Traction power supply system energy storage capacity determination method based on comprehensive utilization rate

Abstract

The invention provides a traction power supply system energy storage capacity determination method based on a comprehensive utilization rate. The traction power supply system energy storage capacity determination method comprises the following steps: S1, determining working conditions of a traction power supply system and charge states of an energy storage system under different working conditions; s2, determining the comprehensive utilization rate of regenerative braking energy of the traction power supply system under different working conditions and different capacity configurations; s3, the regenerative braking energy comprehensive utilization rate, the power of the energy storage system and the rated capacity of the energy storage system are fitted to form a curved surface, an inflection point of the curved surface is found out, and the capacity, corresponding to the inflection point, of the energy storage system is the optimal capacity; the capacity of the energy storage system is comprehensively determined based on multiple indexes such as the energy-saving effect of the traction substation, the regenerative braking energy recovery effect of the train and the charging and discharging utilization rate of the energy storage system, so that the capacity of the energy storage system can meet the requirements of a traction power supply system.

Description

Technical Field

[0001] The present invention relates to a method for determining the energy storage capacity of a power supply system, and in particular to a method for determining the energy storage capacity of a traction power supply system based on comprehensive utilization rate. Background Art

[0002] With the substantial increase in energy consumption of high-speed rail traction power supply systems, a large amount of regenerative braking energy is difficult to be effectively utilized due to the complex operating conditions of the traction power supply system. It has to be returned to the power grid or consumed in braking resistors, resulting in low energy efficiency of high-speed rail stations.

[0003] At present, existing research usually uses technical indicators such as traction system energy saving rate, regeneration failure rate, and total system energy consumption as the basis for capacity configuration when selecting energy storage capacity. However, these indicators only determine the capacity of the energy storage system from the perspective of the operating effect of the traction power supply system, and do not consider the operating effect of the energy storage device itself. Although a large-capacity energy storage system can fully recover regenerative braking energy under high braking power conditions, the operating time of this condition in the traction system is relatively short, making it difficult for the energy storage system to be fully charged for more time, resulting in idle capacity, which is not conducive to the economic operation of the energy storage system.

[0004] Therefore, in order to solve the above technical problems, it is urgent to propose a new technical means. Summary of the invention

[0005] In view of this, the purpose of the present invention is to provide a method for determining the energy storage capacity of a traction power supply system based on comprehensive utilization rate, and comprehensively determine the capacity of the energy storage system based on multiple indicators such as the energy-saving effect of the traction substation, the energy recovery effect of the train regenerative braking, and the charging and discharging utilization rate of the energy storage system, so that the capacity of the energy storage system can not only meet the needs of the traction power supply system, but also make the energy storage system more economical, and the whole process is efficient and accurate.

[0006] The present invention provides a method for determining the energy storage capacity of a traction power supply system based on comprehensive utilization rate, comprising the following steps:

[0007] S1. Determine the working conditions of the traction power supply system and the charge state of the energy storage system under different working conditions;

[0008] S2. Determine the comprehensive utilization rate of regenerative braking energy of the traction power supply system under different working conditions and different capacity configurations;

[0009] S3. The comprehensive utilization rate of regenerative braking energy, the power of the energy storage system and the rated capacity of the energy storage system are fitted to form a surface, and the inflection point of the surface is found. The capacity of the energy storage system corresponding to the inflection point is the optimal capacity.

[0010] Further, in step S1, the state of charge of the energy storage system is determined by the following method:

[0011]

[0012] Among them: SOC es (k) is the state of charge of the energy storage system of the traction power supply system at time k, SOCes(k-1) is the state of charge of the energy storage system of the traction power supply system at time k-1, T s represents the control period, P es (k) is the power of the energy storage system at time k, when P es (k)>0 indicates the discharge state. es (k) < 0 indicates charging state, Q es.n is the rated power of the energy storage system.

[0013] Further, in step S3, the comprehensive utilization rate of the regenerative braking energy is determined by the following method:

[0014]

[0015] in: is the comprehensive utilization rate of regenerative braking energy, η TS is the energy saving rate of the substation of the traction power supply system, η RBE is the train regenerative braking energy recovery rate, η ES is the average charge and discharge utilization rate of the energy storage system, η′ RBE is the maximum recovery rate of regenerative braking energy, η′ TS is the maximum energy saving rate of traction substation, η′ ES It is the maximum charge and discharge utilization rate of the energy storage system.

[0016] Furthermore, the energy saving rate η of the traction substation is determined by the following method: TS :

[0017]

[0018] Where: n is the number of times the traction substation of the traction power supply system supplies power within a set period, P T.j is the jth output power of the traction substation, E T0 is the total traction energy consumption of the train within the set period, T s Indicates the control period.

[0019] Furthermore, the train regenerative braking energy recovery rate η is determined by the following method: RBE :

[0020]

[0021] Where: m is the number of times the energy storage system is charged within a set period, P es.i is the i-th charging power of the energy storage system, E z0 It is the total braking energy generated by the train within a set period.

[0022] Furthermore, the average charge and discharge utilization rate η of the energy storage system is determined by the following method: ES :

[0023]

[0024] Where: ΔSOC es.r It is the difference in SOC before and after the rth charging or discharging of the energy storage system.

[0025] Furthermore, the operating conditions of the traction power supply system include full traction conditions, full braking conditions, equivalent traction conditions and equivalent braking conditions.

[0026] Beneficial effects of the present invention: Through the present invention, the capacity of the energy storage system is comprehensively determined based on multiple indicators such as the energy-saving effect of the traction substation, the energy recovery effect of the train regenerative braking, and the charging and discharging utilization rate of the energy storage system, so that the capacity of the energy storage system can not only meet the needs of the traction power supply system, but also make the energy storage system more economical, and the whole process is highly efficient and accurate. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] The present invention will be further described below in conjunction with the accompanying drawings and embodiments:

[0028] Figure 1 It is a flow chart of the present invention.

[0029] Figure 2 This is a topological diagram of the high-speed railway station regenerative braking energy utilization system of the present invention.

[0030] Figure 3 The power flow relationship under various working conditions.

[0031] Figure 4 is the regenerative braking energy recovery rate.

[0032] Figure 5 It is the energy saving rate of traction substation.

[0033] Figure 6 is the average charge and discharge utilization rate of the energy storage system.

[0034] Figure 7 It is the comprehensive utilization rate of regenerative braking energy. DETAILED DESCRIPTION

[0035] The present invention is further described in detail below:

[0036] The present invention provides a method for determining the energy storage capacity of a traction power supply system based on comprehensive utilization rate, comprising the following steps:

[0037] S1. Determine the working conditions of the traction power supply system and the charge state of the energy storage system under different working conditions;

[0038] S2. Determine the comprehensive utilization rate of regenerative braking energy of the traction power supply system under different working conditions and different capacity configurations;

[0039] S3. Fit the comprehensive utilization rate of regenerative braking energy, the power of the energy storage system and the rated capacity of the energy storage system to form a surface, find the inflection point of the surface, and the capacity of the energy storage system corresponding to the inflection point is the optimal capacity. By continuously changing the capacity and power configuration of the energy storage system until the maximum capacity configured with the maximum braking power of the traction power supply system in one day and the maximum recoverable braking energy is reached, then calculate the corresponding comprehensive utilization rate, and then perform the corresponding fitting, wherein the fitting is performed using MATLAB software; through the above method, the capacity of the energy storage system is comprehensively determined based on multiple indicators such as the energy-saving effect of the traction substation, the energy recovery effect of the train regenerative braking, and the charging and discharging utilization rate of the energy storage system, so that the capacity of the energy storage system can not only meet the needs of the traction power supply system, but also make the energy storage system more economical, and the whole process is efficient and accurate.

[0040] Among them: The working conditions of the traction power supply system include full traction conditions, full braking conditions, equivalent traction conditions and equivalent braking conditions, such as Figure 2 As shown in the figure, the topology of the regenerative braking energy utilization system of the high-speed railway station, in step S1, the priority of regenerative braking energy recovery is set as follows: ① absorbed by the traction train on the other power supply arm; ② stored by the energy storage system; ③ consumed by the train braking resistor. In setting the regenerative braking energy utilization link, the priority of the traction power source required by the traction train is as follows: ① the regenerative braking energy generated by the braking train on the other power supply arm; ② the regenerative braking energy stored in the energy storage system; ③ supplied from the public power grid via the traction transformer; and, according to different working conditions, the power flow relationship can be determined, such as Figure 3 As shown:

[0041] Full traction condition, that is, the trains on the α and β phase power supply arms are in traction state. At this time, the traction power supply system does not generate regenerative braking energy, and the energy storage system gives priority to providing energy for the traction trains on the two power supply arms. When the energy storage system cannot meet the load demand, the traction substation will supplement the power supply from the public power grid.

[0042] Full braking condition, that is, the trains of the α and β phase power supply arms are in braking state. At this time, the regenerative braking energy generated by the train is first stored by the energy storage system. When the energy storage system reaches the upper limit of charge, the remaining regenerative braking energy is consumed by the braking resistor.

[0043] The equivalent traction condition is that the trains of the α and β phase power supply arms are in traction and braking states respectively, and the braking train power is less than the traction train power, and the traction power supply system as a whole is in a traction energy consumption state. Among them, the braking power generated by the braking train directly supplies energy to the traction train through the railway power regulator, and the remaining power required by the traction train is provided by the energy storage system and the traction substation.

[0044] The equivalent braking condition is that the trains of the α and β phase power supply arms are in traction and braking states respectively, and the braking train power is greater than the traction train power, and there is residual regenerative braking energy in the traction power supply system. Therefore, the braking power generated by the braking train is first used to supply energy to the traction train, and the residual energy is stored by the energy storage system and consumed by the braking resistor.

[0045] In this embodiment, in step S1, the state of charge of the energy storage system is determined by the following method:

[0046]

[0047] Among them: SOC es (k) is the state of charge of the energy storage system of the traction power supply system at time k, SOCes(k-1) is the state of charge of the energy storage system of the traction power supply system at time k-1, T s represents the control period, P es (k) is the power of the energy storage system at time k, when P es (k)>0 indicates the discharge state. es (k) < 0 indicates charging state, Q es.n is the rated power of the energy storage system. In the above, the relationship between the state of charge and the power is established, and the state of charge is the ratio of the remaining capacity to the fully charged state capacity, thereby obtaining the relationship between the capacity and the power of the energy storage system.

[0048] In this embodiment, in step S3, the comprehensive utilization rate of the regenerative braking energy is determined by the following method:

[0049]

[0050] in: is the comprehensive utilization rate of regenerative braking energy, η TS is the energy saving rate of the substation of the traction power supply system, η RBE is the train regenerative braking energy recovery rate, η ES is the average charge and discharge utilization rate of the energy storage system, η′ RBE is the maximum recovery rate of regenerative braking energy, η′ TS is the maximum energy saving rate of traction substation, η′ ES It is the maximum charge and discharge utilization rate of the energy storage system.

[0051] Specifically, the energy saving rate η of the traction substation is determined by the following method: TS :

[0052]

[0053] Where: n is the number of times the traction substation of the traction power supply system supplies power within a set period, P T.j is the jth output power of the traction substation, E T0 is the total traction energy consumption of the train within the set period, T s Indicates the control period.

[0054] The train regenerative braking energy recovery rate η is determined by the following method RBE :

[0055]

[0056] Where: m is the number of times the energy storage system is charged within a set period, P es.i is the i-th charging power of the energy storage system, E z0 It is the total braking energy generated by the train within a set period.

[0057] The average charge and discharge utilization rate η of the energy storage system is determined by the following method ES :

[0058]

[0059] Where: ΔSOC es.r It is the difference in SOC before and after the rth charging or discharging of the energy storage system.

[0060] In this embodiment, Figure 4 The train regenerative braking energy recovery rate under different capacity configurations is shown. It can be seen that when the initial power and capacity configuration are 5MW and 0.5MWh, the system regenerative braking energy recovery rate is 25.46%. es.n With rated capacity Q es.n The increase of η RBE Rapidly increases, and the regenerative braking energy recovery effect is significantly improved. es.n Increased to 29.5MW, Q es.n When it increases to 3.12MWh, η RBE It can reach 90%. Then continue to increase the energy storage power and capacity configuration, η RBE The growth is slow and gradually becomes flat. When P es.n Increase to P es.max 55MW, Q es.n Increase to Q es.max When η is 6MWh, RBEIt can reach 99.92%. Therefore, as the capacity configuration increases, η RBE After increasing to a certain extent, it will tend to level off.

[0061] In this embodiment Figure 5 The energy saving rate of traction substation under different capacity configurations is shown. Figure 5 The change trend of P is the same. Under the initial power and capacity configuration, the energy saving rate of the traction substation is 5.74%. es.n , Q es.n Increased to 28MW, 3MWh, η TS Rapidly increase to 20%, then continue to increase power and capacity configuration, η TS When the regenerative braking energy recovery rate is 99.92%, the maximum energy saving rate of the system is 22.53%. This shows that the energy saving rate of the traction substation is closely related to the recovery rate of regenerative braking energy. The more regenerative braking energy the energy storage system recovers, the more traction load it can share for the traction substation under traction conditions, thus achieving energy saving of the traction substation.

[0062] In this embodiment Figure 6 The average charge and discharge utilization rate of the energy storage system under different capacity configurations is shown. It can be seen that under the initial configuration, the average charge and discharge utilization rate of the energy storage system is 54.08%, that is, during the research period, the average charge and discharge capacity of the energy storage system is about 54% of the rated capacity. es.n Certainly, with P es.n Increased to 55MW, η ES Continue to increase to 78.22%; P es.n Certainly, with Q es.n Increase to 6MWh, η ES It continues to decrease to 12.78%. es.n When it is greater than 4MWh, the average charging and discharging utilization rate of the energy storage system is less than 30%, which means that most of the time, the energy storage system is difficult to be fully charged and most of its capacity is idle, resulting in capacity waste.

[0063] In this embodiment Figure 7 The average charge and discharge utilization rate of the energy storage system under different capacity configurations is shown, and the η under different capacity configurations is comprehensively considered. RBE , η TS and η ES It can be seen that the higher the power and capacity of the energy storage system, the better the recovery of regenerative braking energy and the energy saving effect of the traction substation. However, the operating characteristics of the traction system train will also cause the large-capacity energy storage system to have idle capacity. Figure 7 The comprehensive utilization rate of regenerative braking energy determines the capacity of the energy storage system. The specific process is: Q es.n At a certain time, With Pes.n The increase of P increases rapidly, but when es.n >27.5MW, The growth rate is slow and tends to be constant. Therefore, considering the cost efficiency of energy storage configuration, the rated power of the energy storage system can be determined to be 27.5MW. es.n When Figure 7 Available, With Q es.n The increase of first increases and then decreases. es.n When it is 2.5MWh, The maximum value is 75.25%, so the rated capacity of the energy storage system is determined to be 2.5MWh.

[0064] Table 1 shows the comparison of evaluation indicators of each unit of the system under different capacity configurations. It can be seen that under the initial capacity configuration, the energy-saving effect of the traction substation and the regenerative braking energy recovery effect of the train are not good. Although the average charge and discharge utilization rate of the energy storage system is high, it also means that the charge and discharge depth of the battery is large at this time, and long-term operation will accelerate the aging and capacity decay of the battery. Under the maximum capacity configuration, the energy-saving effect of the traction substation and the regenerative braking energy recovery effect of the train are the best, but the average charge and discharge utilization rate of the energy storage system is only 22.05%. Although the large capacity configuration reduces the depth of each charge and discharge of the battery, it is difficult to fully charge the battery most of the time, resulting in idle capacity. Therefore, compared with the initial capacity configuration and the maximum capacity configuration, the energy storage system capacity determined according to the comprehensive utilization rate can make the working effect of each unit of the regenerative braking energy utilization system source-load-storage relatively good.

[0065] Table 1

[0066]

[0067] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the purpose and scope of the technical solution of the present invention, which should be included in the scope of the claims of the present invention.

Claims

1. A method for determining energy storage capacity of a traction power supply system based on comprehensive utilization rate, characterized in that: The following steps are involved: S1. Determine the working conditions of the traction power supply system and the charge state of the energy storage system under different working conditions; S2. Determine the comprehensive utilization rate of regenerative braking energy of the traction power supply system under different working conditions and different capacity configurations; S3. The comprehensive utilization rate of regenerative braking energy, the power of the energy storage system and the rated capacity of the energy storage system are fitted to form a surface, and the inflection point of the surface is found. The capacity of the energy storage system corresponding to the inflection point is the optimal capacity.

2. The method for determining the energy storage capacity of a traction power supply system based on comprehensive utilization rate according to claim 1 is characterized in that: In step S1, the state of charge of the energy storage system is determined by the following method: Among them: SOC es (k) is the state of charge of the energy storage system of the traction power supply system at time k, SOC es (k-1) is the state of charge of the energy storage system of the traction power supply system at time k-1, T s represents the control period, P es (k) is the power of the energy storage system at time k, when P es (k)>0 indicates the discharge state. es (k) < 0 indicates charging state, Q es.n is the rated power of the energy storage system.

3. The method for determining the energy storage capacity of a traction power supply system based on comprehensive utilization rate according to claim 1 is characterized in that: In step S3, the comprehensive utilization rate of the regenerative braking energy is determined by the following method: Where: η is the comprehensive utilization rate of regenerative braking energy, η TS is the energy saving rate of the substation of the traction power supply system, η RBE is the train regenerative braking energy recovery rate, η ES is the average charge and discharge utilization rate of the energy storage system, η′ RBE is the maximum recovery rate of regenerative braking energy, η′ TS is the maximum energy saving rate of traction substation, η′ ES It is the maximum charge and discharge utilization rate of the energy storage system.

4. The method for determining the energy storage capacity of a traction power supply system based on comprehensive utilization rate according to claim 3 is characterized in that: The energy saving rate η of the traction substation is determined by the following method TS : Where: n is the number of times the traction substation of the traction power supply system supplies power within a set period, P T.j is the jth output power of the traction substation, E T0 is the total traction energy consumption of the train within the set period, T s Indicates the control period.

5. The method for determining the energy storage capacity of a traction power supply system based on comprehensive utilization rate according to claim 3 is characterized in that: The train regenerative braking energy recovery rate η is determined by the following method RBE : Where: m is the number of times the energy storage system is charged within a set period, P es.i is the i-th charging power of the energy storage system, E z0 It is the total braking energy generated by the train within a set period.

6. The method for determining the energy storage capacity of a traction power supply system based on comprehensive utilization rate according to claim 3 is characterized in that: The average charge and discharge utilization rate η of the energy storage system is determined by the following method ES : Where: ΔSOC es.r It is the difference in SOC before and after the rth charging or discharging of the energy storage system.

7. The method for determining the energy storage capacity of a traction power supply system based on comprehensive utilization rate according to claim 1 is characterized in that: The operating conditions of the traction power supply system include full traction conditions, full braking conditions, equivalent traction conditions and equivalent braking conditions.

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