtained by the structures particularly pointed out in the written description and the accompanying drawings.

[0058] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0059] The accompanying drawings are used to provide a further understanding of the present invention and constitute a part of the specification. Together with the embodiments of the present invention, they are used to explain the present invention and do not constitute a limitation of the present invention. In the accompanying drawings:

[0060] Figure 1It is a flow chart of a new energy power station grid-connected scheduling method provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0061] The preferred embodiments of the present invention are described below in conjunction with the accompanying drawings. It should be understood that the preferred embodiments described herein are only used to illustrate and explain the present invention, and are not used to limit the present invention.

[0062] Embodiment 1:

[0063] The present invention provides a method for scheduling a new energy power station to be connected to the grid. Figure 1 ,include:

[0064] Step 1: Collect the light intensity, temperature, photovoltaic panel output voltage and current data of the photovoltaic power station and the voltage, frequency and phase parameters of the grid side;

[0065] Step 2: predict the future output power of the photovoltaic power station based on the collected data;

[0066] Step 3: Calculate and adjust the output voltage and frequency of the photovoltaic power station based on the grid and power station parameters and the future output power to match the grid;

[0067] Step 4: Use phase-locked loop technology to synchronize the output phase of the photovoltaic power station inverter with the grid phase;

[0068] Step 5: After completing the matching adjustment, use the soft start technology to switch to the grid.

[0069] The principle and technical effect of this embodiment are as follows: by real-time monitoring of key parameters of the photovoltaic power station and the power grid (such as light intensity, temperature, voltage, current, frequency, phase, etc.), the system can be ensured to always grasp the latest operating status; based on the collected data, an algorithm or model is used to predict the output power of the photovoltaic power station in the future, which is helpful for advance planning and provides accurate information for power grid dispatching to cope with possible power fluctuations; in order to make the output of the photovoltaic power station as consistent as possible with the requirements of the power grid, it is necessary to adjust the output voltage and frequency of the power station according to the predicted output power and the parameters of the current power grid and power station. This dynamic adjustment helps to minimize the impact on the power grid and ensure the quality of power; the phase-locked loop (PLL) technology is used to synchronize the output phase of the photovoltaic power station inverter with the phase of the power grid; after completing all necessary adjustments, the soft start technology is used for grid-connected switching; the soft start can gradually increase the output power, thereby avoiding the impact of sudden loading on the power grid, protecting the equipment from damage, and reducing disturbances to the power grid.

[0070] In order to further optimize the above embodiment, in step 1, the process of collecting data includes:

[0071] By arranging high-precision light sensors and temperature sensors at different locations in the power station to obtain light intensity and temperature data, installing voltage and current transformers at the junction box and inverter of the photovoltaic array to obtain photovoltaic output voltage and current data, and directly obtaining grid-side voltage, frequency, and phase parameters from the grid monitoring equipment.

[0072] It should be noted that it is necessary to select a sensor with high accuracy (for example, the measurement error is within ±2%) and a wide measurement range (the light intensity can be measured in the range of 0-2000W / m 2 , light sensors and temperature sensors with a temperature measurement range of -40℃-80℃ and fast response speed (response time less than 1 second); when arranging sensors at different locations in the power station, follow the principle of uniform distribution to ensure that they can accurately reflect the changes in light and temperature in the entire power station area; for example, for large photovoltaic power stations, sensors can be arranged in different arrays and different orientations of the power station at a certain interval (such as one sensor per 100 square meters) to obtain comprehensive and representative data;

[0073] The data collected by the sensor is transmitted to the data collection center of the power station through wired (such as shielded twisted pair to reduce the impact of electromagnetic interference on data transmission) or wireless (such as ZigBee or Wi-Fi communication technology to ensure the stability and timeliness of data transmission) communication methods; at the data collection center, the collected light intensity and temperature data are pre-processed in real time, including data cleaning (removing abnormal values, such as obvious erroneous data caused by sensor failure or short-term occlusion) and data calibration (regularly calibrating the sensor according to known standard light intensity and temperature values ​​to ensure measurement accuracy);

[0074] Install high-precision voltage transformers (such as those with an accuracy level of 0.2) and current transformers (such as those with an accuracy level of 0.5) at the junction box and inverter of the photovoltaic array; the selection of the transformers should be based on the rated voltage, current and measurement accuracy requirements of the photovoltaic power station to ensure that the output voltage and current of the photovoltaic array can be accurately measured; for example, for a photovoltaic power station with a rated voltage of 1000V and a rated current of 500A, select a transformer with a suitable transformation ratio (such as 1000V / 100V, 500A / 5A) to convert high voltage and high current signals into low voltage and low current signals suitable for processing by data acquisition equipment;

[0075] The signal output by the transformer is collected by a data acquisition card (with a high sampling rate, such as above 10kHz, to accurately capture the changes in voltage and current); the collected analog signal is converted into a digital signal after analog-to-digital conversion (ADC) to facilitate subsequent data analysis and processing; in the process of data collection, attention should be paid to signal isolation and anti-interference measures, such as the use of photoelectric isolation technology to prevent the influence of power grid interference and other electromagnetic interference on data collection, to ensure that the collected voltage and current data are accurate and reliable;

[0076] When acquiring data directly from power grid monitoring equipment, ensure that the monitoring equipment has appropriate communication interfaces (such as RS-485, Ethernet interface, etc.) and communication protocols (such as Modbus, IEC61850, etc.); according to the communication interface and protocol requirements of the power grid monitoring equipment, configure the corresponding communication module and software driver in the power station's data acquisition system to achieve a stable communication connection with the power grid monitoring equipment; for example, if the power grid monitoring equipment adopts the Modbus communication protocol, install the Modbus communication driver in the power station data acquisition system and set the correct communication parameters (such as baud rate, data bit, stop bit, check bit, etc.) to ensure that the voltage, frequency, and phase parameters on the power grid side can be accurately read;

[0077] The data obtained from the power grid monitoring equipment is verified, including data format verification (to ensure that the data meets the specified format requirements), data range verification (to check whether parameters such as voltage, frequency, phase, etc. are within a reasonable range), etc. At the same time, in order to ensure the synchronization of data on the grid side and data on the photovoltaic power station side, time synchronization technology (such as the NTP protocol) is used to synchronize the data acquisition equipment and power grid monitoring equipment in the power station, so that the various types of data collected are consistent on the time axis, which is convenient for subsequent grid-connected scheduling analysis and control operations.

[0078] In order to further optimize the above embodiment, in step 2, the process of predicting the future output power of the photovoltaic power station includes:

[0079] The current simulation model is used to calculate the output current I of the photovoltaic cell. The current simulation model is:

[0080]

[0081] Where I is the photovoltaic cell output current obtained through model simulation; I ph is the photocurrent, I0 is the reverse saturation current, q is the electron charge, V is the current output voltage of the photovoltaic cell, R s is the series resistance, R sh is the parallel resistance, n is the diode characteristic factor, k is the Boltzmann constant, and T is the photovoltaic cell temperature;

[0082] Photocurrent I ph =KI G; K I is the proportionality coefficient, which depends on the material and structural characteristics of the photovoltaic cell, and G is the light intensity;

[0083] Reverse saturation current

[0084] Among them, T r is the preset reference temperature, is the reference temperature T r The reverse saturation current, E g is the bandgap width of the photovoltaic cell; all are equipment parameters that can be obtained by searching;

[0085] An initial I value is set in advance, and it is substituted into the right side of the equal sign of the current simulation model. The calculation is repeated through the iteration method until the difference between the I values ​​calculated successively meets the preset accuracy requirement, and then the final photovoltaic cell output current I is output;

[0086] Based on the series-parallel structure of photovoltaic cells, the photovoltaic cell output current I and photovoltaic cell output voltage V are adjusted accordingly to obtain the total photovoltaic current I total and the total photovoltaic voltage V total ;

[0087] Calculate the actual power output to the grid P g , the calculation formula is:

[0088] P g =ηI total V total

[0089] Among them, η is the inverter conversion efficiency, which is a known parameter of the inverter equipment.

[0090] It should be noted that for the proportionality coefficient K I For photovoltaic cells of specific materials and structures, experimental measurements can be carried out under standard test conditions, and the proportionality coefficient K can be inferred by measuring the photocurrent under different light intensities. I Or, according to the material properties of photovoltaic cells (such as the bandgap width and absorption coefficient of semiconductor materials) and structural parameters (such as cell thickness and surface reflectivity), theoretical calculations can be performed using semiconductor physics theory and related photovoltaic cell models. At the same time, simulations can be performed with the help of professional photovoltaic cell simulation software (such as PC1D, AMPS, etc.). Input the material and structural parameters of the photovoltaic cell into the simulation software, simulate the photocurrent under different light intensities, and then reversely calculate K according to the formula. I At the same time, the theoretical calculation results are compared and verified with the simulation results to further optimize K I value;

[0091] For the I value, the initial I value is estimated based on the working characteristics of the photovoltaic cell and previous empirical data. Generally speaking, under normal light and temperature conditions, the output current of the photovoltaic cell will be within a certain range. For example, for common silicon photovoltaic cells, under standard light intensity, its output current density is about 30-40mA / cm 2 ; If the area of ​​the photovoltaic cell is known, a rough current value can be estimated as the initial I value; assuming that the area of ​​the photovoltaic cell is 100 square centimeters, the initial I value can be estimated to be 3-4A.

[0092] In order to further optimize the above embodiment, in step 3, the process of calculating and adjusting the output voltage and frequency of the photovoltaic power station according to the grid and power station parameters combined with the future output power includes:

[0093] Calculate the inverter output voltage reference value using the voltage regulation model The voltage regulation model is:

[0094]

[0095] Among them, V g is the measured value of the grid voltage, is the rated value of the grid voltage; K v is the voltage adjustment factor, which is used to consider the voltage regulation capability of the inverter and the tolerance of the grid to voltage fluctuations;

[0096] Calculate the inverter output frequency reference value using the frequency adjustment model The frequency adjustment model is:

[0097]

[0098] Among them, f g is the measured value of the power grid frequency; is the expected output power of the photovoltaic power station, which belongs to the rated value; P g is the actual power output to the grid; K f The frequency adjustment factor is used to consider the capacity of the PV power plant, the inertia of the power grid, and the tolerance of the power grid to frequency fluctuations;

[0099] Adjust the output voltage and output frequency of the inverter to meet the output voltage reference value and output frequency reference

[0100] Among them, the voltage adjustment coefficient K v The calculation formula is:

[0101]

[0102] Among them, V maxand V min They represent the end values ​​of the voltage range that the inverter can adjust at its rated output power; V max -V min It represents the adjustable voltage range; α represents the voltage fluctuation range specified by the power grid within the rated voltage Within ±α%; represents the allowable voltage fluctuation range of the power grid; E is the coordination constant, which is used to convert K v The value range of is limited to between 0.1 and 0.5;

[0103] Frequency adjustment factor K f The calculation formula is:

[0104]

[0105] Among them, H is the grid inertia constant, which is used to reflect the grid's ability to resist frequency changes, P cap is the capacity of the photovoltaic power station, all of which belong to the rated value of the power grid.

[0106] It should be noted that if K v The value of is too large, for example, greater than 0.5. When the grid voltage fluctuates slightly, the inverter will make a large adjustment to the output voltage according to the voltage adjustment model. This excessive adjustment may cause the fluctuation of the inverter output voltage to intensify, which in turn causes instability in the entire photovoltaic power generation system. Because the photovoltaic power generation system and the grid are interconnected, the instability of the inverter output voltage will affect the power quality of the grid, which may cause abnormal operation of other electrical equipment in the grid and even cause the grid protection device to malfunction, causing the system to trip and power off, seriously affecting the stable operation of the power system.

[0107] When K v If the value is too small, such as less than 0.1, although the system instability caused by excessive adjustment can be avoided, it will cause the inverter to respond too slowly to grid voltage fluctuations; when the grid voltage changes, the inverter needs a long time to adjust the output voltage to a value that matches the grid. During this period, there may be a large deviation between the output voltage of the photovoltaic power station and the grid voltage, affecting the grid-connected power quality, and in the case of rapid changes in grid voltage (such as when the grid fails or the load suddenly changes), it may not be possible to adjust the output voltage to the appropriate range in a timely and effective manner, resulting in grid connection failure or impact on the grid; while the value is between 0.1 and 0.5, it can ensure a certain adjustment speed while avoiding instability caused by excessive adjustment, thereby achieving a better balance between adjustment speed and accuracy;

[0108] The hardware characteristics and control capabilities of the inverter itself have an impact on K vThe value of K is also limited; the power electronic devices (such as IGBT, etc.) inside the inverter have certain switching frequency and response speed limitations. v If the value exceeds the appropriate range, the inverter control circuit may not work properly, resulting in failure to achieve the expected voltage regulation effect; for example, a too large K v The value may cause the inverter control signal to exceed its maximum allowable value, resulting in the power electronic device failing to switch normally, and thus failing to accurately adjust the output voltage; the value range of 0.1 to 0.5 is determined based on the performance characteristics of common inverters, and can ensure that the inverter can effectively adjust the output voltage within the normal working range and match the grid voltage to achieve stable and efficient grid-connected operation.

[0109] To further optimize the above embodiment, in step 4, the process of synchronizing the output phase of the photovoltaic power station inverter with the grid phase includes:

[0110] Calculate the grid voltage phase angle θ g The phase angle θ of the inverter output voltage after adjustment inv The error θ err , that is, θ err =θ g -θ inv ;

[0111] The output phase of the photovoltaic power station inverter is synchronized with the grid phase based on the synchronization model. The synchronization model is:

[0112]

[0113] Among them, K P is the proportional gain, K i is the integral gain, which is determined based on the response speed and accuracy requirements of phase synchronization;

[0114] By continuously adjusting the trigger pulse phase of the inverter, the phase difference between the two is kept within the preset allowable range, ensuring that the current impact is minimized at the moment of grid connection.

[0115] It should be noted that in the actual photovoltaic power station grid-connected system, different K P and K i The influence of K value on the phase synchronization response speed. First, set an initial K P and K i Then apply a simulated phase step signal to the system (simulating a sudden change in the grid phase) and observe the response curve of the inverter output phase. If the response speed is too slow (such as the time required to reach a stable phase exceeds expectations), gradually increase K P value, and adjust K appropriately ivalue, and test again until a K that meets the response speed requirements is found. P and K i In this process, it is necessary to record the response curves under different parameter combinations for comparison and analysis.

[0116] In order to further optimize the above embodiment, in step 5, it is also included in the grid-connected switching process that the soft start current initial value I switch Set to the rated current of the preset ratio β, that is

[0117] It should be noted that for the preset ratio β, first, it is necessary to perform parameter analysis on the equipment of the photovoltaic power station (such as inverters, transformers, etc.) and the equipment on the grid side (such as switchgear, cables, etc.). Understand the key parameters of these equipment such as the rated current and short-time withstand current. From the perspective of equipment safety, the preset ratio should ensure that the current will not cause excessive impact on the equipment in the initial stage of soft start to ensure the insulation performance and service life of the equipment. For example, for the inverter, its internal power semiconductor devices (such as IGBT) have certain current carrying capacity limitations. According to its data sheet, its allowed short-time overcurrent multiple may be 1.2-1.5 times the rated current. Considering a certain safety margin (such as 80%), the preset ratio of the initial value of the soft start current can be preliminarily determined to be between 0.8*1.2=0.96 (i.e. 96%) and 0.8*1.5=1.2 (i.e. 120%).

[0118] In order to further optimize the above embodiment, in step five, the grid connection switching is performed when the phase difference between the grid voltage and the output voltage of the photovoltaic power station is less than the first threshold and the voltage and frequency fluctuations are less than the second threshold.

[0119] It should be noted that the voltage and frequency fluctuation data of the photovoltaic power station during actual operation and the relevant data during grid-connected operation are collected. These data are analyzed to understand the characteristics and laws of voltage and frequency fluctuations under different working conditions (such as different light intensity, different grid load, etc.). According to the actual operation experience, a second threshold value is determined to ensure the stable operation of the grid and adapt to the normal operation changes of the photovoltaic power station. For example, through the statistical analysis of the operation data of a photovoltaic power station for one year, it is found that the voltage fluctuation is generally within ±3% of the rated voltage and the frequency fluctuation is within ±0.1Hz during normal operation, but in special weather or sudden changes in grid load, the fluctuation may increase. Taking these situations into consideration, the voltage fluctuation threshold is set to ±3.5% of the rated voltage and the frequency fluctuation threshold is set to ±0.15Hz. In this way, while ensuring the stability of the grid and the normal operation of the equipment, the actual operation of the photovoltaic power station is taken into account, and the feasibility and reliability of grid-connected operation are improved.

[0120] In order to further optimize the above embodiment, it also includes: during the soft start process, the current increases according to a preset slope, that is, the corresponding proportion of the rated current is increased in each sampling period until the rated current value of normal operation is reached.

[0121] It should be noted that for the preset slope, it is necessary to consider the characteristics of the output power of the photovoltaic power station changing with the light intensity to determine the preset slope. During the soft start process, it is hoped that the increase in the grid-connected current matches the increase in the output power of the photovoltaic power station to achieve efficient energy conversion and stable grid-connected operation. According to the light change law of the location of the photovoltaic power station (such as the light gradually increases in the morning, the strongest at noon, and weakens in the evening) and the output characteristic curve of the photovoltaic cell, the power change rate under different light intensities is analyzed. For example, when the light intensity increases slowly in the morning, the output power of the photovoltaic power station also rises slowly. At this time, the preset slope can be set to a smaller value to increase the grid-connected current slowly; when the light intensity is stable and strong at noon, the power output is relatively stable, and the preset slope can be appropriately adjusted to a value that matches the stable power output; when the light weakens in the evening, the power decreases, and the preset slope should also be reduced accordingly to avoid excessive current and power mismatch. By analyzing the relationship between light intensity and power output, a preset slope curve that changes with time and light conditions is determined to optimize the soft start process.

[0122] The photovoltaic power station system itself has a certain inertia, including the capacitance characteristics of photovoltaic cells, the control response time of the inverter, etc. If the preset slope is too large, the system may not be able to respond to the rapid change of current in time, resulting in unstable control; if the preset slope is too small, the soft start time will be too long, affecting the grid connection efficiency. By testing and analyzing the inertia of the photovoltaic power station system (such as measuring the time constant and other parameters of the system), the preset slope is determined by weighing the system response capability and soft start efficiency. For example, for systems with large inertia and long response time, the preset slope should be set smaller to ensure that the system can stably control the current; for systems with small inertia and fast response speed, the preset slope can be appropriately increased, but the limitations of the equipment and the power grid still need to be considered. At the same time, the preset slope in different seasons and weather conditions can be dynamically adjusted according to the actual operation situation to achieve the best soft start effect and improve the overall performance of the photovoltaic power station.

[0123] In order to further optimize the above embodiment, it also includes: after completing the grid-connected switching, feedback results are fed back, and the voltage adjustment coefficient K is adjusted accordingly based on the switching results. v And frequency adjustment factor K f , and perform iterative optimization.

[0124] It should be noted that after the grid connection switching is completed, the relevant operating data of the photovoltaic power station and the power grid are continuously collected, including but not limited to the output voltage, output current, output power of the photovoltaic power station, the voltage, frequency, phase on the grid side, and the magnitude of the impact current at the moment of grid connection and after grid connection, power quality indicators (such as harmonic content, voltage fluctuation, etc.). These data will serve as the basis for evaluating the grid connection effect and subsequent optimization and adjustment. For example, through the high-precision sensors installed in the photovoltaic array junction box, the inverter output terminal and the grid access point, the above data can be obtained in real time and transmitted to the data processing unit for storage and analysis.

[0125] Determine the key indicators for evaluating grid-connected performance, such as the ratio of the peak value of the grid-connected impulse current to the rated current (inrush current ratio), the fluctuation range of voltage and frequency after grid connection (such as the percentage of the peak-to-peak value of voltage fluctuation to the rated voltage, the percentage of the maximum deviation of frequency fluctuation to the rated frequency), and whether the power quality indicators meet the relevant standards (such as whether the harmonic content is lower than the specified limit).

[0126] The actual evaluation index calculated from the collected data is compared with the set ideal index. If all evaluation indicators meet the requirements, the current grid-connected dispatching parameters (voltage adjustment coefficient and frequency adjustment coefficient) are considered appropriate and no optimization adjustment is required for the time being. However, if any evaluation indicator does not meet the requirements, the iterative optimization process is started.

[0127] The iterative optimization process is similar to the gradient descent algorithm and will not be elaborated on in detail.

[0128] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for grid-connected dispatching of a new energy power station, characterized in that: include: Step 1: Collect the light intensity, temperature, photovoltaic panel output voltage and current data of the photovoltaic power station and the voltage, frequency and phase parameters of the grid side; Step 2: predict the future output power of the photovoltaic power station based on the collected data; Step 3: Calculate and adjust the output voltage and frequency of the photovoltaic power station based on the grid and power station parameters and the future output power to match the grid; Step 4: Synchronize the output phase of the photovoltaic power station inverter with the grid phase using phase-locked loop technology; Step 5: After completing the matching adjustment, use the soft start technology to switch to the grid.

2. A new energy power station grid-connected dispatching method according to claim 1, characterized in that: In step one, the process of collecting data includes: By arranging high-precision light sensors and temperature sensors at different locations in the power station to obtain light intensity and temperature data, installing voltage and current transformers at the junction box and inverter of the photovoltaic array to obtain photovoltaic output voltage and current data, and directly obtaining grid-side voltage, frequency, and phase parameters from the grid monitoring equipment.

3. A new energy power station grid-connected dispatching method according to claim 2, characterized in that: In step 2, the process of predicting the future output power of the photovoltaic power station includes: The photovoltaic cell output current I is calculated using a current simulation model, and the current simulation model is: Where I is the photovoltaic cell output current obtained through model simulation; I ph is the photocurrent, I0 is the reverse saturation current, q is the electron charge, V is the current output voltage of the photovoltaic cell, R s is the series resistance, R sh is the parallel resistance, n is the diode characteristic factor, k is the Boltzmann constant, and T is the photovoltaic cell temperature; The photocurrent I ph =K I G; K I is the proportionality coefficient, which depends on the material and structural characteristics of the photovoltaic cell, and G is the light intensity; The reverse saturation current Among them, T r is the preset reference temperature, is the reference temperature T r The reverse saturation current, E g is the bandgap width of the photovoltaic cell; An initial I value is preset, substituted into the right side of the equal sign of the current simulation model, and repeated calculation is performed by iteration until the difference between the I values ​​calculated successively meets the preset accuracy requirement, and then the final photovoltaic cell output current I is output; Based on the series-parallel structure of photovoltaic cells, the photovoltaic cell output current I and photovoltaic cell output voltage V are adjusted accordingly to obtain the total photovoltaic current I total and the total photovoltaic voltage V total ; Calculate the actual power output to the grid P g , the calculation formula is: P g =ηI total V total Among them, η is the inverter conversion efficiency, which is a known parameter of the inverter equipment.

4. A new energy power station grid-connected dispatching method according to claim 3, characterized in that: In step three, the process of calculating and adjusting the output voltage and frequency of the photovoltaic power station based on the grid and power station parameters combined with the future output power includes: Calculate the inverter output voltage reference value using the voltage regulation model The voltage regulation model is: Among them, V g is the measured value of the grid voltage, is the rated value of the grid voltage; K v is the voltage adjustment factor, which is used to consider the voltage regulation capability of the inverter and the tolerance of the grid to voltage fluctuations; Calculate the inverter output frequency reference value using the frequency adjustment model The frequency adjustment model is: Among them, f g is the measured value of the power grid frequency; is the expected output power of the photovoltaic power station, which belongs to the rated value; P g is the actual power output to the grid; K f The frequency adjustment factor is used to consider the capacity of the PV power plant, the inertia of the power grid, and the tolerance of the power grid to frequency fluctuations; Adjust the output voltage and output frequency of the inverter to meet the output voltage reference value and output frequency reference 5. A new energy power station grid-connected dispatching method according to claim 4, characterized in that: The voltage adjustment factor K v The calculation formula is: Among them, V max and V min They represent the end values ​​of the voltage range that the inverter can adjust at its rated output power; V max -V min It represents the adjustable voltage range; α represents the voltage fluctuation range specified by the power grid within the rated voltage Within ±α%; represents the allowable voltage fluctuation range of the power grid; E is the coordination constant, which is used to convert K v The value range of is limited to between 0.1 and 0.5; The frequency adjustment coefficient K f The calculation formula is: Among them, H is the grid inertia constant, which is used to reflect the grid's ability to resist frequency changes, P cap is the capacity of the photovoltaic power station, all of which belong to the rated value of the power grid.

6. A new energy power station grid-connected dispatching method according to claim 5, characterized in that: In step 4, the process of synchronizing the output phase of the photovoltaic power station inverter with the grid phase includes: Calculate the grid voltage phase angle θ g The phase angle θ of the inverter output voltage after adjustment inv The error θ err , that is, θ err =θ g -θ inv ; The output phase of the photovoltaic power station inverter is synchronized with the grid phase based on the synchronization model, and the synchronization model is: Among them, K P is the proportional gain, K i is the integral gain, which is determined based on the response speed and accuracy requirements of phase synchronization; By continuously adjusting the trigger pulse phase of the inverter, the phase difference between the two is kept within the preset allowable range, ensuring that the current impact is minimized at the moment of grid connection.

7. A new energy power station grid-connected dispatching method according to claim 6, characterized in that: In step 5, the initial value of the soft start current I switch Set to the rated current of the preset ratio β, that is 8. A new energy power station grid-connected dispatching method according to claim 7, characterized in that: In step five, the grid connection switching is performed when the phase difference between the grid voltage and the output voltage of the photovoltaic power station is less than a first threshold value, and the voltage and frequency fluctuations are less than a second threshold value.

9. A new energy power station grid-connected dispatching method according to claim 8, characterized in that: Also includes: During the soft start process, the current increases according to the preset slope, that is, the corresponding proportion of the rated current is increased in each sampling period until the rated current value for normal operation is reached.

10. A new energy power station grid-connected dispatching method according to claim 9, characterized in that: Also includes: Feedback the result after the grid-connected switching is completed, and adjust the voltage adjustment coefficient K accordingly based on the switching result. v And frequency adjustment factor K f , and perform iterative optimization.

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