A control method for optimizing the operation of a distribution transformer

Abstract

The application discloses a control method for optimizing operation of distribution transformers, and belongs to the field of distribution transformers, aiming to provide an optimal solution to the problem of power loss of distribution transformers under the condition of considering the change of load operation and other factors. The power loss of the transformer is finally determined by considering the influence of the actual operation voltage and the service life of the power transformer on the power loss of the transformer, and considering two factors of the time of the transformer accessing the distribution network and the power load plan, so as to improve the operation efficiency of the distribution transformer, thereby improving the overall operation efficiency of the power system. For the distribution room with seasonal load change, the power loss and energy loss of the distribution transformer can be significantly reduced, so that the improvement of the operation efficiency of the distribution network transformer has important significance.

Description

Technical Field

[0001] This invention relates to the field of power distribution transformer devices or systems, and more specifically, to a control method for a power distribution transformer. Background Technology

[0002] The key equipment generating power losses in a power system includes generators, transmission lines, and transformers. Therefore, maximizing the overall benefits of the power system is achieved when these devices operate at maximum efficiency and minimum operating costs. In recent years, with the rapid development of my country's economy, electricity consumption by factories, enterprises, and shopping malls has increased daily, making the efficient operation of the power grid increasingly important. Transformers account for a high proportion of losses in the power system, and their operating efficiency directly affects the efficiency of the power system. Transformers are considered static equipment, with a design life typically of 20 years or longer. Transformers mainly include power transformers, distribution transformers, and small transformers. Except for small transformers, the efficiency of power transformers and distribution transformers is typically between 95% and 98.5%, and the efficiency of large transformers is even higher. Furthermore, a power system contains a large number of transformers, making transformer operating efficiency a crucial factor to consider for the overall system efficiency.

[0003] For example, Chinese patent document CN113258682B discloses an intelligent control method and system for optimizing transformer operation. This method obtains parameter information affecting the characteristic information of a first transformer, optimizes the first transformer based on the first optimization result, and obtains a second transformer, thus addressing the problem of low intelligence in the optimization of transformer operation. However, because this technical solution does not consider the power loss of the transformer caused by factors such as changes in load operation, it is not suitable for application in the operation optimization of distribution transformers. Summary of the Invention

[0004] The technical problem this invention aims to solve is to optimize the power loss of distribution transformers under varying load conditions, thereby improving their operating efficiency. This invention provides a method for optimizing transformer operation by considering the impact of actual operating voltage and transformer lifespan on power loss, and taking into account the transformer's connection time to the distribution network and power load planning to ultimately determine optimal transformer operation, thus improving the overall operating efficiency of the power system.

[0005] The technical solution adopted in this invention is: a control method for optimizing the operation of distribution transformers, the method comprising the following steps:

[0006] S1: Determine whether the load rate of the currently operating distribution transformer is lower than the optimal load rate value; the load rate is the ratio of the transformer's actual capacity to its rated capacity.

[0007] S2: If so, establish a power loss model for the distribution transformer, aiming to minimize the power loss of the distribution transformer, and obtain the minimum load rate; adjust the operating state of the distribution transformer to make the load rate close to the optimal load rate.

[0008] S3: Measure the actual value of no-load loss, measure the inferred value of no-load loss, and measure the short-circuit loss value.

[0009] S4: Considering the actual operating voltage, the service life of the distribution transformer, the time when the distribution transformer is connected to the distribution network, and the power load plan, establish an energy loss model for the distribution transformer to obtain the optimal load value and the best long-term load rate.

[0010] S5: Adjust the operating status of the distribution transformer according to the optimal long-term load rate.

[0011] This method aims to minimize transformer power loss, taking into account the impact of actual operating voltage and the lifespan of the power transformer on its power loss, and also considering the timing of transformer connection to the distribution network and power load planning to ultimately determine the economical operating mode of the transformer.

[0012] Furthermore, the optimal load of the distribution transformer described in step S1 is expressed by the formula:

[0013]

[0014] Among them, S B S represents the rated capacity of the transformer. OPT The optimal capacity for economical operation of the transformer; ΔP NL For the no-load loss of the transformer; ΔP SL This refers to the short-circuit loss of the transformer;

[0015] The optimal load factor k of the distribution transformer L The ratio of the optimal load to the rated capacity of a distribution transformer is expressed by the following formula:

[0016]

[0017] When using the above formula, since the ratio of no-load loss to short-circuit loss of a distribution transformer varies between 3.3 and 5.0, the load rate of a distribution transformer is generally low, varying between 0.45 and 0.55. The load rate of currently operating distribution transformers is generally lower than the optimal load rate, and most of their operating conditions are under non-optimal operating modes.

[0018] Furthermore, the power loss model of the distribution transformer described in step S2 is as follows:

[0019]

[0020] Where U is the actual voltage at the high-voltage side port of the transformer, in kV; U B It is the rated voltage of the high-voltage side port of the transformer.

[0021] Furthermore, the energy loss model of the distribution transformer described in step S4 is determined by the shape coefficients of the distribution transformer's operating time and load plan, as follows:

[0022]

[0023] Among them, T Y τ is the annual operating time of the transformer, in hours; τ is the operating time of the transformer at maximum power loss, which is determined by the actual planned load value or the number of hours of maximum load, in hours.

[0024] Furthermore, the maximum power loss operating time of the transformer is:

[0025] τ=LSF·T

[0026]

[0027] Where LSF is the load loss factor, with coefficient k taking a value of 0.33 and T taking a value of 8760 hours.

[0028] Furthermore, the optimal load value is:

[0029]

[0030] Among them, S B S represents the rated capacity of the transformer. OPT The optimal capacity for economical operation of the transformer; ΔP NL For the no-load loss of the transformer; ΔP SL For the short-circuit loss of the transformer, T Y τ is the annual operating time of the transformer; τ is the operating time of the transformer at maximum power loss.

[0031] Furthermore, the no-load loss inference value only considers distribution transformers with a service life exceeding 20 years. When calculating their no-load loss, it should be increased by 1.75% for each year of operation exceeding 20 years. The model is as follows:

[0032] ΔP NL,LT =ΔP NL [1+0.0175(T LT -20)]

[0033] Among them, T LT This represents the service life of the transformer, expressed in years.

[0034] Furthermore, the optimal long-term load factor described in step S4 is:

[0035]

[0036] U is the actual voltage at the high-voltage side port of the transformer, in kV; U B It is the rated voltage at the high-voltage side port of the transformer; ΔP NL,LT This is the inferred value of no-load loss; ΔP SL τ is the short-circuit loss of the transformer; τ is the time during which the transformer operates at maximum power loss.

[0037] Further, step S5 specifically involves: adjusting the operating status of the distribution transformers according to the optimal long-term load rate through an intelligent switching control device, wherein the intelligent switching device controls multiple distribution transformers to start or stop operation.

[0038] In summary, compared with the prior art, this invention optimizes the power loss of distribution transformers by considering the impact of actual operating voltage and the service life of the power transformer on the transformer's power loss, and by taking into account the changes in the transformer's connection time to the distribution network and the power load plan, thereby improving the operating efficiency of distribution transformers. Attached Figure Description

[0039] Figure 1 This is a flowchart of the control method for optimizing the operation of distribution transformers according to the present invention;

[0040] Figure 2 The graph shows the relationship between minimum power loss, energy loss, and transformer power.

[0041] Figure 3 The diagram shows the total load of the power distribution room and the operation of the power distribution transformers before optimization.

[0042] Figure 4 The diagram shows the total load of the power distribution room and the optimized operation of the power distribution transformer.

[0043] Figure 5 A comparison chart of active power loss before and after optimizing the operation mode of the distribution transformer. Detailed Implementation

[0044] The technical solutions of the embodiments of the present invention will now be described with reference to the accompanying drawings.

[0045] Example 1.

[0046] A power system contains a large number of transformers, and the operating status of these transformers is a crucial factor in ensuring the overall efficiency of the power system. For multiple transformers operating in parallel, due to load variations, it is necessary to optimize the economical operation of these transformers to reduce power losses.

[0047] This embodiment uses a power system consisting of two distribution transformers as an example, with two distribution transformers installed in one distribution room. When the transformer load in the distribution room is very low, the efficiency of the operating transformer is kept close to its maximum value by optimizing the timing of disconnecting one transformer, thereby achieving energy saving of the distribution transformer. The optimal operating efficiency of the distribution transformer can be reflected by the optimal economic operating level of the distribution transformer.

[0048] like Figure 1 As shown in the figure, a control method for optimizing the operation of a distribution transformer in this embodiment includes the following steps:

[0049] Step S1: Determine whether the load rate of the currently operating distribution transformer is lower than the optimal load rate value; the load rate is the ratio of the actual capacity of the transformer to its rated capacity.

[0050] Step S2: If so, establish a power loss model for the distribution transformer, aiming to minimize the power loss of the distribution transformer, and obtain the minimum load rate; adjust the operating state of the distribution transformer to make the load rate close to the optimal load rate.

[0051] Step S3: Measure the actual value of no-load loss, measure the inferred value of no-load loss, and measure the short-circuit loss value.

[0052] Step S4: Considering the actual operating voltage, the service life of the distribution transformer, the time when the distribution transformer is connected to the distribution network, and the power load plan, establish an energy loss model for the distribution transformer to obtain the optimal load value and the best long-term load rate.

[0053] Step S5: Adjust the operating status of the distribution transformer according to the optimal long-term load rate through the intelligent switching control device.

[0054] The specific steps are as follows:

[0055] The optimal operating efficiency of a transformer can be represented by its optimal economic operating level, which can be expressed by the following formula:

[0056]

[0057] Among them, S B S represents the rated capacity of the transformer. OPT The optimal capacity for economical operation of the transformer; ΔP NL For the no-load loss of the transformer; ΔP SL This refers to the short-circuit loss of the transformer.

[0058] Define the optimal load factor k of the transformer. L The ratio of a transformer's optimal load to its rated capacity can be expressed by the following formula:

[0059]

[0060] When calculating using equations (1) and (2), the ratio of no-load loss to short-circuit loss of these transformers varies between 3.3 and 5.0, and the load factor of the transformers varies between 0.45 and 0.55. Typically, during the transformer design phase, the transformer's maximum load is used to determine its load-carrying capacity. Therefore, the currently operating power transformers have a lower load factor than the optimal load factor, and most of them are operating under suboptimal conditions.

[0061] The power loss of a distribution transformer can be determined by the following formula:

[0062]

[0063] Where U is the actual voltage at the high-voltage side port of the transformer, in kV; U B This is the rated voltage at the high-voltage side of the transformer. In reality, the transformer's energy loss is determined by both the transformer's operating time and the shape factor of the load plan, specifically expressed by the following formula:

[0064]

[0065] Among them, T Y τ is the annual operating time of the transformer, expressed in hours; τ is the operating time of the transformer at maximum power loss, determined by the actual planned load value or the number of maximum load hours, also expressed in hours. Specifically, it is expressed by the following formula:

[0066] τ=LSF·T (5)

[0067]

[0068] Where LSF is the load loss factor, with coefficient k taking a value of 0.33 and T taking a value of 8760 hours.

[0069] Throughout the year, a transformer experiences its minimum power loss when operating under conditions where no-load loss and short-circuit loss are equal. This is considering the load planning time T. Y The power loss time τ and its corresponding minimum power loss, when U = UB, yield the following optimal load for the transformer:

[0070]

[0071] Comparing equations (1) and (7), it can be seen that when considering the average value of the maximum load, the calculated optimal load value indicates that the on-load tap changer needs a higher load than in actual operation.

[0072] In some cases, when the total load is SL, shutting down part of the transformer is more economical. During transformer operation, the cost-effective load is defined as S. EC,ΔP The transformer load is most favorable within this range. When the load changes from zero to S... EC,ΔP The operation of a transformer is appropriate. When the load is higher than S... EC,ΔP At that time, parallel operation of two transformers is more economical and efficient.

[0073] When the transformer load is S EC,ΔP If the power loss of one transformer is equal to the power loss of two transformers operating in parallel, then it is best to disconnect one of the transformers. EC,ΔP The expression is as follows:

[0074]

[0075] When both the transformer start-up time and the power load plan are considered, the load S' in this case is determined by analogy formula (8) based on the principle that the power loss during the operation of one and two transformers is equal. EC,ΔP The specific expression is as follows:

[0076]

[0077] Specifically, during the lifespan of a power transformer, its electromagnetic characteristics gradually change, and its no-load loss ΔPNL increases with the number of years of operation. Therefore, when calculating the power loss of a power transformer, it is recommended to use the actual no-load loss value measured under operating conditions. For distribution transformers with a service life exceeding 20 years, calculate their no-load loss ΔP... NLP It should increase by 1.75% every year for more than 20 years of operation.

[0078] ΔP NL,LT =ΔP NL [1+0.0175(T LT -20)] (10)

[0079] Among them, T LT This represents the service life of the transformer, expressed in years.

[0080] Then, by combining equations (2), (4), (7), and (10), the optimal long-term load factor for distribution transformers operating for more than 20 years can be obtained as follows:

[0081]

[0082] Disconnecting some transformers for economic reasons is permitted, provided that it does not affect the reliability of the power supply to users.

[0083] Therefore, intelligent switching control devices can be installed in the power distribution room to achieve intelligent operation of transformer switching. To reduce the number of switching operations, the transformer switching frequency issued by the automatic switching control device should not exceed 2-3 times / day. In addition, the transformer load determined by equations (9) and (11) should not exceed 75% of the allowable load.

[0084] Example 2.

[0085] This embodiment is an optimized control method for the operation of a distribution transformer based on Embodiment 1. Based on equations (3) and (4) of Embodiment 1, a relationship diagram between transformer power, power loss, and load can be obtained, as follows: Figure 2 The graphs shown depict the relationship between minimum power loss and energy loss and transformer power, illustrating the power of the two transformers obtained from equations (3) and (4), and the relationship between the power and energy loss of the power transformers in a dual-transformer substation and the load power on the low-voltage bus SL, obtained from equations (3) and (4). ΔP1 and ΔW1 represent the power and energy loss of one transformer during operation, respectively; ΔP2 and ΔW2 represent the power and energy loss of both transformers during operation, respectively.

[0086] Analysis of the relationship between ΔP(SL) and ΔW(SL) shows that when considering the transformer start-up time and the actual power load plan, the economic power of the transformer changes in the direction of its increase. When using formula (9) for calculation, the range of optimal operating power of the transformer will increase. In this case, the operating time of a distribution room with a single transformer under uneven load plans will increase. Due to the no-load loss of the transformer that is not disconnected, the power loss of the transformer is reduced.

[0087] Suppose a power distribution room consists of two double-winding distribution transformers, transformer #1 and transformer #2, both with a rated capacity of 1000kVA; their no-load loss and short-circuit loss are 0.889kW and 2.778kW, respectively.

[0088] When considering both the transformer start-up time and the power load plan, the optimal load S of the transformer can be obtained using equation (7). OPT It is 565.5kW; take T Y =1.2τ, then the cost-benefit load calculated using formula (9) is S' EC,ΔP The total load is 873kW. This means that when the total load of the distribution room is between 0-873kW, a single transformer operates; when the total load exceeds 873kW, two transformers operate in parallel. The total load variation in the distribution room throughout the day in this scenario is SL. The comparison of the operating modes of the two transformers before and after optimization, as well as the active power loss, are as follows: Figure 3 , Figure 4 As shown. Figure 3 This is a diagram showing the total load of the power distribution room and the operation of the power distribution transformers before optimization. Figure 4 This is a diagram showing the total load of the power distribution room and the optimized operation of the power distribution transformer.

[0089] Figure 3 The text indicates that the operation mode of the two distribution transformers in the power distribution room has not been optimized. The load SL represents the total load of the power distribution room during the day. The bar chart represents the operation mode of the two distribution transformers. When the operation mode value is 1, it means that distribution transformer #1 is in operation. When the operation mode value is 2, it means that distribution transformer #2 is in operation. When the operation mode value is 3, it means that distribution transformer #1 and distribution transformer #2 are operating in parallel.

[0090] Figure 4 The figure represents the result obtained by using the transformer operation mode optimization control method of this embodiment. The load SL represents the total load of the substation during the day. The bar chart represents the operation mode of the two transformers. When the operation mode value is 1, it means that transformer #1 is in operation. When the operation mode value is 2, it means that transformer #2 is in operation. When the operation mode value is 3, it means that transformer #1 and transformer #2 are operating in parallel.

[0091] Figure 3 and Figure 4 Compare active power loss, such as Figure 5 As shown, Figure 5 A comparison chart of active power losses before and after optimizing the operation mode of the distribution transformer. Analysis Figure 5 It can be seen that by adopting the transformer operation mode optimization control method proposed in this embodiment, the active power loss during transformer operation can be reduced, thereby ensuring the efficiency of optimized and coordinated operation of multiple transformers in the power distribution room.

[0092] In summary, the control method for optimizing the operation of distribution transformers proposed in this invention can significantly reduce the power loss and energy loss of distribution transformers in distribution rooms with seasonal load changes, thus having significant implications for improving the operating efficiency of distribution network transformers.

Claims

1. An intelligent switching control method for optimizing the operation of multiple distribution transformers, characterized in that, Includes the following steps: S1: Determine whether the load rate of the currently operating distribution transformer is lower than the optimal load rate value; S2: If so, establish a power loss model for the distribution transformer, aiming to minimize the power loss of the distribution transformer, and obtain the minimum load rate; adjust the operating state of the distribution transformer to make the load rate close to the optimal load rate. Power loss model accounting for actual high voltage , high voltage rated voltage , and optimal load ratio ; S3: Measure the actual value of no-load loss, measure the inferred value of no-load loss, and measure the short-circuit loss value; The no-load loss estimation value only considers distribution transformers with a service life of more than 20 years, calculating the no-load loss for each year of operation of the transformer over 20 years, with an increase of 1.75%; the model is: , no-load loss of the transformer; service life of the transformer; S4: Simultaneously considering the actual operating voltage, the service life of the distribution transformer, the time the distribution transformer is connected to the distribution network, and the power load plan, establish an energy loss model for the distribution transformer to obtain the optimal load value and the optimal long-term load rate; the optimal long-term load rate should not exceed 75% of the allowable value; Energy loss model is determined by the annual run time of the distribution transformer and the form factor of the load schedule, the maximum power loss run time of the transformer determined; Maximum power loss run time Determined from actual load plan values or from maximum load hours, for: LSF It is the load loss factor, coefficient. k The value is 0.

33. T The value is 8760 hours; When considering both the transformer start-up time and the actual power load plan, the economic power of the transformer changes in the direction of increasing, and the range of the transformer's optimized operating power also increases. S5: Based on the optimal long-term load rate, the operating status of the distribution transformer is adjusted through an intelligent switching control device, thereby reducing the active power loss during the operation of the distribution transformer.

2. The intelligent switching control method for optimizing the operation of multiple distribution transformers according to claim 1, characterized in that, The optimal load factor of the distribution transformer mentioned in step S1 is: Optimal load factor of distribution transformer The ratio of the optimal load to the rated capacity of a distribution transformer is expressed by the following formula: in, This refers to the rated capacity of the transformer; The optimal capacity for economical operation of the transformer; This refers to the no-load loss of the transformer; This refers to the short-circuit loss of the transformer.

3. The intelligent switching control method for optimizing the operation of multiple distribution transformers according to claim 1, characterized in that, The power loss model of the distribution transformer mentioned in step S2 is as follows: in, This is the actual voltage at the high-voltage side port of the transformer, in kV. It is the rated voltage of the high-voltage side port of the transformer.

4. The intelligent switching control method for optimizing the operation of multiple distribution transformers according to claim 1, characterized in that, The energy loss model of the distribution transformer mentioned in step S4 is as follows: in, This refers to the transformer's annual operating time, expressed in hours. This is the time the transformer operates at its maximum power loss, expressed in hours.

5. The intelligent switching control method for optimizing the operation of multiple distribution transformers according to claim 4, characterized in that, The optimal load value mentioned in step 4 is the optimal capacity for economical operation of the transformer, which is: in, The optimal capacity for economical operation of the transformer; This refers to the rated capacity of the transformer; This refers to the no-load loss of the transformer; This refers to the short-circuit loss of the transformer. This refers to the annual operating time of the transformer; This is the time during which the transformer operates at its maximum power loss.

6. The intelligent switching control method for optimizing the operation of multiple distribution transformers according to claim 1, characterized in that, The optimal long-term load factor described in step S4 is: in, This is the actual voltage at the high-voltage side port of the transformer, in kV. It is the rated voltage at the high-voltage side port of the transformer; This is the inferred value of no-load loss; This refers to the short-circuit loss of the transformer; This is the time during which the transformer operates at its maximum power loss.

7. A smart switching control method for optimizing the operation of multiple distribution transformers according to any one of claims 1 to 6, characterized in that, Step S5 specifically involves the intelligent switching control device controlling multiple distribution transformers to start or stop operation.

8. The intelligent switching control method for optimizing the operation of multiple distribution transformers according to claim 7, characterized in that, The ratio of no-load loss to short-circuit loss of distribution transformers varies between 3.3 and 5.0, and the load factor of distribution transformers varies between 0.40 and 0.55.

Images