Optical storage flexible railway power supply system and method based on energy router

Abstract

The invention discloses an optical storage flexible railway power supply system and method based on an energy router. Existing electrified railway traction power supply systems basically adopt three-phase and two-phase power supply modes. The energy router provided by the invention comprises two single-phase AC-DC (Alternating Current-Direct Current) converters and a three-phase AC-DC converter, the two single-phase AC-DC converters are respectively connected with a secondary side of the step-down transformer, a primary side of the step-down transformer is connected with an AC left side power supply arm and an AC right side power supply arm, an AC port of the three-phase AC-DC converter is connected with a 10kV power distribution network, the three converters share a DC port, and the super capacitor serves as energy storage and is connected to the DC port of the converter through the bidirectional DC-DC converter; the photovoltaic system is connected to a 10kV power grid through the DC-AC converter, and the plurality of converters and the photovoltaic system are respectively connected to a line in a distributed manner. According to the invention, power scheduling between a 27.5 kV system and a 10 kV system and negative sequence and network voltage fluctuation electric energy quality comprehensive treatment are realized.

Description

Technical Field

[0001] The present invention belongs to the technical field of traction power supply, and specifically relates to a photovoltaic storage flexible railway power supply system and method based on an energy router. Background Art

[0002] At present, the existing electrified railway traction power supply systems at home and abroad basically adopt three-phase and two-phase (out-of-phase) power supply modes. The substation takes power from the three-phase power grid through the traction transformer and steps down the voltage, and then outputs it in two power supply arms to supply power to the traction network. With the rapid development of high-speed railways and heavy-load railways in recent years, the single-phase load of the existing traction power supply system is reflected to the three-phase power grid, which will generate negative sequence current, resulting in three-phase voltage imbalance. The increase in the traction power of high-speed and heavy-load trains makes the negative sequence problem more prominent, and the high-power traction and braking of locomotives will also cause the traction network voltage to fluctuate violently. Secondly, due to the existence of the electrical phase separation device, it is difficult to achieve energy interconnection and cross-regional power supply between the existing traction substations, and the excess regenerative braking energy of the system cannot be fully utilized. At the same time, the station's 10kV distribution network also has a network voltage fluctuation problem due to load fluctuations. Therefore, it is a future development trend to solve the above problems through energy routers, interconnect the 27.5kV and 10kV systems, centrally manage the energy of the two systems, and comprehensively manage their power quality problems.

[0003] However, in order to efficiently utilize the energy of the two systems and improve energy utilization while meeting the power quality requirements, an effective control method is needed to coordinate power transmission. Chinese patent CN114285066B discloses a power balancing coordination control method and system for a multi-terminal flexible interconnected distribution system. By adjusting the power exchange of each port of the flexible direct current interconnection device, load balancing of each power source of the AC distribution line is achieved, but the consideration of power quality is lacking, and the problems of system negative sequence and network voltage fluctuation are not solved. Chinese patent CN116683519B discloses an optimized operation control method for a photovoltaic storage flexible railway power supply system, which uses a local controller to locally control the flexible traction transformer, and uses a secondary controller to correct the local control result. It solves the problems of reactive power distribution and line loss optimization that have not been fully solved in the prior art in the grid-connected operation of flexible traction transformers. The above control method does not take the system operating cost as the optimization target, and there is still a lot of room for improvement in economic cost. At the same time, it does not consider the energy optimization scheduling problem of the two systems. Summary of the invention

[0004] In order to make up for the shortcomings of the prior art, the present invention provides a photovoltaic storage flexible railway power supply system and method based on an energy router, which utilizes the charging and discharging of the energy storage system and the power transmission of the energy router to perform power scheduling between the 27.5kV and 10kV systems, and realizes comprehensive management of negative sequence and grid voltage fluctuation power quality, which is of great significance to the development of the railway network and energy conservation and emission reduction.

[0005] In order to achieve the above object, the technical solution adopted by the present invention is:

[0006] A solar-storage flexible railway power supply system based on an energy router, comprising an energy router installed in an AC traction substation, wherein the energy router comprises two single-phase AC-DC converters and one three-phase AC-DC converter;

[0007] Two single-phase AC-DC converters are connected to the secondary side of the step-down transformer respectively. The primary side of the step-down transformer is connected to the left and right AC power supply arms. The AC port of the three-phase AC-DC converter is connected to the 10kV distribution network. The three converters share one DC port. The supercapacitor is connected to the converter DC port through a bidirectional DC-DC converter as energy storage. The photovoltaic system is connected to the 10kV power grid through a DC-AC converter. Multiple converters and photovoltaic systems are connected in a distributed manner on the line.

[0008] An optimized operation control method of a photovoltaic energy storage flexible railway power supply system based on an energy router comprises the following steps:

[0009] Step 1: Collect the voltage U of the power supply arms on both sides of 27.5kV L,α , U L,β and current I L,α , I L,β , collect 10kV system voltage U L,10 and current I L,10 , the system load power P is calculated at this time L,α , P L,β , P L,10 and negative sequence VU;

[0010] Step 2: Based on the current operating conditions, determine whether the negative sequence and grid voltage exceed the standard. If so, calculate the minimum converter capacity S required to compensate the system negative sequence and grid voltage to within the national standard limit. iAC-DC,DQ , (i=α,β,10); if none of them exceeds the standard, the converter capacity required for power quality compensation is S iAC-DC,DQ =0,(i=α,β,10);

[0011] Step 3: Enter the capacity limit E of the supercapacitor s,rate and the rated power P of the supercapacitor s,rate , after inputting the compensated power quality of the AC-DC converter, the remaining rated capacity is:

[0012] S iAC-DC,res =S iAC-DC,cap -S iAC-DC,DQ ,(i=α,β,10); (9)

[0013] Step 4: Calculate the two-part power construction costs required for the operation of the 27.5kV and 10kV systems, and establish the objective function for optimal operation;

[0014] Step 5: Based on the post-compensation load data and the parameters obtained in step 3, establish the constraints for optimal operation, including active power balance constraints, hybrid energy storage dynamic energy storage constraints, energy feedback device constraints, and converter capacity constraints;

[0015] Step 6: Based on the objective function established in step 4 and the constraints established in step 5, a linear optimization model is established, and the CPLEX solver is used to solve the optimal daily operation plan for the transmission power of each converter of the energy router and the energy storage charging and discharging power, as well as the daily minimum electricity charges for the 27.5kV and 10kV systems.

[0016] Furthermore, the specific method for determining whether the negative sequence and grid voltage exceed the standard in step 2 is as follows:

[0017]

[0018] U L,low L,α ,U L,β L,high (2)

[0019] U L,10low L,10 L,10high (3)

[0020] Among them, K is the traction transformer ratio, U S is the grid-side line voltage, S is the system short-circuit capacity, U L,low ,U L,high The upper and lower limits of the voltage are 27.5kV, U L,10low ,U L,10high The upper and lower limits of the voltage are 10kV;

[0021] The specific method for calculating the minimum converter capacity required to compensate the system negative sequence and grid voltage to within the national standard limit is as follows:

[0022]

[0023] S iAC-DC,DQ =U c,i I c,i =P c,i +jQ c,i ,(i=α,β,10)(8)

[0024] Among them, U c,i ,I c,i (i=α,β,10) is the voltage and compensation current of the current transformer, P c,i ​​​​,Q c,i (i=α,β,10) is the active and reactive power that the converter needs to transmit to compensate for negative sequence and grid voltage, U` L,i (i=α,β,10) is the voltage after compensation, R i ,X i (i=α,β,10) are the line resistance and reactance.

[0025] Furthermore, the objective function in step 4 includes the electricity price cost and the energy storage device operation and maintenance cost, which is as follows:

[0026] minf 0 =C grid +C dem +C ESS (10)

[0027] Where: C grid The sum of electricity charges; C dem is the sum of the demand charges, C ESS Operation and maintenance costs of energy storage devices;

[0028]

[0029] Among them, c buy，t The purchase price is based on the time-of-use electricity price. 27.5gridbuy,t P is the electric power obtained by the 27.5kV AC traction substation from the power grid; 10gridbuy,t The output power of 10kV; c fed，t P is the price of feeding back electric energy from the traction substation to the grid; 27.5gridfed,t The electric power fed back to the grid from the 27.5kV AC traction substation;

[0030] C dem =[max(P 27.5dem,t )+max(P 10dem,t )]·c dem / N day (12)

[0031] Where P 27.5dem,t The power required for 27.5kV AC traction substation; P 10dem,t is the required power of the 10kV system, and the calculation methods of the two are:

[0032]

[0033] Formula (12) is the calculation formula for the sum of the demand electricity charges of 27.5kV and 10kV systems, c dem is the demand electricity price; N day The number of days per month that the system operates, usually 30;

[0034]

[0035] where c s，t P is the operation and maintenance cost of supercapacitor; sch，t and P sdis，t are the charging and discharging power of the supercapacitor respectively.

[0036] Furthermore, the constraints in step 5 include active power balance constraints, energy storage constraints and converter capacity constraints, which are as follows:

[0037] Active power balance constraints:

[0038] P 27.5gridbuy，t -P 27.5gridfed，t =P L，α +P c，α +P L，β +P c，β (16)

[0039] P 10gridbuy,t +P PV =P L,10 +P c,10 (17)

[0040] P sdis,t +P sch,t =P c,α +P c,β +P c,10 (18)

[0041] Energy storage constraints:

[0042]

[0043] Where E s，t Represents the energy stored in the supercapacitor; ε s Represents the self-discharge rate of the supercapacitor; η sdis Represents the discharge efficiency of the supercapacitor, η sch Indicates the charging efficiency of the supercapacitor;

[0044]

[0045] SoC s Indicates the minimum limit of the supercapacitor's allowed state of charge; Indicates the maximum limit of the supercapacitor's allowed state of charge;

[0046] 0≤P sch,t ≤(1-v s,t ) s,rate (twenty one)

[0047] Where: v s，tis a binary variable used to describe the charging or discharging state of the supercapacitor, v s，t =1 means the supercapacitor is in discharge state, v s，t =0 means the supercapacitor is in charging state;

[0048] Converter capacity constraints:

[0049] -S iAC-DC,res ≤P c,i ≤S iAC-DC,res ,(i=α,β,10).

[0050] Beneficial effects of the present invention:

[0051] 1) The present invention proposes a photovoltaic storage flexible railway power supply system structure based on an energy router. Through the access of multi-terminal power electronic converters, energy storage systems and distributed photovoltaics, the integrated power supply of the railway system is realized, breaking the energy barriers of the traditional 27.5kV and 10kV power supply systems, coordinating the power flows of the two systems, efficiently utilizing regenerative braking energy and photovoltaics, and simultaneously solving the problems of AC negative sequence, traction network voltage fluctuation and 10kV system network voltage fluctuation in the 27.5 traction power supply system;

[0052] 2) The present invention proposes an optimized operation control method for a photovoltaic energy storage flexible railway power supply system based on an energy router. It takes negative sequence and traction network voltage as constraints, gives priority to meeting the power quality requirements, and then establishes an optimized operation model with the goal of minimizing the total operating cost of the two systems. It realizes unified optimization management of power flow, maximizes the energy utilization of the system, and reduces the daily operating electricity cost of the flexible system. It has important engineering significance for the engineering practice of flexible power supply devices. BRIEF DESCRIPTION OF THE DRAWINGS

[0053] Figure 1 This is a flow chart of the operation control method of the present invention;

[0054] Figure 2 This is a schematic diagram of the structure of the power supply system of the present invention;

[0055] Figure 3 This is a comparison diagram of the output power of a 27.5kV traction substation before and after the optimization operation of the present invention;

[0056] Figure 4 This is a comparison diagram of 10kV power grid output power before and after the optimization operation of the present invention;

[0057] Figure 5 The three AC-DC converter transmission power diagrams after optimization of the present invention;

[0058] Figure 6 This is the energy storage SOC change diagram after optimization of the present invention. DETAILED DESCRIPTION

[0059] The present invention is described in detail below in conjunction with specific implementation modes.

[0060] The present invention utilizes the charging and discharging of the energy storage system and the power transmission of the energy router to perform power dispatch between the 27.5kV and 10kV systems, thereby achieving comprehensive management of negative sequence and grid voltage fluctuation power quality.

[0061] like Figure 2 As shown, the solar-storage flexible railway power supply system based on the energy router of the present invention includes an energy router installed in an AC traction substation, and the energy router includes two single-phase AC-DC converters and one three-phase AC-DC converter;

[0062] Two single-phase AC-DC converters are connected to the secondary side of the step-down transformer respectively. The primary side of the step-down transformer is connected to the left and right AC power supply arms. The AC port of the three-phase AC-DC converter is connected to the 10kV distribution network. The three converters share one DC port. The supercapacitor is connected to the DC port of the converter as energy storage through a bidirectional DC-DC converter.

[0063] The photovoltaic system is connected to the 10kV power grid through a DC-AC converter, and multiple converters and photovoltaic systems are connected in a distributed manner on the line.

[0064] The working principle of the present invention is as follows:

[0065] Because the AC traction power supply system uses a Vv transformer, it will cause three-phase asymmetry and excessive negative sequence during operation. Two single-phase AC-DC converters can balance the power of the two power supply arms and compensate for the reactive power at the same time, compensating the negative sequence to within the national standard limit; secondly, the active and reactive power generated will change the traction network flow, adjust the network voltage, and prevent the network voltage fluctuation from exceeding the limit; on the other hand, train braking will generate regenerative braking energy, which can be transmitted to the other power supply arm through the AC-DC converter, or transmitted to the 10kV system for use, or transmitted to the supercapacitor as energy storage. When the system is at peak load, the supercapacitor discharges and shares part of the power for the system; adding a photovoltaic system to the 10kV system can save energy and reduce emissions for the system. When the photovoltaic power exceeds the power required by the 10kV system, the remaining power is transmitted to the 27.5kV through the energy router for the locomotive.

[0066] like Figure 1 As shown, the operation control method of the present invention comprises the following steps:

[0067] Step 1: Collect the voltage U of the power supply arms on both sides of 27.5kV L,α , U L,β and current I L,α , I L,β , collect 10kV system voltage U L,10and current I L,10 , the system load power P is calculated at this time L,α , P L,β , P L,10 and negative sequence VU;

[0068] In step 1, the specific method for calculating the system load power and negative sequence is as follows:

[0069] P L，α =U L，α ×I L，α

[0070] P L，β =U L，β ×I L，β

[0071] P L，10 =U L，10 ×I L，10

[0072]

[0073] Step 2: Based on the current operating conditions, determine whether the negative sequence and grid voltage exceed the standard. If so, calculate the minimum converter capacity S required to compensate the system negative sequence and grid voltage to within the national standard limit. iAC-DC,DQ , (i=α,β,10); if none of them exceeds the standard, the converter capacity required for power quality compensation is S iAC-DC,DQ =0,(i=α,β,10);

[0074] In step 2, the specific method for judging whether the negative sequence and grid voltage exceed the standard is as follows:

[0075]

[0076] U L,low L,α ,U L,β L,high (2)

[0077] U L,10low L,10 L,10high (3)

[0078] Among them, K is the traction transformer ratio, U S is the grid-side line voltage, S is the system short-circuit capacity, U L,low ,U L,high The upper and lower limits of the voltage are 27.5kV, U L,10low ,U L,10high The upper and lower limits of the voltage are 10kV;

[0079] ​​​​In step 2, the specific method for calculating the minimum converter capacity required to compensate the system negative sequence and grid voltage to within the national standard limit is as follows:

[0080]

[0081] S iAC-DC,DQ =U c,i I c,i =P c,i +jQ c,i ,(i=α,β,10)(8)

[0082] Among them, U c,i ,I c,i (i=α,β,10) is the voltage and compensation current of the current transformer, P c,i ,Q c,i (i=α,β,10) is the active and reactive power that the converter needs to transmit to compensate for negative sequence and grid voltage, U` L,i (i=α,β,10) is the voltage after compensation, R i ,X i (i=α,β,10) are the line resistance and reactance.

[0083] The formula is used to calculate the active and reactive power that the converter needs to transmit, change the current of the traction network, and adjust the network voltage. At the same time, it also changes the current of the three-phase power grid and compensates for the negative sequence.

[0084] Step 3: Enter the capacity limit E of the supercapacitor s,rate and the rated power P of the supercapacitor s,rate , after inputting the compensated power quality of the AC-DC converter, the remaining rated capacity is:

[0085] S iAC-DC,res =S iAC-DC,cap -S iAC-DC,DQ ,(i=α,β,10) (9)

[0086] Step 4: Calculate the two-part power construction costs required for the operation of the 27.5kV and 10kV systems, and establish the objective function for optimal operation;

[0087] The objective function in step 4 includes the electricity price cost and the operation and maintenance cost of the energy storage device, as follows:

[0088] minf 0 =C grid +C dem +C ESS (10)

[0089] Where: C grid The sum of electricity charges; C dem is the sum of the demand charges, C ESSIt is the operation and maintenance cost of the energy storage device.

[0090]

[0091] Among them, c buy，t The purchase price is based on the time-of-use electricity price. 27.5gridbuy,t P is the electric power obtained by the 27.5kV AC traction substation from the power grid; 10gridbuy,t The output power of 10kV; c fed，t P is the price of feeding back electric energy from the traction substation to the grid; 27.5gridfed,t The electric power fed back to the grid from the 27.5kV AC traction substation.

[0092] C dem =[max(P 27.5dem,t )+max(P 10dem,t )]·c dem / N day (12)

[0093] Where P 27.5dem,t The power required for 27.5kV AC traction substation; P 10dem,t is the required power of the 10kV system, and the calculation methods of the two are:

[0094]

[0095] Formula (12) is the calculation formula for the sum of the demand electricity charges of 27.5kV and 10kV systems, where P 27.5dem,t P is the power required for AC traction substation; 10dem,t is the power required for DC traction substation; c dem is the demand electricity price; N day The number of days per month that the system is in operation, usually 30.

[0096]

[0097] where c s，t P is the operation and maintenance cost of supercapacitor; sch，t and P sdis，t are the charging and discharging power of the supercapacitor respectively.

[0098] Step 5: Based on the compensated load data and the parameters obtained in step 3, establish the constraints for the optimal operation;

[0099] The constraints in step 5, including power balance constraints, energy storage constraints and converter capacity constraints, are as follows:

[0100] Power balance constraints:

[0101] P27.5gridbuy，t -P 27.5gridfed，t =P L，α +P c，α +P L，β +P c，β (16)

[0102] P 10gridbuy,t +P PV =P L,10 +P c,10 (17)

[0103] P sdis,t +P sch,t =P c,α +P c,β +P c,10 (18)

[0104] Energy storage constraints:

[0105]

[0106] Where E s，t Represents the energy stored in the supercapacitor; ε s Represents the self-discharge rate of the supercapacitor; η sdis Represents the discharge efficiency of the supercapacitor, η sch Indicates the charging efficiency of the supercapacitor.

[0107]

[0108] SoC s Indicates the minimum limit of the supercapacitor's allowed state of charge; Indicates the maximum limit of the supercapacitor's allowed state of charge.

[0109] 0≤P sch,t ≤(1-v s,t ) s,rate (twenty one)

[0110] Where: v s，t is a binary variable used to describe the charging or discharging state of the supercapacitor, v s，t =1 means the supercapacitor is in discharge state, v s，t =0 means the supercapacitor is in charging state.

[0111] Converter capacity constraints:

[0112] -S iAC-DC,res ≤P c,i ≤S iAC-DC,res ,(i=α,β,10)

[0113] Step 6: Based on the objective function established in step 4 and the constraints established in step 5, a linear optimization model is established, and the CPLEX solver is used to solve the optimal daily operation plan for the transmission power of each converter of the energy router and the energy storage charging and discharging power, as well as the daily minimum electricity charges for the 27.5kV and 10kV systems.

[0114] like Figure 3-6 As shown, the present invention realizes integrated power supply of the railway system through the access of multi-terminal power electronic converters, energy storage systems and distributed photovoltaics, breaks the energy barriers of traditional 27.5kV and 10kV power supply systems, coordinates the power flow of the two systems, efficiently utilizes regenerative braking energy and photovoltaics, and simultaneously solves the problems of AC negative sequence, traction network voltage fluctuations and 10kV system network voltage fluctuations in the 27.5 traction power supply system.

[0115] The content of the present invention is not limited to the embodiments listed, and any equivalent changes made to the technical solution of the present invention by ordinary technicians in this field after reading the description of the present invention are covered by the claims of the present invention.

Claims

1. A solar energy storage flexible railway power supply system based on energy router, characterized by: An energy router installed in an AC traction substation includes two single-phase AC-DC converters and one three-phase AC-DC converter; Two single-phase AC-DC converters are connected to the secondary side of the step-down transformer respectively. The primary side of the step-down transformer is connected to the left and right AC power supply arms. The AC port of the three-phase AC-DC converter is connected to the 10kV distribution network. The three converters share one DC port. The supercapacitor is connected to the DC port of the converter as energy storage through a bidirectional DC-DC converter. The photovoltaic system is connected to the 10kV power grid through a DC-AC converter, and multiple converters and photovoltaic systems are connected in a distributed manner on the line.

2. An optimized operation control method for a photovoltaic energy storage flexible railway power supply system based on an energy router, characterized in that: The following steps are involved: Step 1: Collect the voltage U of the power supply arms on both sides of 27.5kV L,α , U L,β and current I L,α , I L,β , collect 10kV system voltage U L,10 and current I L,10 , the system load power P is calculated at this time L,α , P L,β , P L,10 and negative sequence VU; Step 2: Based on the current operating conditions, determine whether the negative sequence and grid voltage exceed the standard. If so, calculate the minimum converter capacity S required to compensate the system negative sequence and grid voltage to within the national standard limit. iAC-DC,DQ , (i=α,β,10); if none of them exceeds the standard, the converter capacity required for power quality compensation is S iAC-DC,DQ =0,(i=α,β,10); Step 3: Enter the capacity limit E of the supercapacitor s,rate and the rated power P of the supercapacitor s,rate , after inputting the compensated power quality of the AC-DC converter, the remaining rated capacity is: S iAC-DC,res =S iAC-DC,cap -S iAC-DC,DQ ,(i=α,β,10); (9) Step 4: Calculate the two-part power construction costs required for the operation of the 27.5kV and 10kV systems, and establish the objective function for optimal operation; Step 5: Based on the post-compensation load data and the parameters obtained in step 3, establish the constraints for optimal operation, including active power balance constraints, hybrid energy storage dynamic energy storage constraints, energy feedback device constraints, and converter capacity constraints; Step 6: Based on the objective function established in step 4 and the constraints established in step 5, a linear optimization model is established, and the CPLEX solver is used to solve the optimal daily operation plan for the transmission power of each converter of the energy router and the energy storage charging and discharging power, as well as the daily minimum electricity charges for the 27.5kV and 10kV systems.

3. According to claim 2, the optimization operation control method of the photovoltaic energy storage flexible railway power supply system based on the energy router is characterized by: The specific method for determining whether the negative sequence and grid voltage exceed the standard in step 2 is as follows: IN L,low L,α ,IN L,β L,high (2)​​ IN L,10low L,10 L,10high (3)​​ Among them, K is the traction transformer ratio, U S is the grid-side line voltage, S is the system short-circuit capacity, U L,low ,U L,high The upper and lower limits of the voltage are 27.5kV, U L,10low ,U L,10high The upper and lower limits of the voltage are 10kV; The specific method for calculating the minimum converter capacity required to compensate the system negative sequence and grid voltage to within the national standard limit is as follows: S iAC-DC,DQ =U c,i I c,i =P c,i +jQ c,i ,(i=α,β,10)(8) Among them, U c,i ,I c,i (i=α,β,10) is the voltage and compensation current of the current transformer, P c,i ,Q c,i (i=α,β,10) is the active and reactive power that the converter needs to transmit to compensate for negative sequence and grid voltage, U` L,i (i=α,β,10) is the voltage after compensation, R i ,X i (i=α,β,10) are the line resistance and reactance.

4. According to claim 2, the optimization operation control method of the photovoltaic energy storage flexible railway power supply system based on the energy router is characterized by: The objective function in step 4 includes the electricity price cost and the energy storage device operation and maintenance cost, which is as follows: minf0=C grid +C dem +C ESS (10) Where: C grid The sum of electricity charges; C dem is the sum of the demand charges, C ESS Operation and maintenance costs of energy storage devices; Among them, c buy，t The purchase price is based on the time-of-use electricity price. 27.5gridbuy,t P is the electric power obtained by the 27.5kV AC traction substation from the power grid; 10gridbuy,t The output power of 10kV; c fed，t P is the price of feeding back electric energy from the traction substation to the grid; 27.5gridfed,t The electric power fed back to the grid from the 27.5kV AC traction substation; C dem =[max(P 27.5dem,t )+max(P 10dem,t )]·c dem / N day (12) Where P 27.5dem,t The power required for 27.5kV AC traction substation; P 10dem,t is the required power of the 10kV system, and the calculation methods of the two are: Formula (12) is the calculation formula for the sum of the demand electricity charges of 27.5kV and 10kV systems, c dem is the demand electricity price; N day The number of days per month that the system operates, usually 30; where c s，t P is the operation and maintenance cost of supercapacitor; sch，t and P sdis，t are the charging and discharging power of the supercapacitor respectively.

5. According to claim 2, the optimization operation control method of the photovoltaic energy storage flexible railway power supply system based on the energy router is characterized by: The constraints in step 5 include active power balance constraints, energy storage constraints and converter capacity constraints, which are as follows: Active power balance constraints: P 27.5gridbuy，t -P 27.5gridfed，t =P L，α +P c，α +P L，β +P c，β (16) P 10gridbuy,t +P PV =P L,10 +P c,10 (17) P sdis,t +P sch,t =P c,α +P c,β +P c,10 (18) Energy storage constraints: Where E s，t Represents the energy stored in the supercapacitor; ε s Indicates the self-discharge rate of the supercapacitor; η sdis Represents the discharge efficiency of the supercapacitor, η sch Indicates the charging efficiency of the supercapacitor; SoC s Indicates the minimum limit of the supercapacitor's allowed state of charge; Indicates the maximum limit of the supercapacitor's allowed state of charge; 0≤P sch,t ≤(1-v s,t )P s,rate (21) Where: v s，t is a binary variable used to describe the charging or discharging state of the supercapacitor, v s，t =1 means the supercapacitor is in discharge state, v s，t =0 means the supercapacitor is in charging state; Converter capacity constraints: -S iAC-DC,res ≤P c,i ≤S iAC-DC,res ,(i=α,β,10).

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