Grid-connection scheduling method for new energy power station

Abstract

The present invention relates to the technical field of power system scheduling, and provides a grid-connection scheduling method for a new energy power station, comprising: collecting light intensity, temperature, photovoltaic panel output voltage and current data of a photovoltaic power station, as well as voltage, frequency and phase parameters of a grid side; predicting a future output power of the photovoltaic power station on the basis of the collected data; calculating and adjusting, by means of grid and power station parameters together with the future output power, an output voltage and an output frequency of the photovoltaic power station to match the grid; synchronizing an output phase of a photovoltaic power station inverter with a grid phase by using phase-locked loop technology; and after the matching adjustment is completed, performing grid-connection switching by using soft-start technology. The present invention ensures, by means of an innovative grid-connection scheduling mode and a precise mathematical model, that the photovoltaic power station can be smoothly and efficiently connected to the grid, and also maintains power quality and grid stability, better adapting to the operational requirements of a power system.

Description

A new energy power station grid-connected scheduling method TECHNICAL FIELD

[0001] The present application relates to the technical field of power system scheduling, in particular to a new energy power station grid-connected scheduling method. BACKGROUND

[0002] With the growing demand for clean energy and the increasing awareness of environmental protection, photovoltaic power generation as a sustainable and renewable energy utilization method has developed rapidly. In recent years, photovoltaic power generation technology has made continuous progress, and the conversion efficiency of photovoltaic cells has gradually improved, and the cost has continued to decline. Large-scale photovoltaic power stations have emerged, not only playing an important role in distributed energy supply, but also occupying an increasingly large share in centralized power generation; for example, in some sunny areas, photovoltaic power generation has become an important part of local power supply, making a positive contribution to reducing dependence on traditional fossil fuels; at the same time, with the development of energy storage technology, the combination of photovoltaic power generation and energy storage systems provides a new solution to improve the stability and reliability of energy, further promoting the widespread application of photovoltaic power generation in the power field.

[0003] However, the existing photovoltaic power generation power prediction method has low prediction accuracy under complex operating conditions; inaccurate power prediction will lead to unreasonable grid scheduling, and when the actual photovoltaic power generation power deviates greatly from the predicted value, it may cause imbalance between supply and demand of the power grid.

[0004] At the same time, achieving phase synchronization between photovoltaic power stations and the power grid is one of the key steps of grid connection; however, in the phase synchronization process, the existing technology is easily affected by power grid interference and the dynamic characteristics of photovoltaic power stations themselves, leading to 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 power grid and photovoltaic power stations, reducing the service life of the equipment, and even possibly causing power grid failure; for example, in some cases where the power grid fluctuates greatly, the traditional phase synchronization method may not be able to adjust the output phase of the inverter in time and accurately, leading to grid connection failure or unstable system operation after grid connection;

[0005] The existing grid-connected scheduling method mostly lacks adaptive adjustment capability for changes in the operating state of the power grid and photovoltaic power stations; the load demand, topology structure of the power grid, and the performance of photovoltaic power stations themselves may change over time, but traditional technology is difficult to optimize grid-connected scheduling strategies in real time according to these changes; this makes it impossible for photovoltaic power stations to always maintain optimal grid-connected operating states 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 problems. SUMMARY

[0007] The present application provides a new energy power station grid-connected scheduling method, aiming to solve the problems existing in the prior art, through innovative grid-connected scheduling mode and accurate mathematical model, to ensure that the photovoltaic power station can be smoothly and efficiently connected to the power grid, while maintaining power quality and grid stability, and better adapting to the operation demand of the power system.

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

[0009] Step one, collect photovoltaic power station and grid side data, the photovoltaic power station data includes light intensity, temperature, photovoltaic cell output voltage and current data; The grid side data includes voltage, frequency and phase parameters;

[0010] Step two, predict the future output power of the photovoltaic power station according to the collected photovoltaic power station and grid side data;

[0011] Step three, based on the photovoltaic power station and grid side data combined with the future output power, calculate and adjust the output voltage and frequency of the photovoltaic power station inverter, so that it matches the grid;

[0012] Step four, based on the adjusted output voltage and frequency, use the phase-locked loop technology to synchronize the output phase of the photovoltaic power station inverter with the grid phase;

[0013] Step five, after completing the voltage, frequency and phase matching and synchronization adjustment between the photovoltaic power station and the grid through steps three and four, use soft start technology to perform grid-connected switching between the photovoltaic power station and the grid.

[0014] According to the new energy power station grid-connected scheduling method provided by the present application, in step one, the process of collecting photovoltaic power station and grid side data includes:

[0015] By arranging light sensors and temperature sensors at different positions in the photovoltaic power station to obtain light intensity and temperature data, installing voltage transformers and current transformers at the bus box and inverter of the photovoltaic array to obtain photovoltaic cell output voltage and current data, and obtaining voltage, frequency and phase parameters from the grid monitoring equipment.

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

[0017] Use current simulation model to calculate photovoltaic cell output current , the current simulation model is:

[0018]

[0019] in, The output current of the photovoltaic cell is obtained through model simulation; For photocurrent, It is the reverse saturation current. The amount of electron charge. This is the current output voltage of the photovoltaic cell. For series resistance, For parallel resistors, This is the diode characteristic factor. Boltzmann's constant, The temperature of the photovoltaic cell;

[0020] The photogenerated current ;in This is a proportionality coefficient, which depends on the material and structural characteristics of the photovoltaic cell. Light intensity;

[0021] The reverse saturation current ;

[0022] in, For the preset reference temperature, Reference temperature The reverse saturation current under, The bandgap width of a photovoltaic cell;

[0023] Setting the initial output current of the photovoltaic cell The value is substituted into the current simulation model, and the calculation is iteratively updated until the result obtained from two consecutive calculations is obtained. If the difference in values ​​meets the preset accuracy requirements, then the final photovoltaic cell output current will be output. ;

[0024] The series-parallel structure of photovoltaic cells corresponds to the adjustment of the output current of the photovoltaic cells. and photovoltaic cell output voltage The total photovoltaic current is obtained. and total photovoltaic voltage ;

[0025] Calculate the actual power output to the power grid This refers to the future output power of the photovoltaic power station, calculated using the following formula:

[0026]

[0027] in, This refers to the inverter conversion efficiency, which is a known parameter of the inverter equipment.

[0028] According to the new energy power station grid-connected scheduling method provided by the application, in step three, the process of calculating and adjusting the output voltage and frequency of the photovoltaic power station based on photovoltaic power station and grid side data and future output power comprises:

[0029] The voltage adjustment model is used to calculate the inverter output voltage reference value , and the voltage adjustment model is as follows:

[0030]

[0031] , wherein, is the measured value of the grid voltage, is the rated value of the grid voltage; is the voltage adjustment coefficient, which is used to consider the voltage regulation capability of the inverter and the tolerance of the grid to voltage fluctuation;

[0032] The frequency adjustment model is used to calculate the inverter output frequency reference value , and the frequency adjustment model is as follows:

[0033]

[0034] , wherein, is the measured value of the grid frequency; is the expected output power of the photovoltaic power station, which is the rated value; is the actual output power to the grid; is the frequency adjustment coefficient, which is used to consider the capacity of the photovoltaic power station, the inertia of the grid and the tolerance of the grid to frequency fluctuation;

[0035] The output voltage and the output frequency of the inverter are adjusted to meet the output voltage reference value and the output frequency reference value .

[0036] According to the new energy power station grid-connected scheduling method provided by the application, the calculation formula of the voltage adjustment coefficient is as follows:

[0037]

[0038] , wherein, and are the range end point values of the voltage regulated by the inverter at its rated output power, i.e. the maximum value and the minimum value; is the adjustable voltage range; is the voltage fluctuation range allowed by the grid, which is within ± of the rated voltage ; is the allowed grid voltage fluctuation range; is a coordination constant for limiting the value range of to between 0.1 and 0.5;

[0039] the frequency adjustment coefficient is calculated by the formula:

[0040]

[0041] wherein, is a grid inertia constant for reflecting the ability of the grid to resist frequency changes, is a photovoltaic power station capacity, both of which are grid rated values.

[0042] According to the new energy power station grid-connected scheduling method provided by the application, in step four, the process of synchronizing the phase of the photovoltaic power station inverter output with the phase of the grid by using the phase-locked loop technology includes:

[0043] calculating the error between the grid voltage phase angle and the phase angle of the adjusted inverter output voltage , that is, ;

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

[0045]

[0046] wherein, is a proportional gain, is an 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 within the preset allowable range, so as to ensure that the current impact is minimum at the grid-connected moment.

[0048] According to the new energy power station grid-connected scheduling method provided by the application, in step five, during the grid-connected switching process, the initial value of the soft start current is set to be a preset proportion of the rated current, that is, .

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

[0050] ​According to the grid-connected scheduling method for a new energy power plant provided by the present invention, the grid-connected current is increased according to a preset slope during the soft start process, that is, the rated current is increased by a corresponding proportion in each sampling period until the rated current value for normal operation is reached.

[0051] According to the grid-connected dispatching method for a new energy power plant provided by the present invention, the method further includes: feeding back the result after the grid connection switch is completed, and adjusting the voltage adjustment coefficient accordingly based on the switch result. and frequency adjustment coefficient Iterative optimization is then carried out.

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

[0053] This application establishes a power prediction model based on the physical characteristics of photovoltaic cells, comprehensively considering the influence of key factors such as light intensity and temperature on the output current of photovoltaic cells, and thus accurately calculates the output power of photovoltaic power plants. Under different light and temperature conditions, the linear relationship between the photogenerated current and light intensity in the model, as well as the influence of temperature on the reverse saturation current, can more accurately reflect the actual power generation capacity of photovoltaic cells.

[0054] This application employs targeted voltage and frequency adjustment models, calculating reference values ​​for inverter output voltage and frequency based on measured grid voltage and frequency, as well as the actual operating status of the photovoltaic power station (such as output power). Regarding voltage adjustment, by rationally determining the voltage adjustment coefficient, the inverter can more accurately regulate its output voltage, enabling it to quickly and stably match the grid voltage. Regarding frequency adjustment, the frequency adjustment coefficient, determined based on factors such as photovoltaic power station capacity and grid inertia, allows the photovoltaic power station to respond promptly to grid frequency changes, effectively adjust output power, and maintain grid frequency stability.

[0055] By utilizing phase-locked loop (PLL) technology combined with a precise phase synchronization model, this 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 there is grid interference or changes in the dynamic characteristics of the photovoltaic power station itself, it can effectively overcome the influence of these adverse factors and ensure that the phase difference between the photovoltaic power station and the grid is always controlled within a very small range during the moment of grid connection and during the operation after grid connection.

[0056] Throughout the grid connection and dispatch process, this application continuously collects data and monitors the operating status of the power grid and photovoltaic power stations in real time. It can automatically adjust the grid connection strategy according to changes in system operation (such as changes in grid load demand, changes in solar irradiance and temperature at photovoltaic power stations, etc.).

[0057] Other features and advantages of the invention will be set forth in the following description, and will be apparent in part from the description, or may be learned by practicing the invention. The objects and other advantages of the invention may be realized and obtained by means of the structures particularly pointed out in the written description and the accompanying drawings.

[0058] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0059] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used in conjunction with embodiments of the invention to explain the invention and do not constitute a limitation thereof. In the drawings:

[0060] Figure 1 is a flowchart illustrating a grid-connected scheduling method for a new energy power plant provided in an embodiment of the present invention. Embodiments of the present invention

[0061] The preferred embodiments of the present invention will be described below with reference to the accompanying drawings. It should be understood that the preferred embodiments described herein are for illustration and explanation only and are not intended to limit the present invention.

[0062] Example 1:

[0063] This invention provides a grid-connected dispatch method for new energy power plants, as shown in Figure 1, including:

[0064] Step 1: Collect data on the solar power plant's irradiance, temperature, photovoltaic panel output voltage and current, as well as the grid-side voltage, frequency, and phase parameters;

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

[0066] Step 3: Based on the grid and power plant parameters and the future output power, calculate and adjust the output voltage and frequency of the photovoltaic power plant to match the grid.

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

[0068] Step 5: After completing the matching and adjustment, use soft-start technology to perform grid connection switching.

[0069] The principle and technical effects of this embodiment are as follows: By monitoring key parameters of the photovoltaic power station and the power grid in real time (such as light intensity, temperature, voltage, current, frequency, phase, etc.), the system can always keep track of the latest operating status; based on the collected data, algorithms or models are used to predict the output power of the photovoltaic power station in the future, which helps to plan ahead and provides accurate information for grid dispatch to cope with possible power fluctuations; in order to make the output of the photovoltaic power station as compatible as possible with the requirements of the power grid, the output voltage and frequency of the power station need to be adjusted according to the predicted output power and the current parameters of the power grid and the power station. This dynamic adjustment helps to minimize the impact on the power grid and ensure power quality; 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 the necessary adjustments, soft-start technology is used for grid connection switching; 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] Phase-locked loop (PLL) technology is a control technique that achieves signal phase synchronization, ensuring that the output signal maintains the same phase as the input reference signal, while simultaneously enabling the output frequency to stably track the reference frequency. It enables precise phase locking and frequency tracking of signals.

[0071] Soft-start technology is a technique used to control the startup process of equipment (especially motors and high-power electrical equipment). Through specific circuits or control algorithms, it avoids excessive inrush current and torque at the moment of power-on, achieving a smooth startup process from low voltage and low current to rated voltage and current. This protects the equipment and related circuit systems, extends equipment lifespan, and reduces the impact on the power grid.

[0072] To further optimize the above embodiments, the data acquisition process in step one includes:

[0073] By deploying high-precision light and temperature sensors at different locations within the power plant to acquire data on light intensity and photovoltaic cell temperature, and by installing voltage and current transformers at the combiner boxes and inverters of the photovoltaic array to acquire data on the output voltage and current of the photovoltaic cells, the voltage, frequency, and phase parameters on the grid side can be directly obtained from the grid monitoring equipment.

[0074] It should be noted that high-precision light and temperature sensors (e.g., measurement error within ±2%), wide measurement range (light intensity measurement range of 0-2000W / m², temperature measurement range of -40℃-80℃), and fast response speed (response time less than 1 second) should be selected. When deploying sensors in different locations within the power station, a uniform distribution principle should be followed to ensure accurate reflection of light and temperature changes throughout the entire power station area. For example, for large photovoltaic power stations, sensors can be deployed at certain intervals (e.g., one sensor per 100 square meters) in different arrays and facing areas of the power station to obtain comprehensive and representative data.

[0075] Data collected by light and temperature sensors is transmitted to the power plant's data acquisition center via wired (e.g., using shielded twisted-pair cables to reduce the impact of electromagnetic interference on data transmission) or wireless (e.g., using ZigBee or Wi-Fi communication technologies to ensure the stability and timeliness of data transmission) communication methods. At the data acquisition center, the collected light intensity and temperature data undergo real-time preprocessing, including data cleaning (removing outliers, such as obvious erroneous data caused by sensor failure or temporary shading) and data calibration (periodically calibrating the sensors according to known standard light intensity and temperature values ​​to ensure measurement accuracy).

[0076] High-precision voltage transformers (e.g., accuracy class 0.2) and current transformers (e.g., accuracy class 0.5) should be installed at the combiner boxes and inverters of the photovoltaic array. The selection of voltage and current transformers should be based on the rated voltage, current, and measurement accuracy requirements of the photovoltaic power station to ensure accurate measurement of the output voltage and current of the photovoltaic array. For example, for a photovoltaic power station with a rated voltage of 1000V and a rated current of 500A, transformers with appropriate ratios (e.g., 1000V / 100V, 500A / 5A) should be selected to convert high-voltage, high-current signals into low-voltage, low-current signals suitable for data acquisition equipment processing.

[0077] The signals output from voltage transformers and current transformers are acquired by a data acquisition card (with a high sampling rate, such as 10kHz or higher, to accurately capture changes in voltage and current). The acquired analog signals are converted into digital signals by analog-to-digital converter (ADC) for subsequent data analysis and processing. During the data acquisition process, attention should be paid to signal isolation and anti-interference measures, such as using opto-isolation technology to prevent the influence of power grid interference and other electromagnetic interference on data acquisition, and to ensure that the acquired voltage and current data are accurate and reliable.

[0078] When acquiring data directly from power grid monitoring equipment, ensure that the monitoring equipment has suitable communication interfaces (such as RS-485, Ethernet interface, etc.) and communication protocols (such as Modbus, IEC61850, etc.). Based on the communication interface and protocol requirements of the power grid monitoring equipment, configure the corresponding communication modules and software drivers in the power plant's data acquisition system to achieve a stable communication connection with the power grid monitoring equipment. For example, if the power grid monitoring equipment uses the Modbus communication protocol, install the Modbus communication driver in the power plant's data acquisition system and set the correct communication parameters (such as baud rate, data bits, stop bits, parity bits, etc.) to ensure accurate reading of voltage, frequency, and phase parameters from the power grid side.

[0079] The data acquired from the power grid monitoring equipment is verified, including data format verification (ensuring that the data meets the specified format requirements) and data range verification (checking whether parameters such as voltage, frequency, and phase are within a reasonable range). At the same time, in order to ensure the synchronization between the power grid side data and the photovoltaic power station side data, time synchronization technology (such as the NTP protocol) is used to synchronize the data acquisition equipment and the power grid monitoring equipment in the power station, so that the collected data are consistent on the time axis, which facilitates subsequent grid-connected scheduling analysis and control operations.

[0080] To further optimize the above embodiments, in step two, the process of predicting the future output power of the photovoltaic power station includes:

[0081] Calculate the output current of the photovoltaic cell using a current simulation model. The current simulation model is as follows:

[0082]

[0083] in, The output current of the photovoltaic cell is obtained through model simulation; For photocurrent, It is the reverse saturation current. The amount of electron charge. This is the current output voltage of the photovoltaic cell. For series resistance, For parallel resistors, This is the diode characteristic factor. Boltzmann's constant, The temperature of the photovoltaic cell;

[0084] Photocurrent ;in This is a proportionality coefficient, which depends on the material and structural characteristics of the photovoltaic cell. Light intensity;

[0085] Reverse saturation current ;

[0086] in, For the preset reference temperature, Reference temperature The reverse saturation current under, This refers to the bandgap width of the photovoltaic cell; all of the above are equipment parameters that can be obtained through searching.

[0087] Pre-set an initial output current of the photovoltaic cell. The value is substituted into the right side of the equation in the current simulation model, and the calculation is repeated iteratively until the result is obtained. The difference in values ​​meets the preset accuracy requirements, and then the final photovoltaic cell output current is output. ;

[0088] The series-parallel structure of photovoltaic cells corresponds to the adjustment of the output current of the photovoltaic cells. and photovoltaic cell output voltage The total photovoltaic current is obtained. and total photovoltaic voltage ;

[0089] Calculate the actual power output to the power grid This refers to the future output power of the photovoltaic power station, calculated using the following formula:

[0090]

[0091] in, This refers to the inverter conversion efficiency, which is a known parameter of the inverter equipment.

[0092] It should be noted that, regarding the proportionality coefficient For photovoltaic cells with specific materials and structures, experimental measurements can be conducted under standard test conditions, and the proportionality coefficient can be inferred by measuring the photocurrent under different light intensities. Alternatively, theoretical calculations can be performed using semiconductor physics theories and relevant photovoltaic cell models, based on the material properties of photovoltaic cells (such as the bandgap and absorption coefficient of semiconductor materials) and structural parameters (such as cell thickness and surface reflectivity). Simultaneously, professional photovoltaic cell simulation software (such as PC1D and AMPS) can be used for simulation. The material and structural parameters of the photovoltaic cell are input into the simulation software to simulate the photocurrent under different light intensities, and then the calculation is performed by reverse calculation using formulas. Meanwhile, the theoretical calculation results were compared and verified with the simulation results to further optimize the calculations. value;

[0093] for In terms of value, based on the operating characteristics of photovoltaic cells and past experience data, the initial output current of photovoltaic cells is... The value is estimated; generally, under normal light and temperature conditions, the output current of a photovoltaic cell will be within a certain range; for example, for common silicon photovoltaic cells, under standard light intensity, its output current density is approximately 30-40 mA / cm². 2 If the area of ​​the photovoltaic cell is known, a rough current value can be estimated as an initial value. Value; assuming the photovoltaic cell area is 100 square centimeters, then the initial... The value can be estimated as 3-4A.

[0094] To further optimize the above embodiments, in step three, the process of calculating and adjusting the output voltage and frequency of the photovoltaic power station inverter based on the parameters of the power grid and the photovoltaic power station, combined with the future output power, includes:

[0095] The inverter output voltage reference value is calculated using a voltage regulation model. The voltage regulation model is as follows:

[0096]

[0097] in, This is the measured value of the power grid voltage. This is the rated voltage of the power grid. This is the voltage regulation coefficient, used to consider the inverter's voltage regulation capability and the grid's tolerance to voltage fluctuations;

[0098] The inverter output frequency reference value is calculated using a frequency adjustment model. The frequency adjustment model is as follows:

[0099]

[0100] in, This is the measured value of the power grid frequency; This represents the expected output power of the photovoltaic power station, which is the rated value. This refers to the actual power output to the power grid; This is the frequency adjustment factor, used to take into account the capacity of the photovoltaic power plant, the inertia of the power grid, and the grid's tolerance to frequency fluctuations.

[0101] Adjust the inverter's output voltage and frequency to match the output voltage reference value. and output frequency reference value .

[0102] Among them, voltage adjustment coefficient The calculation formula is:

[0103]

[0104] in, and These represent the endpoints of the voltage range that the inverter can adjust at its rated output power, namely the maximum and minimum values. This represents the adjustable voltage range; This represents the power grid's specified voltage fluctuation range within the rated voltage. ± within; This represents the permissible range of grid voltage fluctuations; This is a coordination constant used to... The value range is limited to between 0.1 and 0.5;

[0105] Frequency adjustment coefficient The calculation formula is:

[0106]

[0107] in, The inertial constant of the power grid reflects its ability to resist frequency changes. The values ​​listed are for photovoltaic power plant capacity and are all within the grid's rated values.

[0108] It should be noted that if If 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 be aggravated, which in turn will cause instability of the entire photovoltaic power generation system. Since the photovoltaic power generation system is interconnected with the grid, 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, or even trigger the grid protection device to malfunction, causing the system to trip and lose power, seriously affecting the stable operation of the power system.

[0109] when If the value is too small, such as less than 0.1, although it can avoid system instability caused by excessive adjustment, it will result in the inverter's response speed to grid voltage fluctuations being too slow. When the grid voltage changes, the inverter needs a long time to adjust the output voltage to match the grid. During this period, the output voltage of the photovoltaic power station may deviate significantly from the grid voltage, affecting the grid-connected power quality. Furthermore, in the event of rapid changes in grid voltage (such as grid faults or sudden load changes), it may not be able to adjust the output voltage to the appropriate range in a timely and effective manner, leading to grid connection failure or impacting the grid. On the other hand, a value between 0.1 and 0.5 can ensure a certain adjustment speed while avoiding instability caused by excessive adjustment, thus achieving a better balance between adjustment speed and accuracy.

[0110] The inverter's own hardware characteristics and control capabilities The value of is also subject to certain limitations; the power electronic devices inside the inverter (such as IGBTs) have certain limitations on switching frequency and response speed. Values ​​outside their appropriate range may cause the inverter's control circuit to malfunction, resulting in the inability to achieve the expected voltage regulation effect; for example, excessively large values... The value may cause the inverter's control signal to exceed its maximum allowable value, resulting in the power electronics failing to switch normally and thus failing to accurately regulate the output voltage; the value range of 0.1 to 0.5 is determined based on the performance characteristics of common inverters, which can ensure that the inverter can effectively regulate the output voltage within the normal operating range, match the grid voltage, and achieve stable and efficient grid-connected operation.

[0111] To further optimize the above embodiments, in step four, the process of synchronizing the output phase of the photovoltaic power plant inverter with the grid phase using phase-locked loop technology includes:

[0112] Calculate the phase angle of the grid voltage Phase angle with the adjusted inverter output voltage error ,Right now ;

[0113] The output phase of the photovoltaic power plant inverter is synchronized with the grid phase based on a synchronization model. The synchronization model is as follows:

[0114]

[0115] in, For proportional gain, The integral gain is determined based on the response speed and accuracy requirements of phase synchronization.

[0116] By continuously adjusting the phase of the inverter's trigger pulse, the phase difference between the two is kept within a preset allowable range, ensuring that the current surge is minimized at the moment of grid connection.

[0117] It should be noted that in actual photovoltaic power station grid-connected systems, different methods are tested experimentally. and The effect of the value on the phase synchronization response speed. First, set an initial... and The value is then used to apply a simulated phase step signal (simulating a sudden phase change in the power grid) to the system, and the response curve of the inverter output phase is observed. If the response speed is too slow (e.g., the time required to reach a stable phase exceeds expectations), the value is gradually increased. Value, and adjust appropriately. The value is tested again until a value that meets the response speed requirements is found. and Value combinations. During this process, it is necessary to record the response curves under different parameter combinations for comparison and analysis.

[0118] To further optimize the above embodiment, step five also includes the initial value of the soft-start current during grid connection switching. Set to preset ratio The rated current, i.e. .

[0119] It should be noted that, for the preset ratio β, it is first necessary to conduct parameter analysis on the equipment in the photovoltaic power station (such as inverters, transformers, etc.) and the grid-side equipment (such as switchgear, cables, etc.). This involves understanding the key parameters of these devices, such as rated current and short-time withstand current. From a equipment safety perspective, the preset ratio should ensure that the current does not cause excessive impact on the equipment during the initial soft-start phase, thus guaranteeing the equipment's insulation performance and lifespan. For example, for inverters, their internal power semiconductor devices (such as IGBTs) have certain current carrying capacity limitations. According to their datasheets, the permissible 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 for the initial soft-start current value can be initially determined to be between 0.8*1.2=0.96 (i.e., 96%) and 0.8*1.5=1.2 (i.e., 120%).

[0120] To further optimize the above embodiments, in step five, grid connection switching is performed when the phase difference between the grid voltage and the photovoltaic power station output voltage is less than a first threshold and the voltage and frequency fluctuations are less than a second threshold.

[0121] It should be noted that data on voltage and frequency fluctuations during the actual operation of photovoltaic power stations, as well as relevant data during grid connection operations, are collected. Analyzing this data helps to understand the characteristics and patterns of voltage and frequency fluctuations under different operating conditions (such as different light intensities and different grid loads). Based on practical operating experience, a second threshold is determined that can both ensure stable grid operation and accommodate the normal operating changes of the photovoltaic power station. For example, statistical analysis of one year's operating data of a photovoltaic power station revealed that during normal operation, voltage fluctuations are generally within ±3% of the rated voltage, and frequency fluctuations are within ±0.1Hz. However, fluctuations may increase during special weather conditions or sudden changes in grid load. Taking these factors into consideration, the voltage fluctuation threshold is set at ±3.5% of the rated voltage, and the frequency fluctuation threshold is set at ±0.15Hz. This ensures grid stability and normal equipment operation while also taking into account the actual operating conditions of the photovoltaic power station, improving the feasibility and reliability of grid connection operations.

[0122] To further optimize the above embodiments, the method also includes: during the soft start process, the current increases according to a preset slope, that is, the rated current increases by a corresponding proportion for each sampling period until the rated current value for normal operation is reached.

[0123] It should be noted that the preset slope needs to be determined by considering the characteristics of the photovoltaic power station's output power changing with light intensity. During soft start-up, the increase in grid-connected current should match the increase in photovoltaic power station output power to achieve efficient energy conversion and stable grid-connected operation. Based on the light intensity variation patterns at the photovoltaic power station's location (e.g., gradually increasing in the morning, strongest at noon, and weakening in the evening) and the output characteristic curves of the photovoltaic cells, the rate of power change under different light intensities should be analyzed. For example, when light intensity increases slowly in the morning, the photovoltaic power station's output power also increases slowly; in this case, the preset slope can be set smaller to allow the grid-connected current to increase slowly. At noon, when light intensity is stable and strong, the power output is relatively stable, and the preset slope can be appropriately adjusted to match the stable power output. In the evening, when light intensity weakens, the power decreases, and the preset slope should also be reduced accordingly to avoid excessive current and power mismatch. Through the analysis of the relationship between light intensity and power output, a preset slope curve that varies with time and light conditions is determined to optimize the soft start-up process.

[0124] Photovoltaic power plant systems inherently possess a certain degree of inertia, including the capacitance characteristics of photovoltaic cells and the control response time of inverters. If the preset slope is too large, the photovoltaic power plant system may be unable to respond promptly to rapid changes in current, leading to control instability; conversely, if the preset slope is too small, the soft-start time will be excessively long, affecting grid connection efficiency. The preset slope is determined by balancing system response capability and soft-start efficiency through testing and analysis of the photovoltaic power plant system's inertia (such as measuring parameters like the system's time constant). For example, for systems with high inertia and long response times, the preset slope should be set smaller to ensure stable current control; for systems with low inertia and fast response times, the preset slope can be appropriately increased, but equipment and grid limitations must still be considered. Furthermore, the preset slope can be dynamically adjusted based on actual operating conditions, considering different seasons and weather conditions, to achieve optimal soft-start performance and improve the overall performance of the photovoltaic power plant.

[0125] To further optimize the above embodiments, the method also includes: providing feedback on the results after the grid connection handover is completed, and adjusting the voltage adjustment coefficient accordingly based on the handover results. and frequency adjustment coefficient Iterative optimization is then carried out.

[0126] It should be noted that after the grid connection is completed, relevant operational data of the photovoltaic power station and the power grid will be continuously collected, including but not limited to the output voltage, output current, and output power of the photovoltaic power station; the voltage, frequency, and phase of the grid side; and the magnitude of the inrush current and power quality indicators (such as harmonic content and voltage fluctuations) at the moment of grid connection and after grid connection. This data will serve as the basis for evaluating the grid connection effect and subsequent optimization and adjustment. For example, high-precision sensors installed in the photovoltaic array combiner box, inverter output terminal, and grid access point will acquire the above data in real time and transmit it to the data processing unit for storage and analysis.

[0127] Identify key indicators for evaluating grid connection performance, such as the ratio of peak grid inrush current to rated current (inrush current ratio), the fluctuation range of voltage and frequency after grid connection (e.g., the percentage of peak-to-peak voltage fluctuation to rated voltage, the percentage of maximum frequency fluctuation to rated frequency), and whether power quality indicators meet relevant standards (e.g., whether harmonic content is below the specified limit).

[0128] The actual evaluation indicators calculated from the collected data are compared with the set ideal indicators. If all evaluation indicators meet the requirements, the current grid-connected dispatch parameters (voltage adjustment coefficient and frequency adjustment coefficient) are considered appropriate and no optimization adjustment is needed for the time being. However, if any evaluation indicator fails to meet the requirements, an iterative optimization process is initiated.

[0129] The iterative optimization process is similar to the gradient descent algorithm, which will not be elaborated further.

[0130] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate 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 new energy power plants, characterized in that, include: Step 1: Collect data from the photovoltaic power station and the grid. The photovoltaic power station data includes irradiance, temperature, photovoltaic cell output voltage and current data; the grid-side data includes voltage, frequency and phase parameters. Step 2: Predict the future output power of the photovoltaic power station based on the collected data from the photovoltaic power station and the grid. Step 3: Based on the data from the photovoltaic power plant and the grid, combined with the future output power, calculate and adjust the output voltage and frequency of the photovoltaic power plant inverter to match the grid. Step 4: Based on the adjusted output voltage and frequency, use phase-locked loop technology to synchronize the output phase of the photovoltaic power station inverter with the grid phase; Step 5: After completing the voltage, frequency, and phase matching and synchronization adjustment between the photovoltaic power station and the power grid through Steps 3 and 4, the grid connection switching between the photovoltaic power station and the power grid is carried out using soft-start technology.

2. The grid-connected dispatching method for a new energy power plant according to claim 1, characterized in that, In step one, the process of collecting data from the photovoltaic power plant and the grid includes: Light intensity and temperature data are obtained by arranging light sensors and temperature sensors at different locations within the photovoltaic power station. Voltage transformers and current transformers are installed at the combiner box and inverter of the photovoltaic array to obtain the output voltage and current data of the photovoltaic cells. Voltage, frequency and phase parameters on the grid side are obtained from the grid monitoring equipment.

3. The grid-connected dispatching method for a new energy power plant according to claim 2, characterized in that, In step two, the process of predicting the future output power of the photovoltaic power station includes: Calculate the output current of the photovoltaic cell using a current simulation model. The current simulation model is as follows: in, The output current of the photovoltaic cell is obtained through model simulation; For photocurrent, It is the reverse saturation current. The amount of electron charge. This is the current output voltage of the photovoltaic cell. For series resistance, For parallel resistors, This is the diode characteristic factor. Boltzmann's constant, The temperature of the photovoltaic cell; The photogenerated current ;in This is a proportionality coefficient, which depends on the material and structural characteristics of the photovoltaic cell. Light intensity; The reverse saturation current ； in, For the preset reference temperature, Reference temperature The reverse saturation current under, The bandgap width of a photovoltaic cell; Setting the initial output current of the photovoltaic cell The value is substituted into the current simulation model, and the calculation is iteratively updated until the result obtained from two consecutive calculations is obtained. If the difference in values ​​meets the preset accuracy requirements, then the final photovoltaic cell output current will be output. ； The series-parallel structure of photovoltaic cells corresponds to the adjustment of the output current of the photovoltaic cells. and photovoltaic cell output voltage The total photovoltaic current is obtained. and total photovoltaic voltage ； Calculate the actual power output to the power grid This refers to the future output power of the photovoltaic power station, calculated using the following formula: in, This refers to the inverter conversion efficiency, which is a known parameter of the inverter equipment.

4. The grid-connected dispatching method for a new energy power plant 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 data from the photovoltaic power station and the grid, combined with future output power, includes: The inverter output voltage reference value is calculated using a voltage regulation model. The voltage regulation model is as follows: in, This is the measured value of the power grid voltage. This is the rated voltage of the power grid. This is the voltage regulation coefficient, used to consider the inverter's voltage regulation capability and the grid's tolerance to voltage fluctuations; The inverter output frequency reference value is calculated using a frequency adjustment model. The frequency adjustment model is as follows: in, This is the measured value of the power grid frequency; This represents the expected output power of the photovoltaic power station, which is the rated value. This refers to the actual power output to the power grid; This is the frequency adjustment factor, used to take into account the capacity of the photovoltaic power plant, the inertia of the power grid, and the grid's tolerance to frequency fluctuations. Adjust the inverter's output voltage and frequency to match the output voltage reference value. and output frequency reference value 。 5. A method for grid-connected dispatching of a new energy power plant according to claim 4, characterized in that, The voltage adjustment coefficient The calculation formula is: in, and These are the endpoints of the range of voltage that the inverter can regulate at its rated output power, namely the maximum and minimum values. The adjustable voltage range; The voltage fluctuation range specified for the power grid is within the rated voltage. ± Within; To allow for the range of grid voltage fluctuations; This is a coordination constant used to... The value range is limited to between 0.1 and 0.5; The frequency adjustment coefficient The calculation formula is: in, The inertial constant of the power grid reflects its ability to resist frequency changes. The values ​​listed are for photovoltaic power plant capacity and are all within the grid's rated values.

6. A method for grid-connected dispatching of a new energy power plant according to claim 5, characterized in that, In step four, the process of synchronizing the output phase of the photovoltaic power plant inverter with the grid phase using phase-locked loop technology includes: Calculate the phase angle of the grid voltage Phase angle with the adjusted inverter output voltage Error between ,Right now ； The output phase of the photovoltaic power plant inverter is synchronized with the grid phase based on a synchronization model, which is as follows: in, For proportional gain, The integral gain is determined based on the response speed and accuracy requirements of phase synchronization. By continuously adjusting the phase of the inverter's trigger pulse, the phase difference between the two is kept within a preset allowable range, ensuring that the current surge is minimized at the moment of grid connection.

7. A method for grid-connected dispatching of a new energy power plant according to claim 6, characterized in that, Step five also includes the initial value of the soft-start current during grid connection switching. Set to preset ratio The rated current, i.e. .

8. A method for grid-connected dispatching of a new energy power plant according to claim 7, characterized in that, In step five, grid connection switching is performed when the phase difference between the grid voltage and the photovoltaic power station output voltage is less than a first threshold and the voltage and frequency fluctuations are less than a second threshold.

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

10. A method for grid-connected dispatching of a new energy power plant according to claim 9, characterized in that, Also includes: After the grid connection handover is completed, the results are fed back, and the voltage adjustment coefficient is adjusted accordingly based on the handover results. and frequency adjustment coefficient Iterative optimization is then carried out.

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