An optimization calculation method for the comprehensive efficiency of energy storage power stations

Abstract

The present invention provides a method for optimizing the comprehensive efficiency of an energy storage power station, belonging to the technical field of operation evaluation and data calculation of energy storage power stations. The method solves the problem that traditional calculation methods do not consider transient loss processes. The method comprises respectively calculating loss optimization coefficients corresponding to the efficiency of the step-up transformer, the efficiency of the main transformer, and the efficiency of the cable line. Based on the calculation results of the loss optimization coefficients, while ignoring no-load losses in the calculation of the efficiency of the step-up transformer and the efficiency of the main transformer, an optimization calculation formula for the comprehensive efficiency η is derived. The loss optimization coefficient is used to quantitatively reflect the process in which the resistance and loss of the conductors of the step-up transformer, the main transformer, and the cable line gradually increase during the transient process of heating from ambient temperature to steady-state temperature. The comprehensive efficiency of the energy storage power station calculated using this method is more accurate due to the consideration of transient processes, and the comprehensive efficiency is improved, which is an important basis for economic evaluation and investment decision-making.

Description

Technical Field

[0001] The present invention belongs to the technical field of operation evaluation and data calculation of energy storage power stations, and particularly relates to a method for optimizing calculation of the comprehensive efficiency of energy storage power stations. Background Art

[0002] Comprehensive efficiency is a key technical indicator for large-scale energy storage power stations. Its calculation is based on the efficiency of each subsystem and component equipment within the power storage station. The comprehensive efficiency of an energy storage station is defined as the ratio of online power to offline power during the station's production and operation period. Therefore, comprehensive efficiency is a comprehensive assessment indicator that takes into account indicators such as the energy storage loss rate, station power consumption rate, transformer and distribution loss rate, and the energy efficiency of the storage unit charge and discharge.

[0003] Comprehensive efficiency should be measured at the grid connection point, using the following formula: Comprehensive efficiency = discharged power / (charged capacity + all auxiliary control power supplies) * 100. Auxiliary control power supplies may include equipment such as battery cooling systems and monitoring systems. Comprehensive efficiency reflects the operation and maintenance costs and economic performance of the energy storage plant. It serves as a comprehensive evaluation standard for the performance and integration level of all equipment in the energy storage plant and system. It is also a key basis for economic evaluation and investment decision-making during energy storage project construction. The comprehensive efficiency of energy storage plants must undergo rigorous technical theoretical calculations to avoid significant deviations from the promised values at project commissioning, which could result in significant fines.

[0004] The traditional calculation formula for the comprehensive efficiency of lithium iron phosphate energy storage power stations is as follows:

[0005]

[0006] In the above formula, η i Including battery system efficiency, PCS efficiency, step-up transformer efficiency, main transformer efficiency and cable line charging and discharging efficiency; the efficiency of each device calculated separately is multiplied to obtain the comprehensive efficiency result, n represents the total number of devices, for example, if a calculation only includes the efficiency calculation of the above five parts, then n = 5; R S It is the self-use electricity efficiency of the energy storage power station (including battery cooling system and monitoring system, etc.).

[0007] When applying the above-mentioned traditional calculation formula to calculate comprehensive efficiency, the battery system efficiency and PCS efficiency are guaranteed and provided by the manufacturer, and the energy storage station's self-consumption rate is calculated and determined by load. However, the traditional calculation of the step-up transformer efficiency, main transformer efficiency, and cable line charge and discharge efficiency only considers the case of steady-state continuous load at rated capacity. As shown in the actual process described below, due to the influence of the insulation thermal resistance and heat capacity of the conductors of each transformer and cable, the conductor undergoes a transient process from ambient temperature to steady-state temperature, during which the conductor resistance and losses also gradually increase. The duration of this transient process is generally measured in hours. Since lithium iron phosphate energy storage stations are energy-type energy storage stations, the charge and discharge time is typically 2 hours. Therefore, the duration of the transient process cannot be ignored relative to the charge and discharge duration. This is a shortcoming of the traditional energy storage station comprehensive efficiency calculation method, resulting in errors in the calculated results compared to the actual situation. Since the comprehensive efficiency calculation results of energy storage stations have a significant impact on economic benefit analysis, the traditional calculation method may lead to significant errors in the assessment of production benefits, affecting subsequent production and development processes. Summary of the Invention

[0008] To more accurately calculate the overall efficiency of an energy storage power station and avoid the shortcomings of prior art, the present invention fully considers the influence of conductor insulation thermal resistance and heat capacity. It also incorporates the transient characteristics of the step-up transformer efficiency, cable line efficiency, and main transformer efficiency when calculating the overall efficiency of the energy storage power station. This results in a method for optimizing the overall efficiency of an energy storage power station, achieving more accurate and practical calculation results.

[0009] The present invention adopts the following technical solutions to achieve the purpose:

[0010] A method for optimizing the overall efficiency of an energy storage power station is proposed. The loss optimization coefficients corresponding to the step-up transformer efficiency, the main transformer efficiency, and the cable line efficiency are calculated respectively. Based on the calculation results of the loss optimization coefficients, while ignoring the no-load loss in the calculation of the step-up transformer efficiency and the main transformer efficiency, the optimization calculation formula for the overall efficiency η is obtained as follows:

[0011]

[0012] In the above formula, η i is the battery system efficiency and PCS efficiency; R S is the self-use efficiency of the energy storage power station; the ordinal number m is the total number of battery systems and PCS equipment; η j k is the efficiency of the step-up transformer, main transformer and cable line at rated conditions; j are the loss optimization coefficients corresponding to the step-up transformer, main transformer and cable line respectively; the ordinal number n is the total number of equipment including the step-up transformer, main transformer and cable line; i and j are the serial numbers of the multiplication.

[0013] Specifically, the loss optimization coefficient is used to quantitatively reflect the process in which the resistance and loss of the conductors of the step-up transformer, main transformer and cable line gradually increase during the transient process of heating from ambient temperature to steady-state temperature.

[0014] Furthermore, in the calculation of the loss optimization coefficient of the boost transformer efficiency, the boost transformer is a dry-type boost transformer, and the calculation of the loss optimization coefficient specifically includes: calculating the load loss at the rated capacity of the transformer, in kW; calculating the total resistance of the primary and secondary windings of the transformer at different temperatures, in Ω; calculating the average temperature rise of the transformer winding, in K; based on the above calculation results, deriving the load loss formula required for the actual calculation of the boost transformer efficiency, and thus deriving the loss optimization coefficient of the boost transformer efficiency based on the calculation results of the formula.

[0015] Furthermore, the load loss P when calculating the rated capacity of the transformer is kN , the formula is:

[0016]

[0017] In the above formula, I 1N is the rated phase current of the primary winding, I 2N is the rated phase current of the secondary winding, both in A; R 1N is the total resistance of the primary winding under rated operating conditions, R 2N is the total resistance of the secondary winding under rated operating conditions, and the unit is Ω.

[0018] Furthermore, the total resistance R of the primary and secondary windings of the transformer at different temperatures is calculated, that is, R 1N and R 2N The calculation methods are as follows:

[0019] R=R0[1+3.93×10 -3 (θ-20)]

[0020] In the above formula, R0 is the resistance value when the resistor temperature is 20℃; θ is the actual temperature of the resistor; 1N and R 2N After substituting the corresponding R0 values, the total resistance R of the primary and secondary windings of the transformer can be obtained.

[0021] Furthermore, the calculation of the average temperature rise of the transformer winding includes:

[0022] Calculate the winding hot spot temperature rise Δθ under continuous load HSn , the formula is:

[0023]

[0024] In the above formula, Δθ Wr is the average temperature rise of the winding of the dry-type step-up transformer under rated load, in K; I n For a given load rate;

[0025] Calculate the winding hot spot temperature rise Δθ during transient load t , the formula is:

[0026]

[0027] In the above formula, Δθ t is the temperature rise after the load changes for t time; Δθ i For a certain load rate I n Initial temperature rise at the beginning; Δθ U is the load factor I n The final temperature rise without change, that is, the temperature rise Δθ under continuous load HSn , the unit of temperature rise is K; τ is the time constant of the winding under a given load; t is time, and the unit of time constant and time is min.

[0028] Furthermore, based on the load loss P calculated when the transformer is rated capacity kN , the total resistance R of the primary and secondary windings of the transformer at different temperatures, combined with the calculation of the winding hot spot temperature rise during transient load, take Δθ U The value is 80K, take Δθ i The value is 20K, the τ value is 90min, and the actual charge and discharge time is 120min, and the load loss P required for the actual calculation of the step-up transformer efficiency is obtained. K1 , the formula is:

[0029]

[0030] According to the calculation results of the formula, the loss optimization coefficient value k1 of the step-up transformer efficiency is 0.868.

[0031] Furthermore, the load loss P at rated capacity is calculated in combination with the actual load loss of the step-up transformer. kN and the total resistance R of the primary and secondary windings of the transformer at different temperatures. The loss optimization coefficient of the main transformer efficiency is calculated specifically as follows: the main transformer includes an oil-immersed transformer, and the winding hot spot temperature rise of the main transformer winding during transient load is calculated using the formula:

[0032]

[0033] In the above formula, θ W0 is the steady-state temperature difference between the winding and the oil; θ0 is the steady-state temperature rise of the oil, and the unit of temperature rise is K; τ wis the thermal time constant of the winding, τ0 is the thermal time constant of the oil, and the unit of thermal time constant is min.

[0034] Furthermore, in combination with the calculation of the winding hot spot temperature rise of the main transformer winding during transient load, take θ W0 The value is 25K, the θ0 value is 40K, the average temperature rise of the main transformer winding is 65K, and the τ w The load loss P required for the actual calculation of the main transformer efficiency is obtained. K2 , the formula is:

[0035]

[0036] According to the calculation results of the formula, the loss optimization coefficient value k2 of the main transformer efficiency is 0.928.

[0037] Furthermore, the load loss P at rated capacity is calculated in combination with the actual load loss of the step-up transformer. kN and the total resistance R of the primary and secondary windings of the transformer at different temperatures. The loss optimization coefficient of the cable line efficiency is calculated specifically by calculating the transient temperature rise of the cable line. The formula is:

[0038]

[0039] Q C =I 2 R C

[0040] In the above formula, Q C is the total loss of three-phase conductors per unit length of cable, in W / m; R C is the resistance per unit length of the cable conductor, in Ω / m; τ is the thermal time constant of the cable system, in min; θ0 is the ambient temperature; R is the thermal resistance of the cable system including the external soil or air;

[0041] Take the value of θ0 as 20K, the maximum temperature rise of the cable is 70℃, and the value of τ is 240min. Combined with the calculation process of the actual load loss of the step-up transformer, the load loss P at rated capacity is kN The total resistance R of the primary and secondary windings of the transformer at different temperatures is used to obtain the load loss P required for the actual calculation of the cable line efficiency. K3 , the formula is:

[0042]

[0043] According to the calculation results of the formula, the loss optimization coefficient value k3 of the cable line efficiency is 0.83.

[0044] In summary, due to the adoption of this technical solution, the beneficial effects of the present invention are as follows:

[0045] Taking into full account the influence of conductor insulation thermal resistance and heat capacity during the actual operation of energy storage power stations, the conductors of energy storage station transformers, cables, etc., which experience a transient process of heating from ambient temperature to a steady-state temperature. The calculation method of the present invention takes into account the influence of transient characteristics of the step-up transformer, cable lines, and main transformer on the result when calculating the comprehensive efficiency of the energy storage power station, thus making the calculation results more accurate. Traditional calculation results that do not consider these influences are often too low. Combined with actual calculation data, the calculation method of the present invention significantly improves the comprehensive efficiency calculation results of energy storage power stations, thereby providing a more accurate reference value for economic evaluation and investment decision-making of energy storage project construction. DETAILED DESCRIPTION

[0046] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions in the embodiments of the present invention will be described clearly and completely below. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Generally, the components of the embodiments of the present invention described and illustrated herein can be arranged and designed in various different configurations.

[0047] Therefore, the following detailed description of the embodiments of the present invention is not intended to limit the scope of the claimed invention, but rather merely represents selected embodiments of the present invention. All other embodiments derived by persons of ordinary skill in the art based on the embodiments of the present invention without creative effort are intended to fall within the scope of protection of the present invention.

[0048] Example 1

[0049] A method for optimizing the overall efficiency of an energy storage power station is proposed. The loss optimization coefficients corresponding to the step-up transformer efficiency, the main transformer efficiency, and the cable line efficiency are calculated respectively. Based on the calculation results of the loss optimization coefficients, while ignoring the no-load loss in the calculation of the step-up transformer efficiency and the main transformer efficiency, the optimization calculation formula for the overall efficiency η is obtained as follows:

[0050]

[0051] In the above formula, η i is the battery system efficiency and PCS efficiency; R S is the self-use efficiency of the energy storage power station; the ordinal number m is the total number of battery systems and PCS equipment; η j k is the efficiency of the step-up transformer, main transformer and cable line at rated conditions; jare the loss optimization coefficients corresponding to the step-up transformer, main transformer and cable line respectively; the ordinal number n is the total number of equipment including the step-up transformer, main transformer and cable line; i and j are the serial numbers of the multiplication.

[0052] In this embodiment, the energy storage power station is a lithium iron phosphate energy storage power station. As an energy-type energy storage power station, the current charging and discharging time is generally 2 hours. The efficiency of the battery system and PCS is guaranteed and provided by the manufacturer, and the self-use rate is determined by load calculation. Due to the influence of the insulation thermal resistance and heat capacity of the conductor, the conductors of transformers and cables undergo a transient process of heating from ambient temperature to steady-state temperature. At this time, the resistance and loss of the conductor also gradually increase. The duration of this transient process is generally measured in hours, and the relative charging and discharging duration cannot be ignored. Therefore, the loss and efficiency of the step-up transformer, main transformer, and cable line can be optimized and calculated in combination with the transient temperature rise; the introduced loss optimization coefficient is used to quantitatively reflect the process in which the resistance and loss of the conductor gradually increase during the transient process of the step-up transformer, main transformer, and cable line heating from ambient temperature to steady-state temperature.

[0053] In calculating the loss optimization coefficient of the step-up transformer efficiency, the step-up transformer is a dry-type step-up transformer. The calculation of the loss optimization coefficient specifically includes: calculating the load loss at the rated capacity of the transformer, in kW; calculating the total resistance of the primary and secondary windings of the transformer at different temperatures, in Ω; calculating the average temperature rise of the transformer winding, in K; based on the above calculation results, the load loss formula required for the actual calculation of the step-up transformer efficiency is obtained, and then the loss optimization coefficient of the step-up transformer efficiency is obtained based on the calculation results of the formula.

[0054] The formula for calculating the rated efficiency of the transformer is:

[0055]

[0056] Where: S N is the rated capacity of the transformer (kVA); is the transformer secondary side power factor; P0 is the transformer no-load loss (kW); P KN is the load loss (kW) at rated capacity of the transformer.

[0057] The no-load loss of a transformer includes hysteresis loss, eddy current loss, and additional loss of the core material, and generally does not change with the load factor. Therefore, in the optimization calculation method of this embodiment, since the calculation of the transient process is fully considered, the no-load loss calculation can be ignored, which reduces the calculation burden. The load loss is the main calculation object, mainly referring to the basic copper loss. The additional loss caused by the leakage magnetic field is very small.

[0058] Calculate the load loss P at rated capacity of the transformer kN , the formula is:

[0059]

[0060] In the above formula, I 1N is the rated phase current of the primary winding, I 2N is the rated phase current of the secondary winding, both in A; R 1N is the total resistance of the primary winding under rated operating conditions, R 2N is the total resistance of the secondary winding under rated operating conditions, and the unit is Ω.

[0061] Calculate the total resistance R of the primary and secondary windings of the transformer at different temperatures, that is, R 1N and R 2N The calculation methods are as follows:

[0062] R=R0[1+3.93×10 -3 (θ-20)]

[0063] In the above formula, R0 is the resistance value when the resistor temperature is 20℃; θ is the actual temperature of the resistor; 1N and R 2N After substituting the corresponding R0 values, the total resistance R of the primary and secondary windings of the transformer can be obtained.

[0064] According to GB / T1094.12, the formula for calculating the average temperature rise of the winding of a Class B temperature rise transformer is as follows, including:

[0065] Calculate the winding hot spot temperature rise Δθ under continuous load HSn , the formula is:

[0066]

[0067] In the above formula, Δθ Wr is the average temperature rise of the winding of the dry-type step-up transformer under rated load, in K; I n For a given load rate;

[0068] Calculate the winding hot spot temperature rise Δθ during transient load t , the formula is:

[0069]

[0070] In the above formula, Δθ t is the temperature rise after the load changes for t time; Δθ i For a certain load rate I n Initial temperature rise at the beginning; Δθ U is the load factor I n The final temperature rise without change, that is, the temperature rise Δθ under continuous load HSn, the unit of temperature rise is K; τ is the time constant of the winding under a given load; t is time, and the unit of time constant and time is min.

[0071] The physical meaning of the thermal time constant τ is the time it takes for the transformer temperature rise to reach 63.2% of the total temperature rise from zero. Correction should be made for naturally air-cooled dry transformers with different loads and starting temperatures, but no correction is required in this case. Time constant τ at rated load R It can be obtained by calculation or test. For transformers with a capacity of 800kVA to 1600kVA, the calculation result tends to be conservative when it is taken as 90 minutes.

[0072] From the above analysis, it can be seen that the load loss P when the rated capacity of the transformer is calculated based on the above kN , the total resistance R of the primary and secondary windings of the transformer at different temperatures, combined with the winding hot spot temperature rise during the calculation of transient load, take Δθ U The value is 80K, take Δθ i The value is 20K, the τ value is 90min, and the actual charge and discharge time is 120min, and the load loss P required for the actual calculation of the step-up transformer efficiency is obtained. K1 , the formula is:

[0073]

[0074]

[0075] According to the calculation results of the formula, the loss optimization coefficient value k1 of the step-up transformer efficiency is 0.868.

[0076] where Δθ i For conservative calculation, the maximum annual average temperature in GB / T1094.11 can be taken as 20°C.

[0077] Combined with the calculation process of the actual load loss of the step-up transformer, the load loss P at rated capacity kN and the total resistance R of the primary and secondary windings of the transformer at different temperatures. The loss optimization coefficient of the main transformer efficiency is calculated specifically as follows: the main transformer includes an oil-immersed transformer. The oil-immersed transformer has two thermal time constants, the thermal time constant of the winding and the thermal time constant of the oil, which respectively reflect the temperature rise characteristics of the winding insulation paper and the transformer oil.

[0078] The formula for calculating the hot spot temperature rise of the main transformer winding during transient load is:

[0079]

[0080] In the above formula, θ W0 is the steady-state temperature difference between the winding and the oil; θ0 is the steady-state temperature rise of the oil, and the unit of temperature rise is K; τw is the thermal time constant of the winding, τ0 is the thermal time constant of the oil, and the unit of thermal time constant is min.

[0081] Combined with the calculation of the winding hot spot temperature rise of the main transformer winding during transient load, take θ W0 The value is 25K, the θ0 value is 40K, the average temperature rise of the main transformer winding is 65K according to GB / T1094.7, and the τ w The load loss P required for the actual calculation of the main transformer efficiency is obtained. K2 , the formula is:

[0082]

[0083] According to the calculation results of the formula, the loss optimization coefficient value k2 of the main transformer efficiency is 0.928.

[0084] Then calculate the transient temperature rise of the cable line, and combine the load loss P at rated capacity with the actual load loss calculation of the step-up transformer. kN The total resistance R of the primary and secondary windings of the transformer at different temperatures is used to calculate the loss optimization coefficient of the cable line efficiency. Specifically, the transient temperature rise of the cable line is calculated. According to the thermal balance principle, when a constant load of current I passes through the cable, the following transient temperature rise formula can be obtained by solving the differential equation:

[0085]

[0086] Q C =I 2 R C

[0087] In the above formula, Q C is the total loss of three-phase conductors per unit length of cable, in W / m; R C is the resistance per unit length of the cable conductor, in Ω / m; τ is the thermal time constant of the cable system, in min; θ0 is the ambient temperature; R is the thermal resistance of the cable system including the external soil or air;

[0088] Also consider that the charge and discharge time is 2 hours. In the transient process, the θ0 value is taken as 20K. At this time, the maximum temperature rise of the cable is 70℃, and the thermal time constant τ of the cable system is taken as 240min. Combined with the calculation process of the actual load loss of the step-up transformer, the load loss P at rated capacity is calculated. kN The total resistance R of the primary and secondary windings of the transformer at different temperatures is used to obtain the load loss P required for the actual calculation of the cable line efficiency. K3 , the formula is:

[0089]

[0090] According to the calculation results of the formula, the loss optimization coefficient value k3 of the cable line efficiency is 0.83.

[0091] After completing the above calculations and obtaining the values of k1, k2, and k3, which correspond to the loss optimization coefficients of the step-up transformer, main transformer, and cable line respectively, substituting them into the optimization calculation formula of the comprehensive efficiency η, the comprehensive efficiency result after optimization calculation can be finally obtained.

[0092] Example 2

[0093] Based on Example 1, the calculation result data examples of this embodiment using the method of Example 1 are as follows:

[0094] Calculate the comprehensive efficiency of a 103MW / 206MWh lithium iron phosphate energy storage power station.

[0095] When the step-up transformer uses a natural air-cooled dry-type transformer of different capacities, the comprehensive efficiency calculation results before optimization are as follows:

[0096] Table 1 Calculation table of comprehensive efficiency of energy storage power station before optimization

[0097] Serial number Device Name Charging efficiency Discharge efficiency Comprehensive efficiency 1 Battery system 97.00％ 97.00％ 94.09％ 2 PCS 98.40％ 98.40％ 96.83％ 3 step-up transformer 99.00％ 99.00％ 98.01％ 4 Line loss 99.00％ 99.00％ 98.01％ 5 Auxiliary power loss 98.55％ 98.55％ 97.12％ 6 Main transformer 99.65％ 99.65％ 99.30％ 7 Total efficiency 91.87％ 91.87％ 84.40％

[0098] The transformer and line efficiencies in Table 1 are for continuous operation. The overall efficiency, corrected for transient temperature rise, is calculated as shown in Table 2. For example, the optimized efficiency of the step-up transformer is calculated as: 1 - (1 - 99%) * 0.868 = 99.13%.

[0099] Table 2 Calculation table of comprehensive efficiency of energy storage power station after optimization

[0100] Serial number Device Name Charging efficiency Discharge efficiency Comprehensive efficiency 1 Battery system 97.00％ 97.00％ 94.09％ 2 PCS 98.40％ 98.40％ 96.83％ 3 step-up transformer 99.13％ 99.13％ 98.27％ 4 Line loss 99.13％ 99.13％ 98.27％ 5 Auxiliary power loss 98.55％ 98.55％ 97.12％ 6 Main transformer 99.68％ 99.68％ 99.35％ 7 Total efficiency 92.14％ 92.14％ 84.89％

[0101] The calculation results of the energy storage power station show that the calculation method of the present invention increases the overall efficiency of the energy storage power station by 0.49%. Even with this numerical increase, as a comprehensive efficiency, it can play a positive role in the benefit analysis and development of large-scale energy storage power stations. In terms of the calculation accuracy of the comprehensive efficiency of the energy storage power station, the improvement effect is more obvious.

Claims

1. A method for optimizing the overall efficiency of an energy storage power station, characterized by: Calculate the loss optimization coefficients corresponding to the step-up transformer efficiency, main transformer efficiency and cable line efficiency respectively. Based on the calculation results of the loss optimization coefficients, while ignoring the no-load loss in the calculation process of the step-up transformer efficiency and main transformer efficiency, the comprehensive efficiency is obtained. The optimization calculation formula is: In the above formula, is the battery system efficiency and PCS efficiency; The efficiency of energy storage power station’s self-use electricity; The total number of devices for the battery system and PCS; The efficiency of the step-up transformer, main transformer and cable line at rated conditions; are the loss optimization coefficients corresponding to the step-up transformer, main transformer and cable line respectively; The total number of equipment for step-up transformers, main transformers and cable lines; 、 is the number of consecutive multiplications; Calculate the loss optimization factor for step-up transformer efficiency, including: Calculate the load loss at rated transformer capacity , unit is kW; calculate the total resistance of the primary and secondary windings of the transformer at different temperatures , unit is Q; calculate the average temperature rise of the transformer winding, unit is K; according to the above calculation results, the load loss formula required for the actual calculation of the step-up transformer efficiency is obtained, and then the loss optimization coefficient value of the step-up transformer efficiency is obtained according to the calculation results of the formula ; Calculate the loss optimization factor of the main transformer efficiency, including: Calculate the winding hot spot temperature rise during transient load of the main transformer winding , combined with the load loss at the rated capacity of the transformer The total resistance of the primary and secondary windings of the transformer at different temperatures , the load loss formula required for the actual calculation of the main transformer efficiency is obtained, and the loss optimization coefficient value of the main transformer efficiency is obtained based on the calculation results of the formula ; Calculate the loss optimization factor of the cable line efficiency, including: the total loss of the three-phase conductor per unit length of cable , calculate the transient temperature rise of the cable line , combined with the load loss at the rated capacity of the transformer The total resistance of the primary and secondary windings of the transformer at different temperatures , and obtain the load loss formula required for the actual calculation of cable line efficiency, and then obtain the loss optimization coefficient value of cable line efficiency based on the calculation results of the formula .

2. The method for optimizing the overall efficiency of an energy storage power station according to claim 1, characterized in that: The loss optimization coefficient is used to quantitatively reflect the process in which the resistance and loss of the conductors of the step-up transformer, main transformer and cable line gradually increase during the transient process of heating from ambient temperature to steady-state temperature.

3. The method for optimizing the overall efficiency of an energy storage power station according to claim 1, wherein: The step-up transformer is a dry-type step-up transformer.

4. The method for optimizing the comprehensive efficiency of an energy storage power station according to claim 3, characterized in that: The load loss when calculating the rated capacity of the transformer , the formula is: In the above formula, is the rated phase current of the primary winding, is the rated phase current of the secondary winding, both in A; is the total resistance of the primary winding under rated operating conditions, is the total resistance of the secondary winding under rated operating conditions, and the units are .

5. The method for optimizing the comprehensive efficiency of an energy storage power station according to claim 4, characterized in that: The total resistance of the primary and secondary windings of the transformer at different temperatures is calculated ,Right now and The calculation methods are as follows: In the above formula, The resistance temperature is The resistance value when is the actual temperature of the resistor; and Corresponding to After substituting the value, the total resistance of the primary and secondary windings of the transformer can be obtained. .

6. The method for optimizing the overall efficiency of an energy storage power station according to claim 5, characterized in that: The calculation of the average temperature rise of the transformer winding includes: Calculation of the winding hot spot temperature rise under continuous load , the formula is: In the above formula, is the average temperature rise of the winding of the dry-type step-up transformer under rated load, in K; For a given load rate; Calculation of winding hot spot temperature rise during transient load , the formula is: In the above formula, For load changes Temperature rise after time; For a certain load rate Initial temperature rise at the beginning; is the load factor The final temperature rise without change, that is, the temperature rise under continuous load , the unit of temperature rise is K; is the time constant of the winding under a given load; is time, and the unit of time constant and time is min.

7. The method for optimizing the comprehensive efficiency of an energy storage power station according to claim 6, characterized in that: Based on the above calculation of the load loss when the transformer is rated capacity , the total resistance of the primary and secondary windings of the transformer at different temperatures , combined with the calculation of the winding hot spot temperature rise during transient load, take The value is 80K, The value is 20K, take The value is 90min, and the actual charge and discharge time is 120min, and the load loss required for the actual calculation of the step-up transformer efficiency is obtained. , the formula is: The loss optimization coefficient value of the step-up transformer efficiency is obtained based on the calculation results of the formula It is 0.

868.

8. The method for optimizing the overall efficiency of an energy storage power station according to claim 5, characterized in that: The main transformer includes an oil-immersed transformer. The main transformer winding hot spot temperature rise during transient load The calculation formula is: In the above formula, is the steady-state error of the winding to the oil; is the steady-state temperature rise of the oil, and the unit of temperature rise is K; is the thermal time constant of the winding, is the thermal time constant of the oil, and the unit of thermal time constant is min.

9. The method for optimizing the comprehensive efficiency of an energy storage power station according to claim 8, characterized in that: Combined with the winding hot spot temperature rise of the main transformer winding during transient load, the The value is 25K, take The value is 40K, the average temperature rise of the main transformer winding is 65K, The value is 5min, take The value is 90min, which gives the load loss required for the actual calculation of the main transformer efficiency. , the formula is: The loss optimization coefficient value of the main transformer efficiency is obtained based on the calculation results of the formula It is 0.

928.

10. The method for optimizing and calculating the comprehensive efficiency of an energy storage power station according to claim 5, characterized in that: Transient temperature rise of cable lines The calculation formula is: In the above formula, is the total loss of three-phase conductors per unit length of cable, in W / m; is the resistance per unit length of the cable conductor, in units of / m; is the thermal time constant of the cable system, in min; is the ambient temperature; The thermal resistance of the cable system including the external soil or air; Pick The value is 20K, at this time the highest temperature rise of the cable is 70℃, The value is 240min, combined with the load loss at rated capacity during the calculation of the actual load loss of the step-up transformer The total resistance of the primary and secondary windings of the transformer at different temperatures , the load loss required for actual calculation of cable line efficiency is obtained , the formula is: The loss optimization coefficient value of the cable line efficiency is obtained based on the calculation results of the formula It is 0.83.

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