Photovoltaic bearing capacity measuring and calculating method considering dynamic current-carrying capacity of line

Abstract

The invention discloses a photovoltaic bearing capacity measuring and calculating method considering the dynamic current-carrying capacity of a line. The method comprises the steps that dynamic meteorological data of a region where a current-carrying capacity calculation selected feeder line is located and basic parameters of the line are acquired and sorted; acquiring operation data; calculating the steady-state current-carrying capacity of the line and the transient current-carrying capacity of which the remaining time is 60 minutes; setting a line safety operation constraint which needs to be met for calculating the line safety constraint photovoltaic bearing capacity; calculating the line safety constraint photovoltaic bearing capacity meeting the line safety operation constraint condition by using a binary cyclic approximation method; and calculating the photovoltaic bearing capacity meeting the line electric power and electric quantity balance based on the feeder line operation data, and calculating the line photovoltaic bearing capacity. The method has the beneficial effects that the line current-carrying capacity under the dynamic meteorological data is calculated, and the line photovoltaic bearing capacity meeting the safety constraint is calculated based on the line dynamic current-carrying capacity, so that the photovoltaic bearing capacity maximizing the line utilization rate is obtained; and the distributed photovoltaic system can be more efficiently merged into the power distribution network under the condition of satisfying safe operation.

Description

Technical Field

[0001] The present invention relates to a method for calculating the photovoltaic carrying capacity, specifically a method for calculating the photovoltaic carrying capacity considering the dynamic current-carrying capacity of the line, and belongs to the technical field of power system optimization planning. Background Art

[0002] With the rapid development of distributed photovoltaics, how to accurately calculate the photovoltaic carrying capacity of distribution lines has become one of the key challenges to ensure the safe grid connection of distributed photovoltaics. This is not only related to the safety and stability of power grid operation, but also an important prerequisite for improving the access efficiency of photovoltaic power generation and promoting the wider application of clean energy.

[0003] In the prior art, such as a method for evaluating the distributed photovoltaic carrying capacity based on voltage sensitivity ranking disclosed in the patent with publication number CN114243778A, which includes: constructing a distribution network structure with a high proportion of distributed photovoltaics, constructing an evaluation index for the distributed photovoltaic acceptance capacity of the distribution network, and evaluating the distributed photovoltaic carrying capacity of the distribution network based on voltage sensitivity ranking. It has fast calculation speed and significant convergence effect. Based on the constructed voltage deviation evaluation index and voltage sensitivity ranking, it can quickly find the photovoltaic access scheme under the limit carrying capacity of the distribution network. However, currently, the calculation methods for distributed photovoltaic carrying capacity usually calculate based on the safe current-carrying capacity of the line under fixed meteorological conditions. The meteorological conditions considered in the safe current-carrying capacity under fixed meteorological conditions are generally extreme meteorological conditions, that is, the transmission capacity limit of the line will undergo multiple "safety" checks according to the worst conditions during the design, operation, and dispatch processes. This results in the actual line transmission capacity being generally controlled at a relatively low level. Therefore, although there is potential for higher transmission capacity, the current practice fails to fully utilize the line resources, thus causing hidden waste of photovoltaic carrying capacity. Aiming at the problem of hidden waste of transmission capacity in the above-mentioned distribution line transmission limit, this application proposes a method for calculating the photovoltaic carrying capacity of the line considering the current-carrying capacity under dynamic meteorological conditions. Summary of the Invention

[0004] The purpose of the present invention is to propose a method for calculating the photovoltaic carrying capacity of the line considering the current-carrying capacity under dynamic meteorological conditions. On the one hand, aiming at the problem of hidden waste of transmission capacity generally existing in the actual line transmission capacity, considering the dynamic meteorological conditions to calculate the line current-carrying capacity, aiming to maximize the line transmission capacity; on the other hand, to ensure the efficient and safe grid connection of distributed photovoltaics.

[0005] The present invention realizes the above purpose through the following technical solutions: A method for calculating the photovoltaic carrying capacity considering the dynamic current-carrying capacity of the line, including the following steps:

[0006] S1. Obtain and organize the dynamic meteorological data and line basic parameters of the feeder selected for current-carrying capacity calculation in the region.

[0007] S2. Obtain the operation data required for the calculation of the 10kV feeder for which the PV carrying capacity needs to be calculated.

[0008] S3. Calculate the steady-state current-carrying capacity of the line and the transient current-carrying capacity with a remaining time of 60 minutes based on the dynamic meteorological data and line basic parameters.

[0009] S4. Set the line safety operation constraints that need to be satisfied for calculating the PV carrying capacity with line safety constraints.

[0010] S5. Use the binary cyclic approximation method to calculate the PV carrying capacity with line safety constraints that satisfies the line safety operation constraints.

[0011] S6. Calculate the PV carrying capacity that satisfies the line power and energy balance based on the feeder operation data, and calculate the PV carrying capacity of the line under dynamic changing meteorological conditions.

[0012] As a further solution of the present invention: obtaining and organizing the dynamic meteorological data and the line basic parameters required for current-carrying capacity calculation includes: the sunshine intensity, ambient temperature, and wind speed in the region where the feeder is located in the past three years. After detailed analysis and organization of the meteorological data in the past three years, select the meteorological condition data of the day with the lowest current-carrying capacity as the basic meteorological input data for subsequent calculations; obtain and organize the parameters of the conductor used in the feeder, including: specific model, wiring form, safety current, conductor outer diameter, Steele coefficient, resistance temperature coefficient, AC / DC resistance ratio, DC resistance value at 20°C, skin effect coefficient, insulation heat absorption coefficient, insulation heat transfer coefficient, insulation radiation coefficient, mass per unit length, specific heat capacity, and maximum allowable temperature of the line.

[0013] As a further solution of the present invention: obtaining the operation data required for the calculation of the 10kV feeder for which the PV carrying capacity needs to be calculated includes: the active power of the load of the 10kV feeder for 20 hours on the selected day, and the existing PV output curve of the feeder.

[0014] As a further solution of the present invention: the specific method for calculating the steady-state current-carrying capacity of the line and the transient current-carrying capacity with a remaining time of 60 minutes based on the dynamic meteorological data and line basic parameters is as follows:

[0015] The calculation of the steady-state current-carrying capacity of the line based on the dynamic meteorological data is shown in the following formula:

[0016]

[0017] In the formula, I1 is the steady-state current-carrying capacity of the line (A), R acR(t) represents the AC resistance (Ω / m) at wire temperature t, P r represents the radiation power (W / m), P c represents the convective power of the wire (W / m), P s represents the solar heat absorption power of the wire (W / m);

[0018] Among them, the AC resistance R ac (t) at wire temperature t is calculated as follows:

[0019]

[0020] In the formula, I is the skin effect coefficient of the wire, and β is the ratio of AC to DC resistance of the wire; R dc is the DC resistance of the conductor at 20°C, t d is the conductor temperature (°C), α 20 is the resistance temperature coefficient of the conductor at 20°C;

[0021] Among them, the radiation power P r is calculated as follows:

[0022]

[0023] In the formula, ε is the radiation coefficient of the outer surface insulation layer of the wire, S is the Stefan-Boltzmann constant; D is the outer diameter of the wire (m), t d is the conductor temperature (°C), T c is the ambient temperature (°C);

[0024] Among them, the convective heat dissipation power P c is calculated as follows:

[0025]

[0026] In the formula, λ is the heat transfer coefficient of the outer insulation layer of the wire (W·m -1 ·K -1 )), θ is the current-carrying temperature rise of the conductor (°C), R e is the Reynolds number;

[0027] The calculation method of the current-carrying temperature rise θ of the conductor is as follows:

[0028] θ = t d - T c

[0029] The Reynolds number R e is calculated as follows:

[0030] R e = νD / ν f

[0031] Wherein, v is the wind speed (m / s), D is the outer diameter of the wire (m), and v f is the aerodynamic viscosity;

[0032] The aerodynamic viscosity v f is calculated as follows:

[0033] ν f = 1.32×10 -5 + 9.6(T c + θ / 2)×10 -5

[0034] Wherein, T c is the ambient temperature (°C), and θ is the current-carrying temperature rise of the conductor (°C);

[0035] Among them, the heat P s generated by the conductor's solar radiation heat absorption is calculated as follows:

[0036] P s = γDS i

[0037] Wherein, γ is the heat absorption coefficient of the insulated wire surface, S i is the solar radiation intensity (W / m 2 ), and D is the outer diameter of the wire (m);

[0038] Based on the dynamic meteorological data, the transient current-carrying capacity of the line with a remaining time of Δt = 60 min is calculated as follows:

[0039] Wherein, I2 is the transient current-carrying capacity of the line (A), R ac (t) represents the AC resistance (Ω / m) at the conductor temperature t, P r represents the radiation power, P c represents the convective power of the wire, P s represents the solar radiation heat absorption power of the wire (W / m), C p is the heat capacity coefficient of the wire (J / kg·°C), m is the mass per unit length of the wire (kg / m), t d is the conductor temperature (°C), T max represents the maximum operating temperature of the wire (°C), which is selected according to the GB 50545-2010 standard, Δt is the remaining time (min), and ΔT s is the temperature difference between the conductor temperature and the maximum allowable temperature (°C).

[0040] As a further solution of the present invention: The line safety operation constraints that need to be satisfied for setting the line safety constraint photovoltaic bearing capacity are as follows:

[0041]

[0042] In the formula: ΔP0 is the photovoltaic carrying capacity of the line under safety constraints (kW), I2 is the transient current-carrying capacity of the line (A), U N is the rated voltage of the line (kV), I1 is the steady-state current-carrying capacity of the line (A), ΔP t is the 24-hour active power of the increasing photovoltaic power of the line (kW), t is the time (min), η is the photovoltaic output curve of the line, T Δ is for ΔP t The duration (min) when it is > P1.

[0043] As a further solution of the present invention: The dichotomy loop approximation method is used to calculate the photovoltaic carrying capacity of the line under safety constraints that meets the line safety operation constraint conditions.

[0044] As a further solution of the present invention: Based on the feeder operation data, calculate the photovoltaic carrying capacity of the line for power and electricity balance, and calculate the photovoltaic carrying capacity of the line under dynamically changing meteorological conditions. The calculation process is as follows:

[0045] Based on the feeder operation data, calculate the photovoltaic carrying capacity of the line that meets the power and electricity balance of the line as follows:

[0046] p g1 = min(p L,t - p pv,t )

[0047] In the formula: P g1 is the current photovoltaic carrying capacity of the line (kW), P L,t is the active power of the typical daily load of the line, t is the time, P pv,t is the active power of the photovoltaic output already connected to the line;

[0048] The calculation of the photovoltaic carrying capacity of the line considering the current-carrying capacity of the line under dynamically changing meteorological conditions is as follows:

[0049] p g = △p0 × μ + p g1

[0050] In the formula: P g is the photovoltaic carrying capacity of the line (kW), Δp0 is the photovoltaic carrying capacity of the line under safety constraints calculated in step (5) (kW), μ is the percentage of the line safety capacity, and the value of μ is selected according to the line wiring form, P g1 is the photovoltaic carrying capacity of the line that meets the power and electricity balance of the line (kW).

[0051] The beneficial effects of the present invention are as follows: By collecting the meteorological data of the area where the selected feeder is located, the wire data used by the feeder, and the operating parameters of the feeder, the present invention can ultimately obtain the line photovoltaic carrying capacity considering the dynamic meteorological download current, calculate the line current-carrying capacity under dynamic meteorological data, and calculate the line photovoltaic carrying capacity that meets the safety constraints based on the line dynamic current-carrying capacity, so as to obtain the photovoltaic carrying capacity that maximizes the line utilization rate, and promote the more efficient integration of distributed photovoltaics into the distribution network under the condition of meeting safe operation. BRIEF DESCRIPTION OF THE DRAWINGS

[0052] Figure 1 It is a schematic diagram of the method steps of the present invention;

[0053] Figure 2 It is a schematic diagram of the meteorological condition data on the day with the lowest current-carrying capacity of the present invention;

[0054] Figure 3 It is a schematic diagram of the conductor temperature data on the day with the lowest current-carrying capacity of the present invention;

[0055] Figure 4 It is a schematic diagram of the steady-state current-carrying capacity of the selected feeder of the present invention and the transient current-carrying capacity with a remaining time of 60 minutes;

[0056] Figure 5 It is a schematic diagram of the typical daily load curve of the present invention;

[0057] Figure 6 It is a schematic diagram of the photovoltaic output characteristic curve of the area where the feeder of the present invention is located;

[0058] Figure 7 It is a schematic diagram of the calculation process of the line constraint photovoltaic carrying capacity of the present invention;

[0059] Figure 8 It is a derivation diagram of the transient current-carrying capacity calculation formula of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0060] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0061] Embodiment 1, as Figure 1 shown, a method for measuring the photovoltaic carrying capacity considering the line dynamic current-carrying capacity includes the following steps:

[0062] S1. Obtain and sort out the dynamic meteorological data and line basic parameters of the area where the selected feeder for current-carrying capacity calculation is located;

[0063] S2. Obtain the operation data required for the calculation of the 10kV feeder for photovoltaic carrying capacity calculation;

[0064] S3. Calculate the steady-state current-carrying capacity of the line and the transient current-carrying capacity with a remaining time of 60 minutes based on the dynamic meteorological data and line basic parameters;

[0065] S4. Set the line safe operation constraints that need to be satisfied for calculating the line safety constraint photovoltaic carrying capacity;

[0066] S5. Use the binary cyclic approximation method to calculate the line safety constraint photovoltaic carrying capacity that meets the line safe operation constraint conditions;

[0067] S6. Calculate the photovoltaic carrying capacity that meets the line power and electricity balance based on the feeder operation data, and calculate the line photovoltaic carrying capacity under dynamic changing meteorological conditions.

[0068] Embodiment 2. In addition to including all the technical features in Embodiment 1, this embodiment further includes: obtaining and sorting out the dynamic meteorological data and the line basic parameters required for current-carrying capacity calculation, including: the solar radiation intensity, ambient temperature and wind speed in the area where the feeder is located in the past three years. After detailed analysis and sorting of the meteorological data in the past three years, select the meteorological condition data of the day with the lowest current-carrying capacity as the basic meteorological input data for subsequent calculations; obtain and sort out the parameters of the conductor used by the feeder, including: specific model, wiring form, safe current, conductor outer diameter, Steele coefficient, resistance temperature coefficient, AC / DC resistance ratio, DC resistance value at 20°C, skin effect coefficient, insulation heat absorption coefficient, insulation heat transfer coefficient, insulation radiation coefficient, mass per unit length, specific heat capacity and heat released per unit temperature change.

[0069] The operation data required for the calculation of the 10kV feeder for photovoltaic carrying capacity calculation includes: the active power of the 10kV feeder for 20 hours on the selected day, and the existing photovoltaic output curve of the feeder.

[0070] The specific method for calculating the steady-state current-carrying capacity of the line and the transient current-carrying capacity with a remaining time of 60 minutes based on the dynamic meteorological data and line basic parameters is as follows:

[0071] The calculation of the steady-state current-carrying capacity of the line based on the dynamic meteorological data is shown in the following formula:

[0072]

[0073] In the formula, I1 is the steady-state current-carrying capacity of the line (A), and R ac (t) represents the AC resistance (Ω / m) at the conductor temperature t, P r represents the radiation power, P c represents the convective power of the conductor, Ps Represents the solar heat absorption power of the conductor (W / m);

[0074] Among them, the AC resistance R of the conductor at temperature t of the conductor ac (t) The calculation method is as shown in the following formula:

[0075]

[0076] In the formula, I is the skin effect coefficient of the conductor, β is the ratio of the AC and DC resistances of the conductor; R dc is the DC resistance of the conductor at 20°C, t d is the conductor temperature (°C), α 20 is the resistance temperature coefficient of the conductor at 20°C;

[0077] Among them, the radiation power P r The calculation method is as shown in the following formula:

[0078]

[0079] In the formula, ε is the radiation coefficient of the outer surface insulation layer of the conductor, S is the Stefan-Boltzmann constant; D is the outer diameter of the conductor (m), t d is the conductor temperature (°C), T c is the ambient temperature (°C);

[0080] Among them, the convective heat dissipation power P c The calculation method is as shown in the following formula:

[0081]

[0082] In the formula, λ is the heat transfer coefficient of the outer insulation layer of the conductor (W·m -1 ·K -1 ), θ is the current-carrying temperature rise of the conductor (°C), R e is the Reynolds number;

[0083] The calculation method of the current-carrying temperature rise θ of the conductor is as follows:

[0084] θ = t d -T c

[0085] The Reynolds number R e The calculation method is as shown in the following formula:

[0086] R e = νD / ν f

[0087] In the formula, v is the wind speed (m / s), D is the outer diameter of the conductor (m), v f is the kinematic viscosity of air;

[0088] The kinematic viscosity v of airf The calculation method is shown in the following formula:

[0089] ν f = 1.32×10 -5 + 9.6(T c + θ / 2)×10 -5

[0090] In the formula, T c is the ambient temperature (°C), and θ is the current-carrying temperature rise of the conductor (°C);

[0091] Among them, the heat P s generated by the conductor absorbing heat from sunlight is calculated as shown in the following formula:

[0092] P s = γDS i

[0093] In the formula, γ is the heat absorption coefficient of the surface of the insulated wire, and S i is the sunlight intensity (W / m 2 ), and D is the outer diameter of the wire (m);

[0094] The calculation of the transient current-carrying capacity of the line based on the dynamic meteorological data with a remaining time of 60 min is shown in the following formula:

[0095]

[0096] In the formula, I2 is the transient current-carrying capacity of the line (A), and R ac (t) represents the AC resistance (Ω / m) at the conductor temperature t, P r represents the radiation power, P c represents the convective power of the wire, P s represents the sunlight heat absorption power of the wire (W / m), C p is the heat capacity coefficient of the wire (J / kg·°C), m is the mass per unit length of the wire (kg / m), t d is the conductor temperature (°C), T max represents the maximum operating temperature of the wire, which is selected according to the GB 50545-2010 standard, Δt is the remaining time, and ΔT s is the temperature difference between the steady-state temperature and the maximum allowable temperature of the wire.

[0097] The line safety operation constraints that need to be satisfied for setting the line safety constraint photovoltaic carrying capacity are as follows:

[0098]

[0099] In the formula: ΔP0 is the line safety constraint photovoltaic carrying capacity (kW), I2 is the transient current-carrying capacity of the line (A), and U Nis the rated line voltage (kV), I1 is the steady-state current-carrying capacity of the line (A), and ΔP t is the active power (kW) of the line's incremental photovoltaic power over 24 hours, t is the time (min), η is the line's photovoltaic output curve, and T Δ is for ΔP t > the duration (min) when P1.

[0100] Use the binary cyclic approximation method to calculate the line's photovoltaic carrying capacity that meets the line's safe operation constraint conditions.

[0101] Based on the feeder operation data, calculate the photovoltaic carrying capacity of the line's power and electricity balance, and calculate the line's photovoltaic carrying capacity under dynamically changing meteorological conditions. The calculation process is as follows:

[0102] Based on the feeder operation data, calculate the photovoltaic carrying capacity that meets the line's power and electricity balance as follows:

[0103] p g1 = min(p L,t - p pv,t )

[0104] In the formula: P g1 is the current photovoltaic carrying capacity of the line (kW), P L,t is the active power of the line's typical daily load, t is the time, and P pv,t is the active power of the photovoltaic output already connected to the line;

[0105] Calculate the photovoltaic carrying capacity of the line considering the line current-carrying capacity under dynamically changing meteorological conditions as follows:

[0106] p g = △p0 × μ + p g1

[0107] In the formula: P g is the photovoltaic carrying capacity of the line (kW), Δp0 is the line's photovoltaic carrying capacity with safety constraints calculated in step (5) (kW), μ is the percentage of the line's safety capacity, and the value of μ is selected according to the line connection form. P g1 is the photovoltaic carrying capacity (kW) that meets the line's power and electricity balance.

[0108] Example 3, as Figures 2 to 7 shown, a method for measuring the photovoltaic carrying capacity considering the dynamic current-carrying capacity of the line. Taking an actual 10kV line as an example, the specific implementation of the present invention is further described, including the following steps:

[0109] (1) Obtain and organize the dynamic meteorological data of the area where the feeder for calculating the current-carrying capacity is located and the line's basic parameters

[0110] The wire type of the 10kV feeder selected for photovoltaic load-carrying capacity calculation in the present invention is: yjv-240. The dynamic meteorological data of the area where the feeder is located in the past three years are obtained and sorted to obtain the meteorological condition data of the day with the lowest current-carrying capacity, including the solar radiation intensity, ambient temperature and wind speed within a day, as Figure 2 shown.

[0111] The line basic parameters selected in the present invention are: skin effect coefficient of the wire I = 0.0046, ratio of AC and DC resistance of the wire β = 1 + I = 1.0046, DC resistance of the conductor at 20°C R dc = 0.0000638 Ω / m, resistance temperature coefficient α 20 = 0.00356 at 20°C, radiation coefficient ε of the outer surface insulation layer of the wire = 0.38, Stefan-Boltzmann constant S = 0.0000000567, outer diameter D of the wire = 0.0171m, conductor temperature T is shown in Figure 3 , heat transfer coefficient λ of the outer insulation layer of the wire = 0.43, heat absorption coefficient γ of the surface of the insulated wire = 0.85, mass per unit length m of the wire = 2.864 kg / m, heat capacity coefficient C p = 4.36 J / kg·°C, maximum allowable temperature T max of the line = 70°C.

[0112] (2) Obtain the operating data required for the calculation of the 10kV feeder for photovoltaic load-carrying capacity calculation

[0113] Select the load on the day with the lowest current-carrying capacity described in step (1) as the typical daily load, and its load curve is as shown in the appendix Figure 5 shown. The photovoltaic output characteristic curve η of the area where the feeder is located is obtained from the annual photovoltaic output data of the feeder as shown in Figure 6 shown.

[0114] (3) Calculate the steady-state current-carrying capacity and transient current-carrying capacity with a remaining time of 60 minutes of the line based on the dynamic meteorological data and line basic parameters, and obtain the steady-state current-carrying capacity and transient current-carrying capacity with a remaining time of 60 minutes of the line as shown in Figure 4 shown.

[0115] The process of calculating the steady-state current-carrying capacity of the line and the transient current-carrying capacity with a remaining time of 60 minutes under dynamic meteorological data in the present invention is as follows:

[0116] Calculate the AC resistance R ac (t) of the wire at temperature t,

[0117]

[0118] Calculate the radiation power P r of the wire,

[0119]

[0120] Calculate the current-carrying temperature rise θ of the conductor

[0121] θ = t d - T c

[0122] Calculate the aerodynamic viscosity v of the air f

[0123] ν f = 1.32×10 -5 + 9.6(T c + θ / 2)×10 -5

[0124] Calculate the Reynolds number R e

[0125] R e = νD / ν f

[0126] Calculate the convective heat dissipation P of the wire c

[0127]

[0128] Calculate the heat P generated by the solar radiation absorption of the conductor s

[0129] P s = γDS i

[0130] Calculate the steady-state current-carrying capacity I1 of the line

[0131]

[0132] The principle of calculating the transient current-carrying capacity of the line with a remaining time of 60 min is as follows Figure 8 shown; through Figure 8 the derivation, calculate the transient current-carrying capacity I2 of the line with a remaining time of 60 min

[0133]

[0134] The selected remaining time Δt in this case is 60 min. The steady-state current-carrying capacity of the selected feeder and the transient current-carrying capacity with a remaining time of 60 min calculated by the above process are as shown in the appendix Figure 4 shown

[0135] (4) Set the safety operation constraints that need to be satisfied for the line to restrict the photovoltaic bearing capacity

[0136] According to the line safety operation conditions, the safety operation constraints that need to be satisfied for the line to restrict the photovoltaic bearing capacity set by the present invention are as follows

[0137]

[0138] (5) Calculate the line-constrained PV carrying capacity that meets the constraint conditions using the binary cyclic approximation method

[0139] The process of calculating the line-constrained PV carrying capacity that meets the line safety constraints using the binary cyclic approximation method in this invention is as follows Figure 7 shown; it can be calculated that ΔP0 = 16126.66 kW.

[0140] (6) Calculate the current PV carrying capacity of the line based on the feeder operation data, and calculate the dynamic PV carrying capacity of the line under dynamically changing meteorological conditions

[0141] The calculation process of calculating the current PV carrying capacity of the line based on the feeder operation data and calculating the dynamic PV carrying capacity of the line under dynamically changing meteorological conditions in this invention is as follows:

[0142] Calculate the PV carrying capacity that meets the line power and energy balance

[0143] p g1 = min(p L,t - p pv,t )

[0144] The PV carrying capacity P that meets the line power and energy balance calculated from the above formula g1 = 732.26 kW

[0145] Select the line safety capacity percentage μ:

[0146] Select the line safety capacity percentage μ required for this invention according to the line safety capacity percentages of different wiring methods in the design manual. The selection basis is shown in the following table:

[0147] Line connection method Percentage of line safety capacity Single radiation 80％ "2-1" single loop network 50％ "3-1" single loop network 66.7％

[0148] The feeder wiring form selected in this invention is single-radiation. From the above table, the line safety capacity percentage μ = 80%.

[0149] Calculate the PV carrying capacity of the line under dynamically changing meteorological conditions P g

[0150] p g = △p0 × μ + p g1

[0151] Calculate the line dynamic PV carrying capacity P from the above formula g = 9971.59 kW.

[0152] Calculate the PV carrying capacity of the line under fixed conditions:

[0153]

[0154] In the formula, I0 is the safety current of the selected feeder, U N is the rated voltage of the feeder, μ is the percentage of the line safety capacity, P g1 is the photovoltaic carrying capacity that satisfies the line power and electricity balance.

[0155] The fixed photovoltaic carrying capacity P of the line calculated from the line safety current g0 = 6908.21 kW, and the dynamic photovoltaic carrying capacity P of the line g Compared with it, the photovoltaic capacity is increased by 3063.38 kW, and the increase ratio is 44.34%.

[0156] Working principle: Obtain and sort out the dynamic meteorological data and line basic parameters of the area where the selected feeder for current-carrying capacity calculation is located; obtain the operation data required for the calculation of the 10 kV feeder for which the photovoltaic carrying capacity needs to be calculated; calculate the steady-state current-carrying capacity and transient current-carrying capacity with a remaining time of 60 min of the line based on the dynamic meteorological data and line basic parameters; set the line safety operation constraints that the line safety-constrained photovoltaic carrying capacity needs to meet; use the binary cyclic approximation method to calculate the line safety-constrained photovoltaic carrying capacity that meets the line safety operation constraints; calculate the photovoltaic carrying capacity that meets the line power and electricity balance based on the feeder operation data, and calculate the line photovoltaic carrying capacity under dynamically changing meteorological conditions. By calculating the line current-carrying capacity under dynamic meteorological data and calculating the line photovoltaic carrying capacity that meets the safety constraints based on the line dynamic current-carrying capacity, the photovoltaic carrying capacity that maximizes the line utilization rate is obtained, promoting the more efficient integration of distributed photovoltaics into the distribution network under the condition of meeting safe operation.

[0157] For those skilled in the art, it is obvious that the present invention is not limited to the details of the above exemplary embodiments, and without departing from the spirit or basic characteristics of the present invention, the present invention can be implemented in other specific forms. Therefore, from any point of view, the embodiments should be regarded as exemplary and non-limiting. The scope of the present invention is defined by the appended claims rather than the above description. Therefore, all changes falling within the meaning and scope of the equivalent elements of the claims are intended to be included in the present invention. Any reference signs in the claims should not be regarded as limiting the claims involved.

[0158] In addition, it should be understood that although this specification is described according to the embodiments, not every embodiment only contains an independent technical solution. This narrative way of the specification is only for clarity. Those skilled in the art should regard the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A method for calculating photovoltaic carrying capacity considering the dynamic current carrying capacity of the line, characterized by: The following steps are involved: S1. Obtain and organize the dynamic meteorological data and basic line parameters of the area where the feeder selected for current carrying capacity calculation is located; S2. Obtain the operating data required for calculating the 10kV feeder for the photovoltaic load capacity calculation; S3. Calculate the steady-state current carrying capacity of the line and the transient current carrying capacity for the remaining 60 minutes based on dynamic meteorological data and basic line parameters; S4. Set the line safety operation constraints that need to be met in calculating the line safety constraint photovoltaic carrying capacity; S5. Calculate the line safety constraint photovoltaic carrying capacity that meets the line safety operation constraint conditions using the binary cycle approximation method; S6. Calculate the photovoltaic carrying capacity that satisfies the power and electricity balance of the line based on the feeder operation data, and calculate the photovoltaic carrying capacity of the line under dynamically changing meteorological conditions.

2. The photovoltaic carrying capacity calculation method according to claim 1, characterized in that: In the S1, the dynamic meteorological data and the basic line parameters required for current carrying capacity calculation are obtained and sorted, including: the sunshine intensity, ambient temperature and wind speed in the area where the feeder is located in the past three years, and after detailed analysis and sorting of the meteorological data in the past three years, the meteorological condition data of the day that leads to the lowest current carrying capacity is selected as the basic meteorological input data for subsequent calculations; the parameters of the wires used in the feeder are obtained and sorted, including: specific model, wiring form, safety current, wire outer diameter, Still coefficient, resistance temperature coefficient, AC-DC resistance ratio, DC resistance value at 20°C, skin effect coefficient, insulation heat absorption coefficient, insulation heat transfer coefficient, insulation radiation coefficient, unit length mass, specific heat capacity and maximum allowable temperature of the wire.

3. The photovoltaic carrying capacity calculation method according to claim 1, characterized in that: In S2, the operation data required for calculating the 10kV feeder for photovoltaic load carrying capacity calculation is obtained, including: the load active power of the 10kV feeder for 20 hours on the selected day, and the photovoltaic output characteristic curve of the feeder.

4. The photovoltaic carrying capacity calculation method according to claim 1, characterized in that: In S3, the specific method for calculating the steady-state current carrying capacity of the line and the transient current carrying capacity with a remaining time of 60 minutes based on the dynamic meteorological data and the basic parameters of the line is as follows: The calculation of the steady-state current carrying capacity of the line based on dynamic meteorological data is shown in the following formula: Where I1 is the steady-state current carrying capacity of the line (A), R ac (t) represents the AC resistance of the conductor at temperature t (Ω / m), P r Represents the radiated power (W / m), P c represents the conductor convection power (W / m), P s Represents the solar heat absorption power of the conductor (W / m); Among them, the AC resistance R at the wire temperature t ac (t) The calculation method is as follows: Where I is the skin effect coefficient of the conductor, β is the AC / DC resistance ratio of the conductor; R dc is the DC resistance of the conductor at 20°C, t d is the conductor temperature (℃), α 20 is the resistance temperature coefficient when the conductor temperature is 20℃; Among them, the radiation power P r The calculation method is shown in the following formula: P r =πεSD(t d 4 -T c 4 ) Where ε is the radiation coefficient of the insulation layer on the outer surface of the conductor, S is the Stefan-Boltzmann constant; D is the outer diameter of the conductor (m), t d is the conductor temperature (°C), T c is the ambient temperature (℃); Among them, the convection heat dissipation power P c The calculation method is as follows: Where λ is the heat transfer coefficient of the conductor's external insulation layer (W·m -1 ·K -1 ), θ is the conductor current-carrying temperature rise (℃), R e is the Reynolds number; The calculation method of conductor current-carrying temperature rise θ is as follows: θ=t d -T c Reynolds number R e The calculation method is as follows: R e =νD / ν f Where, v is the wind speed (m / s), D is the outer diameter of the conductor (m), and v f is the air dynamic viscosity; Air dynamic viscosity v f The calculation method is as follows: n f =1.32×10 -5 +9.6(T c +θ / 2)×10 -5 Where, T c is the ambient temperature (℃), θ is the current-carrying temperature rise of the conductor (℃); Among them, the heat generated by the conductor's sunlight absorption is P s The calculation method is as follows: P s =γDS i Where γ is the heat absorption coefficient of the insulated wire surface, S i is the sunlight intensity (W / m 2 ), D is the outer diameter of the wire (m); The transient current carrying capacity of the line with a remaining time Δt of 60 minutes is calculated based on dynamic meteorological data as follows: Where I2 is the transient current carrying capacity of the line (A), R ac (t) represents the AC resistance of the conductor at temperature t (Ω / m), P r Represents the radiated power, P c Represents the conductor convection power, P s represents the solar heat absorption power of the conductor (W / m), C p is the conductor heat capacity coefficient (J / kg·℃), m is the conductor mass per unit length (kg / m), T is the conductor temperature (℃), t d is the conductor temperature (°C), T max represents the maximum operating temperature of the conductor (°C), selected according to GB 50545-2010 standard, Δt is the remaining time (min), ΔT s It is the temperature difference between the conductor temperature and the maximum allowable temperature (℃).

5. The photovoltaic carrying capacity calculation method according to claim 1, characterized in that: In S4, the line safety constraints that need to be met by the photovoltaic carrying capacity of the line safety constraints are set as follows: Where: ΔP0 is the line safety constraint photovoltaic carrying capacity (kW), I2 is the line transient current carrying capacity (A), U N is the line rated voltage (kV), I1 is the line steady-state current carrying capacity (A), ΔP t is the 24h active power of the incremental photovoltaic power generation of the line (kW), t is the time (min), η is the photovoltaic output curve of the line, T Δ ΔP t >Duration of P1 (min).

6. The photovoltaic carrying capacity calculation method according to claim 1, characterized in that: In S5, the binary cycle approximation method is used to calculate the line safety constraint photovoltaic carrying capacity that meets the line safety operation constraint conditions.

7. The photovoltaic carrying capacity calculation method according to claim 1, characterized in that: In S6, the photovoltaic carrying capacity of the line power balance is calculated based on the feeder operation data, and the photovoltaic carrying capacity of the line under the dynamically changing meteorological conditions is calculated. The calculation process is as follows: The PV carrying capacity that satisfies the line power balance is calculated based on the feeder operation data as follows: on g1 =min(p L,t -p pv,t ) Where: P g1 is the current photovoltaic carrying capacity of the line (kW), P L,t is the typical daily load active power of the line, t is the time, P pv,t The active power of the photovoltaic power output connected to the line; The photovoltaic carrying capacity of the line considering the line current carrying capacity under dynamically changing meteorological conditions is calculated as follows: p g =△p0×μ+p g1 Where: P g is the line PV carrying capacity (kW), Δp0 is the line safety constraint PV carrying capacity (kW) calculated in step (5), μ is the line safety capacity percentage, and the μ value is selected according to the line wiring form, P g1 The photovoltaic carrying capacity (kW) required to meet the power balance of the line.

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