A method for calculating the maximum load loss hours of photovoltaic power station collector lines

Abstract

The present invention discloses a method for calculating the maximum load loss hours of a photovoltaic power station's collector circuit, relating to the technical field of photovoltaic power stations. Based on the half-sine theory of global solar radiation, the method sets the photovoltaic power station's annual average maximum output coefficient α and the annual average power loss coefficient θ caused by factors such as weather to solar radiation, establishing a photovoltaic approximate output model. Based on the annual photovoltaic power generation and the AC-side installed capacity, the equivalent utilization hours #imgabs0# on the AC side are determined. Based on the correlation formula between the AC-side equivalent utilization hours #imgabs1# and the photovoltaic power generation and the approximate output model, the product of the coefficients α and θ is determined. Based on the annual available sunshine hours T and the product of the coefficients α and θ, the maximum load loss hours τ are determined. The present invention comprehensively considers the random influence of factors such as weather to establish a photovoltaic approximate output model, enabling a relatively accurate estimation of the maximum load loss hours of the collector circuit, thereby resolving the problem of excessive deviation in calculations based on lookup tables in power system manuals.

Description

Technical Field

[0001] The present invention relates to the technical field of photovoltaic power station line loss, in particular to a method for calculating the maximum load loss hours of a photovoltaic power station collector line. Background Art

[0002] Photovoltaic power plants utilize a large amount of cable for collector lines, and their losses are a significant component of their power losses. In the era of grid parity for renewable energy projects, reducing the cost per kilowatt-hour (KWh) is increasingly crucial. Therefore, collector line cables should be selected based on their economic cross-section. Determining this economic cross-section requires calculating the economic current density, and the number of hours of maximum load loss is a key parameter influencing this. However, to date, there is no method for calculating the maximum load loss hours for collector lines in photovoltaic power plants. Previously, values were obtained by referring to tables in power system manuals based on maximum load utilization hours and power factor. However, the load characteristics of power systems differ significantly from those of photovoltaic output, and this method can lead to significant errors in the calculated results.

[0003] Therefore, a method for calculating the maximum load loss hours of the photovoltaic power station collection line is proposed. Summary of the Invention

[0004] The purpose of the present invention is to propose a method for calculating the maximum load loss hours of the collector line of a photovoltaic power station. According to the photovoltaic output characteristics, the maximum load loss hours of the collector line are calculated to solve the problem of large calculation deviation when referring to the table in the power system manual.

[0005] The technical solution adopted in the present invention is as follows:

[0006] The present invention provides a method for calculating the maximum load loss hours of a photovoltaic power station collector line, comprising the following steps:

[0007] Based on the half-sine theory of global solar radiation, the annual average maximum output coefficient α of the photovoltaic power station and the annual average power loss coefficient θ caused by weather and other factors to solar radiation are set, and an approximate photovoltaic output model based on the coefficients α and θ is established;

[0008] Based on the photovoltaic approximate output model, a correlation formula between the photovoltaic annual power generation W and the coefficients α and θ is established;

[0009] Determine the equivalent utilization hours of the AC side based on the annual photovoltaic power generation W and the AC side installed capacity

[0010] Based on equivalent utilization hours on the AC side and the correlation formula between photovoltaic power generation and approximate output model, and determine the product of coefficients α and θ;

[0011] Based on the annual available sunlight hours T and the product of coefficients α and θ, the maximum load loss hours τ is determined. The specific calculation formula is:

[0012]

[0013] Where τ is the maximum load loss hours, is the equivalent utilization hours of the AC side of the photovoltaic power station, T is the annual sunshine hours, and C is a constant.

[0014] Furthermore, based on the half-sine theory of total solar radiation, the photovoltaic approximate output model is established as follows:

[0015]

[0016] Where P is the output of the photovoltaic power station; α is the annual average maximum output coefficient of the photovoltaic power station; θ is the annual average power loss coefficient caused by weather and other factors to solar radiation; T i P is the number of hours of sunlight per day; max is the AC side capacity of the photovoltaic power station.

[0017] Furthermore, the half-sine theory of total solar radiation states that the hourly change in solar radiation intensity is close to a half-sine curve. The half-sine model formula of total solar radiation is as follows:

[0018]

[0019] Among them, Q τ (t) is the total solar radiation value at a certain moment, a and b are the sunrise and sunset times respectively, A Q It is the hourly maximum value of total daily radiation. The solar radiation intensity is proportional to the approximate photovoltaic output.

[0020] Furthermore, a correlation formula between the annual power generation W and the coefficients α and θ is established.

[0021]

[0022] According to the equivalent utilization hours of the AC side And the correlation formula between the annual power generation W and the coefficients α and θ, determine the product of the coefficients α and θ,

[0023] From formula 4, we can get:

[0024]

[0025] in, It is the equivalent utilization hours of the AC side of the photovoltaic power station.

[0026] Furthermore, the equivalent utilization hours of the AC side of the photovoltaic power station

[0027] Furthermore, when the power delivered by the collector line always maintains the maximum power S max , the energy loss in τ hours is exactly equal to the actual loss throughout the year, then τ is called the maximum load loss hours, and its formula is:

[0028]

[0029] Based on the formula for calculating the maximum load loss hours and the characteristics that the inverter output voltage is basically constant and the power factor is close to 1 when the photovoltaic power station is running, it is concluded that:

[0030]

[0031] Furthermore, based on the maximum load loss hours and the photovoltaic approximate output model, the formula for the maximum load loss hours is determined:

[0032]

[0033] Finally, from formula 9, we can get:

[0034]

[0035] Substituting the product of α and θ, Formula 5, into Formula 10, we obtain the final formula for calculating the maximum load loss hours:

[0036]

[0037] In formula 1, the value of constant C is 0.81, and T is the number of hours of sunshine per year.

[0038] In summary, due to the adoption of the above technical solution, the beneficial effects of the present invention are:

[0039] 1. The present invention is a method for calculating the maximum load loss hours of the collector line of a photovoltaic power station. It uses the semi-sine theory of total solar radiation, comprehensively considers the random influence caused by factors such as weather, and establishes a photovoltaic approximate output model. It can accurately estimate the maximum load loss hours of the collector line, solving the problem that there is currently no method for calculating the maximum load loss hours of the collector line of a photovoltaic power station, and the error in the value obtained by looking up the table in the relevant manual of the power system is large. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for use in the embodiments. It should be understood that the following drawings only illustrate certain embodiments of the present invention and should not be considered as limiting the scope. A person of ordinary skill in the art can also derive other relevant drawings based on these drawings without inventive effort, among which:

[0041] Figure 1 It is a curve diagram of the hourly solar radiation intensity change in the present invention. DETAILED DESCRIPTION

[0042] In order to make the objectives, technical solutions, and advantages of the present invention more clearly understood, the present invention is further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only intended to explain the present invention and are not intended to limit the present invention. That is, the embodiments described herein are only some embodiments of the present invention, not all embodiments. Generally, the components of the embodiments of the present invention described and illustrated in the drawings herein may be arranged and designed in various different configurations.

[0043] It should be noted that the terms "comprises", "includes" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, article or apparatus that includes a series of elements includes not only those elements, but also includes other elements not explicitly listed, or also includes elements that are inherent to such process, method, article or apparatus.

[0044] It should be understood that the terms "up", "down", "left", "right", etc., indicating directions or positional relationships, are based on the directions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific direction, be constructed and operated in a specific direction. Therefore, it should not be understood as a limitation on the present invention.

[0045] The features and performance of the present invention are further described in detail below with reference to the embodiments.

[0046] Example 1

[0047] A method for calculating the maximum load loss hours of a photovoltaic power station collector line comprises the following steps:

[0048] Based on the half-sine theory of global solar radiation, the annual average maximum output coefficient α of the photovoltaic power station and the annual average power loss coefficient θ caused by weather and other factors to solar radiation are set, and an approximate photovoltaic output model based on the coefficients α and θ is established;

[0049] Based on the photovoltaic approximate output model, a correlation formula between the photovoltaic annual power generation W and the coefficients α and θ is established;

[0050] Determine the equivalent utilization hours of the AC side based on the annual photovoltaic power generation W and the AC side installed capacity

[0051] Based on equivalent utilization hours on the AC side and the correlation formula between photovoltaic power generation and approximate output model, and determine the product of coefficients α and θ;

[0052] Based on the annual available sunlight hours T and the product of coefficients α and θ, the maximum load loss hours τ is determined. The specific calculation formula is:

[0053]

[0054] Where τ is the maximum load loss hours, is the equivalent utilization hours of the AC side of the photovoltaic power station, T is the annual sunshine hours, and C is a constant.

[0055] Furthermore, based on the half-sine theory of total solar radiation, the photovoltaic approximate output model is established as follows:

[0056]

[0057] Where P is the output of the photovoltaic power station; α is the annual average maximum output coefficient of the photovoltaic power station; θ is the annual average power loss coefficient caused by weather and other factors to solar radiation; T i P is the number of hours of sunlight per day; max is the AC side capacity of the photovoltaic power station.

[0058] Furthermore, the half-sine theory of total solar radiation states that the hourly change in solar radiation intensity is close to a half-sine curve. The half-sine model formula of total solar radiation is as follows:

[0059]

[0060] Among them, Q τ (t) is the total solar radiation value at a certain moment, a and b are the sunrise and sunset times respectively, A Q It is the hourly maximum value of total daily radiation. The solar radiation intensity is proportional to the approximate photovoltaic output.

[0061] Furthermore, a correlation formula between the annual power generation W and the coefficients α and θ is established.

[0062]

[0063] According to the equivalent utilization hours of the AC side And the correlation formula between the annual power generation W and the coefficients α and θ, determine the product of the coefficients α and θ,

[0064] From formula 4, we can get:

[0065]

[0066] in, It is the equivalent utilization hours of the AC side of the photovoltaic power station.

[0067] Furthermore, the equivalent utilization hours of the AC side of the photovoltaic power station

[0068] Furthermore, when the power delivered by the collector line always maintains the maximum power S max , the energy loss in τ hours is exactly equal to the actual loss throughout the year, then τ is called the maximum load loss hours, and its formula is:

[0069]

[0070] Based on the formula for calculating the maximum load loss hours and the characteristics that the inverter output voltage is basically constant and the power factor is close to 1 when the photovoltaic power station is running, it is concluded that:

[0071]

[0072] Furthermore, based on the maximum load loss hours and the photovoltaic approximate output model, the formula for the maximum load loss hours is determined:

[0073]

[0074] Finally, from formula 9, we can get:

[0075]

[0076] Substituting the product of α and θ, Formula 5, into Formula 10, we obtain the final formula for calculating the maximum load loss hours:

[0077]

[0078] In formula 1, the value of constant C is 0.81, and T is the number of hours of sunshine per year.

[0079] At present, the maximum load loss hours of transmission and distribution lines in power systems are mostly calculated by table lookup method. However, the calculation method based on the power system does not conform to the output characteristics of photovoltaics, and the calculation results cannot reflect the actual situation. There is no calculation method for the maximum load loss hours of the collection lines of photovoltaic power stations. The present invention uses the semi-sine theory of total solar radiation and comprehensively considers the random influence caused by factors such as weather to establish a photovoltaic approximate output model. It can more accurately estimate the maximum load loss hours of the collection lines, solving the problem of large errors in the values obtained by table lookup based on the relevant manuals of the power system.

[0080] The above description is merely a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be conceived by a person skilled in the art within the technical scope disclosed by the present invention without inventive effort should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be based on the scope of protection defined in the claims.

Claims

1. A method for calculating the maximum load loss hours of a photovoltaic power station collector line, characterized in that: The following steps are involved: According to the half-sine theory of total solar radiation, the annual maximum output coefficient of the photovoltaic power station is set The average annual power loss coefficient of solar radiation caused by weather factors , establish the coefficient and Photovoltaic approximate output model; Based on the photovoltaic approximate output model, the photovoltaic annual power generation W and coefficient and The correlation formula of Determine the equivalent utilization hours of the AC side based on the annual photovoltaic power generation W and the AC side installed capacity ; Based on equivalent utilization hours on the AC side And the correlation formula between photovoltaic power generation and approximate output model, determine the coefficient and The product of Based on the annual sunshine hours T and coefficient and The product of the maximum load loss hours is determined , the specific calculation formula is: （1） in, is the maximum load loss hours, is the equivalent utilization hours of the AC side of the photovoltaic power station, and T is the annual sunshine hours.

2. The method for calculating the maximum load loss hours of a photovoltaic power station collector line according to claim 1, characterized in that: Based on the half-sine theory of global solar radiation, the photovoltaic approximate output model is established as follows: （2） Wherein, P is the output of the photovoltaic power station; is the annual maximum output coefficient of the photovoltaic power station; is the annual average power loss coefficient of solar radiation caused by weather factors; The number of hours of sunlight per day; is the AC side capacity of the photovoltaic power station.

3. The method for calculating the maximum load loss hours of a photovoltaic power station collector line according to claim 2, characterized in that: The half-sine theory of global solar radiation states that the hourly change in solar radiation intensity is close to a half-sine curve. The half-sine model formula for global solar radiation is as follows: （3） in, is the total solar radiation value at a certain moment, a and b are the sunrise and sunset times respectively, It is the hourly maximum value of total daily radiation. The solar radiation intensity is proportional to the approximate photovoltaic output.

4. The method for calculating the maximum load loss hours of a photovoltaic power station collector line according to claim 2, characterized in that: Establish the annual power generation W and coefficient and The correlation formula, （4） According to the equivalent utilization hours of the AC side And the annual power generation W and coefficient and The correlation formula, determination coefficient and The product of From formula (4), we can get: （5） in, It is the equivalent utilization hours of the AC side of the photovoltaic power station.

5. The method for calculating the maximum load loss hours of a photovoltaic power station collector line according to claim 4, characterized in that: Equivalent utilization hours of the AC side of the photovoltaic power station (6).

6. The method for calculating the maximum load loss hours of a photovoltaic power station collector line according to claim 5, characterized in that: Based on the maximum load loss hours and the photovoltaic approximate output model, the formula for determining the maximum load loss hours is: （9） Finally, formula (9) yields: （10） The formula and Substituting the product formula (5) into formula (10) yields the final calculation formula for the maximum load loss hours.

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