New energy delivery transformer load capacity evaluation method, equipment and medium

Abstract

The invention discloses a new energy delivery transformer load capacity assessment method, equipment and a medium, which considers the volatility and uncertainty of new energy power generation, obtains output power in combination with new energy output characteristics, fully explores the load potential contained in the thermal dynamic process of a transformer by taking the thermophysical nature of the transformer as a core idea, and improves the load capacity of a new energy delivery transformer. The conservative condition that current is used as the load capacity limitation in the traditional condition is abandoned, a more accurate and deep transformer load capacity evaluation method is provided, and the load capacity of the transformer is maximized. Example results show that the evaluation method can effectively improve the load capacity of the transformer, and reference information is provided for planning and design, reliability evaluation, absorption capacity and the like of a new energy delivery power system.

Description

Technical Field

[0001] The present application relates to the technical field of transformer load assessment, and in particular to a method, device and medium for assessing the load capacity of a new energy transmission transformer. Background Art

[0002] With the rapid development of new power system construction, a large number of clean new energy sources such as wind power generation and photovoltaic power generation are widely connected to regional power grids. How to accurately evaluate the load capacity of new energy transmission transformers and achieve an economic compromise between accepting new energy and grid construction investment is a practical problem facing the power grid construction department.

[0003] There are currently two main problems with the transformer load capacity assessment method: First, in traditional cases, the transformer load capacity is constrained by life loss and is calculated under the condition of long-term operation at the highest hot spot temperature under harsh meteorological conditions such as high humidity, high temperature, and high radiation. This method essentially converts the long-term maximum allowable temperature condition into a current constraint. From the above analysis, it can be seen that the transformer maximum load capacity is based on the long-term highest hot spot temperature and conservative meteorological conditions, and the probability of such heavy-load operation and meteorological conditions occurring in reality is extremely low, which brings deviations to the transformer load capacity assessment. Second, the change of the transformer hot spot temperature lags significantly behind the current. Due to the volatility of the new energy output and the strong thermal inertia of the transformer, the short-term high-load operation of the new energy transformer does not necessarily cause excessively high operating temperatures. The traditional load capacity assessment method based on current constraints ignores the load potential during the thermal inertia process. Summary of the invention

[0004] The present application provides a method, device and medium for evaluating the load capacity of a new energy transmission transformer to solve the above-mentioned problems.

[0005] On the one hand, the present application provides a method for evaluating the load capacity of a new energy transmission transformer, the method comprising: obtaining meteorological data of a new energy power plant, and calculating the transmission current using a new energy output model; wherein new energy includes wind power generation and photovoltaic power generation; based on the transmission current, calculating the time series of the new energy transmission output current; constructing a hot spot temperature-bottom oil thermal circuit model, and calculating the bottom oil temperature solution and the hot spot temperature solution; based on the hot spot temperature curve of the transformer, judging whether the hot spot temperature reaches the temperature limit of the national standard transformer temperature rise guideline; if the temperature limit is reached, the load is too large and wind or solar power needs to be abandoned, and the capacity factor is set to ΔP, and P=P-ΔP is set, and the data of the new energy power plant after the output is abandoned is pushed into the thermal circuit model again; if the temperature limit is not reached, there is load potential, and P=P+ΔP is set, and the data of the new energy power plant after the increased load power is pushed into the thermal circuit model; repeatedly performing temperature condition cycle judgment until the hot spot temperature accuracy check θ is meths -θ limit ≤ε, the maximum power-time curve that the output transformer can carry during operation.

[0006] In one implementation of the present application, the wind farm output power time series is: P = M·p i ρ, P i is the time series of the active output power of a single wind turbine, M is the number of wind turbines, and ρ is the wake coefficient; similar to the random characteristic modeling of wind power, the output of photovoltaic cells is a random output proportional to the light intensity, and the output power of photovoltaic power per unit area is: P i =σSQ i [1-0.005(θ+25)], where: σ is the photovoltaic power conversion efficiency; S is the area of ​​the photovoltaic power source; Q se is the light intensity; θ is the ambient temperature;

[0007] The time series of the output current of new energy transmission is:

[0008]

[0009] Where: U is the bus voltage, is the power factor.

[0010] In one implementation of the present application, the temperature rise dynamic process of the transformer is divided into two heat transfer processes: ambient temperature-bottom oil temperature and bottom oil temperature-hot spot temperature. According to Kirchhoff's law, the following formula is obtained:

[0011]

[0012] Where: is the heat capacity of the bottom oil; is the thermal resistance between the bottom oil and the external environment; is the bottom oil temperature; is the iron loss; is the load loss; is the thermal capacity of the winding; is the thermal resistance between the hot spot and the bottom oil; is the hot spot temperature; is the winding loss;

[0013] The bottom oil temperature is solved as:

[0014]

[0015] In one implementation of the present application, the hot spot temperature solution is:

[0016]

[0017] Where: is the bottom oil time coefficient; is the oil viscosity; is the difference between the bottom oil temperature and the external rated temperature; η and η' are coefficients; Y l is the ratio of load loss to no-load loss; K l,t Load current percentage; P is the load loss coefficient; is the rated winding time factor; Winding loss factor; Rated temperature difference between hot spot and bottom oil.

[0018] The present application also provides a new energy transmission transformer load capacity assessment device, the device comprising:

[0019] at least one processor; and,

[0020] a memory communicatively connected to the at least one processor; wherein,

[0021] The memory stores instructions that can be executed by the at least one processor, and the instructions are executed by the at least one processor so that the at least one processor can complete the aforementioned method for evaluating the load capacity of a new energy transmission transformer.

[0022] The present application also provides a non-volatile computer storage medium for evaluating the load capacity of a new energy transmission transformer, which stores computer executable instructions. The computer executable instructions are executed by a processor to implement the aforementioned method for evaluating the load capacity of a new energy transmission transformer.

[0023] The present application provides a method, device and medium for evaluating the load capacity of a new energy transmission transformer, which takes into account the volatility and uncertainty of new energy power generation, combines the output characteristics of new energy to obtain the output power, takes the thermal physical nature of the transformer as the core idea, fully explores the load potential contained in the thermal dynamic process of the transformer, abandons the conservative condition of limiting the load capacity with current in traditional cases, and provides a more accurate and in-depth transformer load capacity evaluation method to maximize the transformer load capacity. The example results show that the evaluation method of this embodiment can effectively improve the load capacity of the transformer, and provide reference information for the planning and design of the power system, reliability evaluation and absorption capacity of new energy transmission. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The drawings described herein are used to provide a further understanding of the present application and constitute a part of the present application. The illustrative embodiments of the present application and their descriptions are used to explain the present application and do not constitute an improper limitation on the present application. In the drawings:

[0025] Figure 1A flow chart of a method for evaluating the load capacity of a new energy transmission transformer provided in an embodiment of the present application;

[0026] Figure 2 A load potential diagram under transformer temperature limit provided in an embodiment of the present application;

[0027] Figure 3 A hot spot temperature diagram of a wind power plant transmission transformer provided in an embodiment of the present application;

[0028] Figure 4 Hot spot temperature diagram under 80°C limit provided in the embodiment of the present application;

[0029] Figure 5 A schematic diagram of a new energy transmission transformer load capacity assessment device provided in an embodiment of the present application. DETAILED DESCRIPTION

[0030] In order to make the purpose, technical solution and advantages of the present application clearer, the technical solution of the present application will be clearly and completely described below in combination with the specific embodiments of the present application and the corresponding drawings. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present application.

[0031] The embodiment of the present application provides a method, device and medium for evaluating the load capacity of a new energy transmission transformer. The technical solution proposed in the embodiment of the present application is described in detail below with reference to the accompanying drawings.

[0032] Renewable energy power generation is characterized by volatility and cleanliness, rich resources and good application prospects. Combining the data of a new energy power plant and real-time meteorological environment data, the thermal circuit model is used to simulate the change process of hot spot temperature under dynamic real-time load of the transformer, and the load capacity of the transformer under temperature limit is deeply explored. The technical flow chart is as follows Figure 1 shown.

[0033] First, numerical weather forecasting technology and interpolation technology are used to obtain meteorological data of renewable energy power plants. Taking wind power generation and photovoltaic power generation as examples, the output model of renewable energy is used to calculate the external current:

[0034] According to the wind turbine power output characteristic curve, the wind turbine output is 0 below the cut-in wind speed, and the output shows a nonlinear increasing trend between the cut-in wind speed and the rated wind speed. It is in full output state between the rated wind speed and the cut-out wind speed, and the wind turbine stops when the wind speed exceeds the cut-out wind speed. Therefore, the output power (P i ) and wind speed (v i ) can be expressed as:

[0035]

[0036] Where: P i and P i，r are the actual output power and rated output power of the i-th wind turbine respectively; v i 、v i,ci 、v i,r and v i,co They are respectively the real-time wind speed, cut-in wind speed, rated wind speed and cut-out wind speed at the hub of the i-th wind turbine.

[0037] Wind energy will be weakened after passing through the upstream wind turbine, and the wind speed borne by the downstream wind turbine is significantly different from the initial state, which is called the wake effect. The wake effect is closely related to the distribution of wind turbines and the geographical environment. The monitoring data of typical wind farms show that the wake effect reduces the output to about 90% of the original. In this project, it is assumed that all wind turbines in the same wind farm are subjected to the same wind speed. Assuming that the wind farm contains M wind turbines, the active output power time series P of a single wind turbine is obtained according to the power characteristic curve of the wind turbine group. i , then the wind farm output power time series is: P i =M·p i ·ρ, where ρ is the wake coefficient.

[0038] Similar to the random characteristic modeling of wind power, the output of photovoltaic cells is a random output proportional to the light intensity. The output power of photovoltaic power per unit area is: P i =σSQ i [1-0.005(θ+25)], where: σ is the photovoltaic power conversion efficiency; S is the area of ​​the photovoltaic power source; Q se is the light intensity; θ is the ambient temperature.

[0039] The time series of the output current of new energy transmission is: Where: U is the bus voltage, is the power factor.

[0040] Furthermore, the heat generated by the transformer in actual operation is idealized as a current source, and the heat flow is equivalent to the current flow, which causes the transformer oil temperature to rise. On the one hand, the oil temperature exchanges heat with the air through the box wall and the radiator to cool down, and on the other hand, it causes losses in thermal resistance and thermal capacity. The temperature rise dynamic process of the transformer is divided into two heat transfer processes: ambient temperature-bottom oil temperature and bottom oil temperature-hot spot temperature. According to Kirchhoff's theorem, we get:

[0041]

[0042] Where: is the heat capacity of the bottom oil; is the thermal resistance between the bottom oil and the external environment; is the bottom oil temperature; is the iron loss; is the load loss; is the thermal capacity of the winding; is the thermal resistance between the hot spot and the bottom oil; is the hot spot temperature; is the winding loss.

[0043] First, the bottom oil temperature is calculated from the bottom oil-ambient temperature thermal circuit model, which is used as the hot spot temperature-ambient temperature in the bottom oil thermal circuit model, and finally the hot spot temperature is calculated.

[0044] The bottom oil temperature is solved as:

[0045]

[0046] The hot spot temperature solution is:

[0047] Where: is the bottom oil time coefficient; is the oil viscosity; is the difference between the bottom oil temperature and the external rated temperature; η and η' are coefficients; Y l is the ratio of load loss to no-load loss; K l,t Load current percentage; P is the load loss coefficient; is the rated winding time factor; Winding loss factor; Rated temperature difference between hot spot and bottom oil.

[0048] Based on the hot spot temperature curve of the transformer, determine whether the hot spot temperature reaches the temperature limit of the national standard transformer temperature rise guideline. If the temperature limit is reached, the load is too large and wind or solar power needs to be abandoned. Set the capacity factor to ΔP, set P = P-ΔP, and push the data of the new energy power plant after the abandoned output into the thermal circuit model again; if the temperature limit is not reached, there is load potential, set P = P + ΔP, and push the data of the new energy power plant after the increased load power into the thermal circuit model. Repeat the temperature condition cycle judgment until the hot spot temperature accuracy check θ is met. hs -θ limit ≤ε, the maximum power-time curve that the output transformer can carry during operation.

[0049] The following is a specific embodiment of the present application. First, the simulation is performed to simulate the change trajectory of the transformer hot spot and bottom oil temperature, explore the actual performance of the temperature significantly lagging behind the current (thermal inertia), and show that the short-term high-load operation of the new energy transformer does not necessarily cause excessive operating temperature (such as higher than the maximum long-term allowable operating temperature), thereby exploring the load potential under temperature restrictions. Secondly, using the actual example of a new energy power plant, the transformer load capacity of the power transformer under different current and hot spot temperature restrictions is explored, and the improvement effect of the transformer load nature on the load capacity is analyzed.

[0050] First, taking a single transformer as an example, assuming that the operating environment temperature is 20°C and the load is rated, the data is imported into the bottom oil temperature thermal circuit model to explore the load capacity of the transformer. The basic parameters of the transformer are shown in Table 1.

[0051] Table 1 Basic parameters of transformer

[0052]

[0053] The simulation results are as follows Figure 2 As shown in the figure, from the simulation results, it can be seen that in the initial stage of 0-90 seconds, the actual load (current) is 1.2 times, far exceeding the rated load 1 times (current) limit, and the hot spot oil temperature rises rapidly in the beginning. This is because the transformer starts in a cold start mode, the temperature is low, the oil viscosity is relatively high, the buoyancy and flow rate are small, and the heat dissipation speed is slow, which causes the hot spot temperature to rise rapidly. During this part of time, the load limit did not cause the transformer temperature to exceed the limit. The thermal inertia effect is significant, showing a huge load potential. After 90 seconds, the actual load (current) is reduced to the rated load, and the temperature will inevitably drop. At this time, the oil temperature inside the transformer is high, the oil viscosity is low, and the circulation rate is still fast. The hot spot temperature continues to rise slowly to the rated temperature of 80°C. It can be seen from the perspective of the nature of thermal load capacity that the temperature increase caused by the load limit is within the allowable range, reflecting the huge load potential.

[0054] Taking a wind farm as an example, assuming that there are 70 wind turbines and two 50MVA three-phase double-winding transformers, the load capacity of the wind farm under transformer operation is explored. The data of the wind farm is imported into the bottom oil temperature thermal circuit model. The parameters of the transformer and wind turbine within 0-1440 minutes are shown in Table 2 below. The hot spot temperature curve is shown in Figure 3 shown.

[0055] Table 2 Wind farm data table

[0056]

[0057] Depend on Figure 3It can be seen that the hot spot temperature of the transformer in the operation stage is as high as greater than 140°C. The operating load of the wind farm is too large, causing the hot spot temperature to exceed the limit that the transformer can withstand. In order to ensure the safe and reliable operation of the system, this embodiment will explore the ability to accept wind power loads under current and temperature limitations.

[0058] In this embodiment, a simulation is performed when the rated load and the rated hot spot temperature are 80°C. According to the above real-time wind power data, the time period is one minute. Figure 1 The technical flow chart calculates the real-time jettisoning power per minute, and the results are shown in Table 3 below.

[0059] Table 3 Comparison of power abandonment under different conditions

[0060]

[0061] From the data in Table 3, it can be found that although the steady-state hot spot temperature under rated load is close to 80℃, the abandoned air volume and abandoned power volume are very different, which highlights that when the transformer is traditionally limited by current, the inconsistency between current and temperature caused by the thermal inertia of the transformer is ignored, and the load potential hidden in the thermal dynamic process is not explored. The load potential of the transformer is seriously underestimated, resulting in large differences in results. Under the condition of temperature load limitation, the hot spot temperature of the transformer is as follows: Figure 4 shown.

[0062] The above is a new energy transmission transformer load capacity evaluation system provided by the embodiment of the present application. Based on the same inventive concept, the embodiment of the present application also provides a new energy transmission transformer load capacity evaluation device. Figure 5 A schematic diagram of a new energy transmission transformer load capacity assessment device provided in an embodiment of the present application, such as Figure 5 As shown, the device mainly includes: at least one processor 501; and a memory 502 that is communicatively connected to the at least one processor; wherein the memory 502 stores instructions that can be executed by the at least one processor 501, and the instructions are executed by the at least one processor 501 so that the at least one processor 501 can complete the aforementioned method for evaluating the load capacity of a new energy transmission transformer.

[0063] In addition, an embodiment of the present application also provides a non-volatile computer storage medium for evaluating the load capacity of a new energy transmission transformer, which stores computer executable instructions, and the computer executable instructions are executed by a processor to implement the aforementioned method for evaluating the load capacity of a new energy transmission transformer.

[0064] The present invention is described with reference to flowcharts and / or block diagrams of methods, devices (systems), and computer program products according to embodiments of the present invention. It should be understood that each process and / or block in the flowchart and / or block diagram, as well as the combination of processes and / or blocks in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowchart and / or block diagram. Figure 1 A process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0065] These computer program instructions may also be stored in a computer-readable memory capable of directing a computer or other programmable data processing device to operate in a specific manner, so that the instructions stored in the computer-readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1 A process or multiple processes and / or boxes Figure 1 A function specified in one or more boxes.

[0066] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operating steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing instructions for implementing the process. Figure 1 A process or multiple processes and / or boxes Figure 1 The steps for the functions specified in one or more boxes.

[0067] In a typical configuration, a computing device includes one or more processors (CPU), input / output interfaces, network interfaces, and memory.

[0068] Each embodiment in this application is described in a progressive manner, and the same or similar parts between the embodiments can be referred to each other, and each embodiment focuses on the differences from other embodiments. In particular, for the device embodiment, since it is basically similar to the method embodiment, the description is relatively simple, and the relevant parts can be referred to the partial description of the method embodiment.

[0069] It should also be noted that the terms "include", "comprises" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, commodity or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, commodity or device. In the absence of more restrictions, the elements defined by the sentence "comprises a ..." do not exclude the existence of other identical elements in the process, method, commodity or device including the elements.

[0070] The above is only an embodiment of the present application and is not intended to limit the present application. For those skilled in the art, the present application may have various changes and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application should be included in the scope of the claims of the present application.

Claims

1. A method for evaluating the load capacity of a new energy transmission transformer, characterized in that: The method comprises: obtaining meteorological data of a new energy power plant, and calculating an external transmission current using a new energy output model; wherein new energy includes wind power generation and photovoltaic power generation; based on the external transmission current, calculating a time series of an external transmission output current of new energy; constructing a hot spot temperature-bottom oil thermal circuit model, and calculating a bottom oil temperature solution and a hot spot temperature solution; judging whether the hot spot temperature reaches the temperature limit of the national standard transformer temperature rise guideline based on the hot spot temperature curve of the transformer; if the temperature limit is reached, the load is too large and wind or solar power needs to be abandoned, and the capacity factor is set to ΔP, and P=P-ΔP is set, and the data of the new energy power plant after the output is abandoned is pushed into the thermal circuit model again; if the temperature limit is not reached, there is a load potential, and P=P+ΔP is set, and the data of the new energy power plant after the increased load power is pushed into the thermal circuit model; and the temperature condition cycle judgment is repeated until the hot spot temperature accuracy check θ is met. hs -θ limit ≤ε, the maximum power-time curve that the output transformer can carry during operation.

2. A method for evaluating the load capacity of a new energy transmission transformer according to claim 1, characterized in that: The wind farm output power time series is: P = M·p i ρ, P i is the time series of the active output power of a single wind turbine, M is the number of wind turbines, and ρ is the wake coefficient; the output of the photovoltaic cell is a random output proportional to the light intensity, and the output power of the photovoltaic power source per unit area is: P i =σSQ i [1-0.005(θ+25)] Where: σ is the photovoltaic power conversion efficiency; S is the area of ​​the photovoltaic power source; Q se is the light intensity; θ is the ambient temperature; The time series of the output current of new energy transmission is: Where: U is the bus voltage, is the power factor.

3. A method for evaluating the load capacity of a new energy transmission transformer according to claim 1, characterized in that: The temperature rise dynamic process of the transformer is divided into two heat transfer processes: ambient temperature-bottom oil temperature and bottom oil temperature-hot spot temperature. According to Kirchhoff's law, the following formula is obtained: Where: is the heat capacity of the bottom oil; is the thermal resistance between the bottom oil and the external environment; is the bottom oil temperature; is the iron loss; is the load loss; is the thermal capacity of the winding; is the thermal resistance between the hot spot and the bottom oil; is the hot spot temperature; is the winding loss; Among them, the bottom oil temperature is solved as:

4. A method for evaluating the load capacity of a new energy transmission transformer according to claim 1, characterized in that: The hot spot temperature solution is: Where: is the bottom oil time coefficient; is the oil viscosity; is the difference between the bottom oil temperature and the external rated temperature; η and η' are coefficients; Y l is the ratio of load loss to no-load loss; K l,t Load current percentage; P is the load loss coefficient; is the rated winding time factor; Winding loss factor; Rated temperature difference between hot spot and bottom oil.

5. A new energy transmission transformer load capacity assessment device, characterized in that: The device comprises: at least one processor; and, a memory communicatively connected to the at least one processor; wherein, The memory stores instructions that can be executed by the at least one processor, and the instructions are executed by the at least one processor so that the at least one processor can complete the method for evaluating the load capacity of a new energy transmission transformer as described in any one of claims 1-4.

6. A non-volatile computer storage medium for evaluating the load capacity of a new energy transmission transformer, storing computer executable instructions, characterized in that: The computer executable instructions are executed by a processor to implement a method for evaluating the load capacity of a new energy transmission transformer as described in any one of claims 1 to 4.

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