Bilateral traction power supply station set power flow control system and control method

Abstract

The invention discloses a bilateral traction power supply station set power flow control system and method. The control system comprises first and second power flow control units with the same structure. The first power flow control unit comprises a left side multi-winding transformer, a right side multi-winding transformer, a bidirectional DC / DC converter and energy storage equipment, and further comprises a plurality of back-to-back converters; the primary side of the left multi-winding transformer is connected to a left power supply arm of the first traction substation, and the primary side of the right multi-winding transformer is connected to a right power supply arm of the first traction substation; each secondary side of the left-side multi-winding transformer is connected to a left-side output end of one back-to-back converter, and each secondary side of the right-side multi-winding transformer is connected to a right-side output end of one back-to-back converter; the input ends of all the back-to-back converters are connected in parallel and then are connected to the energy storage equipment through the bidirectional DC / DC converter; and the input end of the back-to-back converter is also provided with a voltage stabilizing capacitor. Reasonable control over the power flow under different combination conditions of regeneration working conditions and traction working conditions of the two power supply arms is achieved.

Description

Technical Field

[0001] The present invention relates to the field of traction power supply systems, and in particular to a bilateral traction power supply group power flow control system and control method. Background Art

[0002] The terrain, geology and climate conditions in the mountainous areas of western my country are extremely complex, the external power grid is weak, there are many long and steep slopes, and the locomotive load continuously feeds high-power reverse current into the power grid, which poses a huge challenge to the safe and reliable operation and efficient operation and maintenance of the traction power supply system. For the reverse current suppression and utilization system of electrified railways, the efficient utilization of regenerative braking energy through the coordination of energy storage systems is an effective way to achieve the goal of reverse current suppression and utilization. When the system capacity is limited, how to allocate appropriate capacity to each target will seriously affect the operation effect and stability of the system. In addition, since the two substations are connected to the same power supply under the bilateral power supply system of the traction power supply system, the reverse current generated by the regenerative braking locomotive has the phenomenon of bypassing the high-voltage transmission line. Therefore, it is a key technical problem to explore the utilization of reverse current in the bilateral power supply traction power supply system and propose an efficient current control scheme and control strategy for the bilateral power supply traction power supply system of electrified railways. Summary of the invention

[0003] The purpose of the present invention is to provide a bilateral traction power supply group flow control system and control method to achieve the suppression and reuse of the reverse flow of the bilateral traction power supply system.

[0004] The technical solution for implementing the present invention is as follows:

[0005] A bilateral traction power supply group flow control system, the bilateral traction power supply group includes a first traction substation and a second traction substation; the secondary side of the V / v traction transformer of the first traction substation is respectively connected to the left and right power supply arms of the first traction substation, and the secondary side of the V / v traction transformer of the second traction substation is respectively connected to the left and right power supply arms of the second traction substation; the right power supply arm of the first traction substation is interconnected with the left power supply arm of the second traction substation; including a first flow control unit; the first flow control unit includes a left multi-winding transformer, a right multi-winding transformer, a bidirectional DC / DC converter and an energy storage device, and also includes a plurality of back-to-back converters; the primary side of the left multi-winding transformer is connected to the first traction substation The invention relates to a left power supply arm, and the primary side of the right multi-winding transformer is connected to the right power supply arm of the first traction substation; each secondary side of the left multi-winding transformer is respectively connected to the left output end of a back-to-back converter, and each secondary side of the right multi-winding transformer is respectively connected to the right output end of a back-to-back converter; after the input ends of all back-to-back converters are connected in parallel, they are connected to the energy storage device through a bidirectional DC / DC converter; a voltage stabilizing capacitor is also arranged at the input end of the back-to-back converter; and a second power flow control unit with the same structure as the first power flow control unit is also included; the primary side of the left multi-winding transformer of the second power flow control unit is connected to the left power supply arm of the second traction substation, and the primary side of the right multi-winding transformer is connected to the right power supply arm of the second traction substation.

[0006] Preferably, the AC / DC converter module of the back-to-back converter adopts H-bridge cascade or MMC cascade.

[0007] The control method of the bilateral traction power supply group power flow control system comprises:

[0008] Step 1: Collect the instantaneous voltage and current of the left and right power supply arms of the first traction substation and the second traction substation, and calculate the instantaneous power P of the left and right power supply arms of the first traction substation and the second traction substation. 1L , P 1R , P 2L , P 2R ;

[0009] Step 2, determine the current working conditions:

[0010] As P 1R <0 and P 2L <0, it is full regeneration condition;

[0011] As P 1R >0 and P 2L >0, it is full traction condition;

[0012] As P 1R <0 and P 2L >0, it is the first half regeneration condition;

[0013] As P 1R >0 and P 2L <0, it is the second half regeneration condition;

[0014] Step 3: According to the current working conditions, the active power of the left and right power supply arms of the first traction substation and the second traction substation is allocated to obtain the active power allocation reference value P′ 1L , P′ 1R , P′ 2L , P′ 2R , and the energy storage device power reference value P of the first power flow control unit and the second power flow control unit 1,ES ,P 2,ES ;

[0015] Under full regeneration conditions:

[0016] Let P′ 1R =0;

[0017] As P 1L >0 and P 1L >|P 1R |, then let P′ 1L =P 1L -|P 1R |-P 1,ES , P 1,ES =-min(P 1L -|P 1R |,P ES,max );

[0018] As P 1L >0 and P 1L <|P 1R |, then let P′ 1L =0,P 1,ES =|P 1R |-|P 1L |;

[0019] As P 1L <0 and |P 1L |+|P 1R |<P ES,max , then let P′ 1L =0,P 1,ES =|P 1L |+|P 1R |;

[0020] As P 1L <0 and |P 1L |+|P 1R |>P ES,max , then let P′ 1L =|P 1R |-|P 1L |,P1,ES =P ES,max ;

[0021] Let P′ 2L =0;

[0022] As P 2R >0 and P 2R >|P 2L |, then let P′ 2R =P 2R -|P 2L |-P 2,ES , P 2,ES =-min(P 2R -|P 2L |,P ES,max );

[0023] As P 2R >0 and P 2R <|P 2L |, then let P′ 2R =0,P 2,ES =|P 2L |-|P 2R |;

[0024] As P 2R <0 and |P 2L |+|P 2R |<P ES,max , then let P′ 2R =0,P 2,ES =|P 2R |+|P 2L |;

[0025] As P 2R <0 and |P 2L |+|P 2R |>P ES,max , then let P′ 2R =|P 2L |-|P 2R |,P 2,ES =P ES,max ;

[0026] Among them, P ES,max The maximum output power of the energy storage device of the first power flow control unit and the second power flow control unit;

[0027] Under full traction conditions:

[0028] P′ 1L =C 1,k (P 1L +P 1R +P 1,ES ), P′ 1R =(1-C1,k )(P 1L +P 1R +P 1,ES );

[0029] P′ 2L =C 2,k (P 2L +P 2R +P 2,ES ), P′ 2R =(1-C 2,k )(P 2L +P 2R +P 2,ES );

[0030] P 1,ES =-min(0.5|P 1L +P 1R |,P ES,max ), P 2,ES =-min(0.5|P 2L +P 2R |,P ES,max );

[0031] Among them, C 1,k , C 2,k They are the negative sequence compensation factors of the first traction substation and the second traction substation respectively;

[0032] In the first half of regeneration condition:

[0033] Let P′ 1R =0;

[0034] As P 1L >0 and P 1L >|P 1R |, then let P′ 1L =P 1L -|P 1R |-P 1,ES , P 1,ES =-min(P 1L -|P 1R |,P ES,max );

[0035] As P 1L >0 and P 1L <|P 1R |, then let P′ 1L =0,P 1,ES =|P 1R |-|P 1L |;

[0036] As P 1L <0 and |P 1L |+|P1R |<P ES,max , then let P′ 1L =0,P 1,ES =|P 1L |+|P 1R |;

[0037] As P 1L <0 and |P 1L |+|P 1R |>P ES,max , then let P′ 1L =|P 1R |-|P 1L |,P 1,ES =P ES,max ;

[0038] P′ 2L =C 2,k (P 2L +P 2R +P 2,ES ), P′ 2R =(1-C 2,k )(P 2L +P 2R +P 2,ES ),

[0039] P 2,ES =-sgn(P 2L +P 2R )·min(0.5|P 2L +P 2R |,P ES,max );

[0040] Among them, sgn(x) is a function to judge whether it is positive or negative. If x is positive, it returns 1, and if it is negative, it returns -1.

[0041] In the second half regeneration condition:

[0042] Let P′ 2L =0;

[0043] As P 2R >0 and P 2R >|P 2L |, then let P′ 2R =P 2R -|P 2L |-P 2,ES , P 2,ES =-min(P 2R -|P 2L |,P ES,max );

[0044] As P 2R >0 and P 2R <|P2L |, then let P′ 2R =0,P 2,ES =|P 2L |-|P 2R |;

[0045] As P 2R <0 and |P 2L |+|P 2R |<P ES,max , then let P′ 2R =0,P 2,ES =|P 2R |+|P 2L |;

[0046] As P 2R <0 and |P 2L |+|P 2R |>P ES,max , then let P′ 2R =|P 2L |-|P 2R |,P 2,ES =P ES,max ;

[0047] P′ 1L =C 1,k (P 1L +P 1R +P 1,ES ), P′ 1R =(1-C 1,k )(P 1L +P 1R +P 1,ES ),

[0048] P 1,ES =-sgn(P 1L +P 1R )·min(0.5|P 1L +P 1R |,P ES,max );

[0049] Step 4: Calculate the output current reference value i on the left side of the first power flow control unit 1,rL , right side output current reference value i 1,rR , the output current reference value i on the left side of the second power flow control unit 2,rL , right side output current reference value i 2,rR ;

[0050] As P 1R <0, then

[0051]

[0052] As P2L <0, then

[0053]

[0054] Where P 1,rL is the output power reference value on the left side of the first power flow control unit, P 1,rR is the output power reference value on the right side of the first power flow control unit, P 2,rL is the output power reference value on the left side of the second power flow control unit, P 2,rR The reference value of the output power on the right side of the second power flow control unit:

[0055]

[0056] As P 1R >0, then

[0057]

[0058] As P 2L >0, then

[0059]

[0060] Where U 1L , U 1R , U 2L , U 2R Respectively represent the instantaneous voltage of the left and right power supply arms of the first traction substation and the second traction substation; I 1L ,I 1R ,I 2L ,I 2R Respectively represent the instantaneous current of the left and right power supply arms of the first traction substation and the second traction substation; N is the transformation ratio of the multi-winding transformer;

[0061] Step 5: According to i 1,rL ,i 1,rR ,i 2,rL ,i 2,rR , using the voltage and current double closed-loop control method, obtain the control signal of the back-to-back converter in the first power flow control unit and the second power flow control unit, and then control the back-to-back converter in the first power flow control unit and the second power flow control unit through PWM modulation; according to P 1,ES ,P 2,ES , using the voltage and current dual closed-loop control method, obtain the control signal of the bidirectional DC / DC converter in the first flow control unit and the second flow control unit, and then control the bidirectional DC / DC converter in the first flow control unit and the second flow control unit through PWM modulation.

[0062] The beneficial effects of the present invention are:

[0063] 1. A reverse power flow suppression and reuse system containing an energy storage system under the bilateral power supply topology of the traction power supply system is given.

[0064] 2. The upper-level energy management method can be used to achieve reasonable control of the current under different combinations of regeneration conditions and traction conditions of each power supply arm of the two stations, suppress the reverse current and reasonably use the regenerative braking energy; the negative-sequence reactive power management of the traction power supply system can also be achieved through current compensation control. BRIEF DESCRIPTION OF THE DRAWINGS

[0065] Figure 1 This is a schematic diagram of the structure of the power flow control system of the bilateral traction power supply station.

[0066] Figure 2 This is the structural diagram of the power flow control unit.

[0067] Figure 3 This is the control block diagram of the back-to-back converter in the power flow control unit. DETAILED DESCRIPTION

[0068] The specific embodiments of the present invention are described in detail below with reference to the accompanying drawings.

[0069] like Figure 1 , a bilateral traction power supply group power flow control system, the system is mainly composed of a multi-winding transformer, multiple back-to-back converters and a lithium battery energy storage part. In the figure, T is the contact wire and R is the rail.

[0070] The multiple back-to-back converters of each institute include: two groups of multiple cascaded four-quadrant converters connected to the left and right power supply arms of the traction network through a multi-winding step-down transformer, DC-side stabilizing capacitors and bidirectional DC converters connected to energy storage lithium batteries.

[0071] The power flow control system structures of the two traction substations are the same, and substation 1 is taken as an example for explanation.

[0072] Firstly, the AC / DC converter module of the back-to-back converter may adopt a structure such as an H-bridge cascade or an MMC (Modular Multilevel Converter).

[0073] like Figure 2 BTBC AC-DC converter topology adopts H-bridge cascade, which is easy to modularize and has good scalability, and is easy to access and manage the lithium battery energy storage part. Its output end is connected to the left and right power supply arms of the traction network through a multi-winding converter cascade, and the input end is connected in parallel through DC side capacitors to form a back-to-back structure.

[0074] The intermediate DC side voltage-stabilizing capacitor is connected to the bidirectional DC / DC converter. The required capacity of the energy storage lithium battery is determined according to the power level of the traction power supply system. Then, the series-parallel structure of the battery cells in the energy storage part is specifically determined according to the battery capacity and the DC side voltage limit to ensure reasonable control and stable operation of the energy storage part.

[0075] The control method of the bilateral traction power supply group power flow control system comprises the following steps:

[0076] Step 1: Collect the instantaneous voltage and current of the left and right power supply arms of the two traction transformers, and calculate the instantaneous power of the left and right power supply arms of substation 1 (referred to as substation 1) as P 1L , P 1R The instantaneous power of the left and right power supply arms of Substation 2 (abbreviated as Substation 2) are P 2L , P 2R ;

[0077] Step 2: According to P 1R and P 2L The load condition of the middle interconnected power supply arm is divided into three types: regeneration condition, semi-regeneration condition and full traction condition. When both middle power supply arms are in regeneration condition, that is, P 1R <0,P 2L <0, recorded as full regeneration condition; when one of the two intermediate interconnected power supply arms is in regeneration condition and the other is in traction condition, this includes two cases P 1R <0,P 2L >0, P 1R >0,P 2L <0, it is recorded as semi-regeneration condition; when the two middle power supply arms are both in traction condition, that is, P 1R >0,P 2L >0, it is recorded as full traction condition.

[0078] Step 3: Determine the active power distribution relationship between the two power supply arms based on the working conditions obtained in step 2, and obtain the active power distribution reference value P1' of the left and right power supply arms of the two power supply arms. L ,P1' R ,P2' L ,P2' R ,include:

[0079] 3.1 For semi-regeneration conditions, P 1R <0,P 2L >0, P 1R >0,P 2L <0 two situations.

[0080] ①P 1R <0,P 2L>0: For the right power supply arm 1, priority is given to ensuring that the regenerative braking energy is completely absorbed by the energy storage or transferred to the other power supply arm, i.e. P1' R =0, at this time, the active power distribution of the left power supply arm of station 1 needs to be determined according to the power situation of the left power supply arm of station 1, as shown in Table 1:

[0081] Table 1 Reference values ​​for power distribution

[0082]

[0083] For the left power supply arm of station 2, its BTBC can be considered to achieve power balance between the left and right power supply arms of the station to meet the negative sequence requirements. First, calculate the energy storage power reference value P 2,ES =-sgn(P 2L +P 2R )·min(0.5|P 2L +P 2R |,P ES,max );where sgn(x) is a function to judge whether it is positive or negative. If x is positive, it returns 1, and if it is negative, it returns -1. Usually, full compensation is not required. Here, a negative sequence compensation factor C is introduced. 2,k , determine C according to the requirements of negative sequence compensation 2,k When full compensation is required, C 2,k =0.5, then P2' L =P2' R =0.5(P 2L +P 2R +P 2,ES ). When full compensation is not required, C can be changed appropriately. 2,k The value can be taken in the range [0,1]. At this time, P2' L =C 2,k (P 2L +P 2R +P 2,ES ), P2' R =(1-C 2,k )(P 2L +P 2R +P 2,ES ).

[0084] ②P 1R >0,P 2L <0: For the left power supply arm 2, priority is given to ensuring that the regenerative braking energy is completely absorbed by the energy storage or transferred to the other power supply arm, i.e. P2' L =0, at this time, the active power distribution of the right power supply arm of station 2 needs to be determined according to the power situation of the left power supply arm of station 2, as shown in Table 2:

[0085] Table 2 Reference values ​​for power distribution

[0086]

[0087] For the right power supply arm of station 1, its BTBC can be considered to achieve power balance between the left and right power supply arms of the station. First, calculate the energy storage power reference value P 1,ES =-sgn(P 1L +P 1R )·min(0.5|P 1L +P 1R |,P ES,max ). When full compensation is required C 1,k =0.5, then P′ 1L =P′ 1R =0.5(P 1L +P 1R +P 1,ES ). When full compensation is not required, C can be changed appropriately. 1,k The value can be taken in the range [0,1]. At this time, P′ 1L =C 1,k (P 1L +P 1R +P 1,ES ), P′ 1R =(1-C 1,k )(P 1L +P 1R +P 1,ES ).

[0088] 3.2 For the full regeneration condition, the priority is to ensure that the regenerative braking energy of the two intermediate interconnected power supply arms is completely absorbed by the energy storage or transferred to the other power supply arm, that is, P′ 1R =0,P′ 2L =0, the power distribution of the left and right power supply arms of station 1 and station 2 is shown in Table 1 and Table 2.

[0089] 3.3 For full traction condition, that is, P 1R >0,P 2L >0, we do not need to consider the bypass return of the regenerative braking energy of the middle interconnected power supply arm, and we can consider the two stations separately to ensure that the power of the left and right power supply arms of the two stations is balanced. First, calculate the reference value of the energy storage power P of station 1 1,ES =min(0.5|P 1L +P 1R |,P ES,max ), the energy storage power reference value P 2,ES =min(0.5|P 2L +P 2R |,P ES,max ). At this time, negative sequence compensation factor C is also introduced into the two 1,k ,C 2,k , P′ 1L =C1,k (P 1L +P 1R +P 1,ES ), P′ 1R =(1-C 1,k )(P 1L +P 1R +P 1,ES ); P2' L =C 2,k (P 2L +P 2R +P 2,ES ), P2' R =(1-C 2,k )(P 2L +P 2R +P 2,ES ).

[0090] Step 4: For the interconnection side power supply arm in step 3, the power is negative (P 1R <0 or P 2L <0), the reference value of the output power of the BTBC port is obtained by subtracting the reference value of the power supply arm from the actual value, and then the effective value of the output current is calculated. Finally, the reference value of the output current of the corresponding port is obtained by combining the phase-locked loop locked phase information; for the power supply arm on the interconnection side in step 3, the power is positive (P 1R >0 or P 2L >0), calculate the instantaneous current value of the left and right power supply arms after reactive compensation and negative sequence compensation, and then make a difference with the actual current of the power supply arm to obtain the current reference value of each output port of BTBC. At the same time, the output current reference value in each case is finally multiplied by N (N is the transformation ratio of the multi-winding transformer), as follows:

[0091] 4.1 Calculate the power reference value P of each output port of BTBC 1,rL ,P 1,rR ,P 2,rL ,P 2,rR , :

[0092]

[0093] 4.2 Calculation of the reference value of the output port current of the traction substation BTBC with negative power supply arm on the interconnection side. Here, the subscript i is used to distinguish between substation 1 and substation 2 (i=1 for substation 1, i=2 for substation 2):

[0094]

[0095] 4.3 Calculation of the reference current value of the output port of the BTBC high-voltage side of the traction substation under power balance condition:

[0096] 4.3.1 Calculation of the instantaneous value of the current i′ at the converter output port after reactive power compensation and negative sequence compensation iL ,i′ iR ,

[0097]

[0098] 4.3.2 Calculate the current reference values ​​of the left and right output ports on the high voltage side of the BTBC multi-winding transformer.

[0099]

[0100] Step 5: Based on the current reference value i of each BTBC output port obtained in step 4 1,rL ,i 1,rR ,i 2,rL ,i 2,rR , which can realize the utilization of regenerative braking energy of bilateral power supply system and the corresponding negative sequence reactive power compensation function. At the same time, in order to realize the normal access of energy storage device in BTBC, the actual DC voltage U dc and reference value The voltage is stabilized by differential PI control. The modulation signals of the left and right converters of the two BTBCs are obtained through the voltage outer loop and current inner loop double loop control. At the same time, the modulation signal of the energy storage device converter is obtained through the current inner loop according to the quotient of the energy storage power reference value and the DC side voltage.

[0101] 5.1 The converter port current reference value i obtained in step 4 is 1,rL ,i 1,rR ,i 2,rL ,i 2,rR and the actual value i 1L ,i 1R ,i 2L ,i 2R The difference is passed into the current inner loop for PI control, and then multiplied by the voltage synchronization phase information of the left and right arms locked by PLL to obtain the active current control component of the DC voltage control on the left and right sides of BTBC, so as to achieve DC side voltage stability;

[0102] 5.2 The active current components controlled by the DC voltage on the left and right sides of the BTBC in 5.1 are superimposed on the power balance compensation current respectively, and then the difference PI regulation control is performed with the actual output current of the BTBC respectively, and finally the modulation signal for actually controlling each converter of the BTBC is obtained.

[0103] 5.3 Based on the power reference values ​​P of the two energy storage devices obtained in step 3 1,ES ,P 2,ESThe reference value of the energy storage device port current is obtained by dividing the current by the DC side voltage Then, the converter modulation signal of each energy storage device is obtained through the current inner loop control.

[0104] Step 6: The modulation signal obtained in step 5 is modulated by PWM to send out a switching signal for controlling the BTBC and the energy storage system, so as to realize the accurate coordinated operation of the actual system under the energy management strategy and complete the power flow control under various working conditions.

[0105] The present invention realizes reasonable control of the current under different combinations of regeneration conditions and traction conditions of each power supply arm of the two stations through the upper-level energy management strategy, completes the suppression of reverse current and the reasonable use of regenerative braking energy; and realizes negative-sequence reactive power management of the traction power supply system through BTBC current compensation control.

Claims

1. A bilateral traction power supply group power flow control system, the bilateral traction power supply group comprises a first traction substation and a second traction substation; the secondary side of the V / v traction transformer of the first traction substation is respectively connected to the left and right power supply arms of the first traction substation, the secondary side of the V / v traction transformer of the second traction substation is respectively connected to the left and right power supply arms of the second traction substation; the right power supply arm of the first traction substation is interconnected with the left power supply arm of the second traction substation; It is characterized in that It includes a first power flow control unit; the first power flow control unit includes a left multi-winding transformer, a right multi-winding transformer, a bidirectional DC / DC converter and an energy storage device, and also includes a plurality of back-to-back converters; the primary side of the left multi-winding transformer is connected to the left power supply arm of the first traction substation, and the primary side of the right multi-winding transformer is connected to the right power supply arm of the first traction substation; Each secondary side of the left multi-winding transformer is respectively connected to the left output end of a back-to-back converter, and each secondary side of the right multi-winding transformer is respectively connected to the right output end of a back-to-back converter; after the input ends of all back-to-back converters are connected in parallel, they are connected to the energy storage device through a bidirectional DC / DC converter; a voltage stabilizing capacitor is also provided at the input end of the back-to-back converter; Also includes a second power flow control unit with the same structure as the first power flow control unit; The primary side of the left multi-winding transformer of the second power flow control unit is connected to the left power supply arm of the second traction substation, and the primary side of the right multi-winding transformer is connected to the right power supply arm of the second traction substation.

2. A bilateral traction power supply group power flow control system as claimed in claim 1, It is characterized in that The AC / DC converter module of the back-to-back converter adopts H-bridge cascade or MMC cascade.

3. The control method of the bilateral traction power supply group power flow control system according to claim 1, It is characterized in that include: Step 1: Collect the instantaneous voltage and current of the left and right power supply arms of the first traction substation and the second traction substation, and calculate the instantaneous power P of the left and right power supply arms of the first traction substation and the second traction substation. 1L , P 1R , P 2L , P 2R ; Step 2, determine the current working conditions: As P 1R <0 and P 2L <0, it is full regeneration condition; As P 1R >0 and P 2L >0, it is full traction condition; As P 1R <0 and P 2L >0, it is the first half regeneration condition; As P 1R >0 and P 2L <0, it is the second half regeneration condition; Step 3: According to the current working conditions, the active power of the left and right power supply arms of the first traction substation and the second traction substation is allocated to obtain the active power allocation reference value P 1 ' L , P 1 ' R , P 2 ' L , P 2 ' R , and the energy storage device power reference value P of the first power flow control unit and the second power flow control unit 1,ES ,P 2,ES ; Under full regeneration conditions: Let P 1 ' R =0; As P 1L >0 and P 1L >|P 1R |, then let P 1 ' L =P 1L -|P 1R |-P 1,ES , P 1,ES =-min(P 1L -|P 1R |,P ES,max ); As P 1L >0 and P 1L <|P 1R |, then let P' 1L =0,P 1,ES =|P 1R |-|P 1L |; As P 1L <0 and |P 1L |+|P 1R |<P ES,max , then let P' 1L =0,P 1,ES =|P 1L |+|P 1R |; As P 1L <0 and |P 1L |+|P 1R |>P ES,max , then let P' 1L =|P 1R |-|P 1L |,P 1,ES =P ES,max ; Let P' 2L =0; As P 2R >0 and P 2R >|P 2L |, then let P' 2R =P 2R -|P 2L |-P 2,ES , P 2,ES =-min(P 2R -|P 2L |,P ES,max ); As P 2R >0 and P 2R <|P 2L |, then let P' 2R =0,P 2,ES =|P 2L |-|P 2R |; As P 2R <0 and |P 2L |+|P 2R |<P ES,max , then let P' 2R =0,P 2,ES =|P 2R |+|P 2L |; As P 2R <0 and |P 2L |+|P 2R |>P ES,max , then let P' 2R =|P 2L |-|P 2R |,P 2,ES =P ES,max ; Among them, P ES,max The maximum output power of the energy storage device of the first power flow control unit and the second power flow control unit; Under full traction conditions: P’ 1L =C 1,k (P 1L +P 1R +P 1,ES ),P’ 1R =(1-C 1,k )(P 1L +P 1R +P 1,ES ); P’ 2L =C 2,k (P 2L +P 2R +P 2,ES ),P’ 2R =(1-C 2,k )(P 2L +P 2R +P 2,ES ); P 1,ES =-min(0.5|P 1L +P 1R |,P ES,max ),P 2,ES =-min(0.5|P 2L +P 2R |,P ES,max ); Among them, C 1,k , C 2,k They are the negative sequence compensation factors of the first traction substation and the second traction substation respectively; In the first half of regeneration condition: Let P 1 ' R =0; As P 1L >0 and P 1L >|P 1R |, then let P' 1L =P 1L -|P 1R |-P 1,ES , P 1,ES =-min(P 1L -|P 1R |,P ES,max ); As P 1L >0 and P 1L <|P 1R |, then let P' 1L =0,P 1,ES =|P 1R |-|P 1L |; As P 1L <0 and |P 1L |+|P 1R |<P ES,max , then let P' 1L =0,P 1,ES =|P 1L |+|P 1R |; As P 1L <0 and |P 1L |+|P 1R |>P ES,max , then let P 1 ' L =|P 1R |-|P 1L |,P 1,ES =P ES,max ; P’ 2L =C 2,k (P 2L +P 2R +P 2,ES ),P’ 2R =(1-C 2,k )(P 2L +P 2R +P 2,ES ), P 2,ES =-sgn(P 2L +P 2R )·min(0.5|P 2L +P 2R |,P ES,max ); Among them, sgn(x) is a function to judge whether it is positive or negative. If x is positive, it returns 1, and if it is negative, it returns -1. In the second half regeneration condition: Let P' 2L =0; As P 2R >0 and P 2R >|P 2L |, then let P' 2R =P 2R -|P 2L |-P 2,ES , P 2,ES =-min(P 2R -|P 2L |,P ES,max ); As P 2R >0 and P 2R <|P 2L |, then let P' 2R =0,P 2,ES =|P 2L |-|P 2R |; As P 2R <0 and |P 2L |+|P 2R |<P ES,max , then let P' 2R =0,P 2,ES =|P 2R |+|P 2L |; As P 2R <0 and |P 2L |+|P 2R |>P ES,max , then let P' 2R =|P 2L |-|P 2R |,P 2,ES =P ES,max ; P’ 1L =C 1,k (P 1L +P 1R +P 1,ES ),P’ 1R =(1-C 1,k )(P 1L +P 1R +P 1,ES ), P 1,ES =-sgn(P 1L +P 1R )·min(0.5|P 1L +P 1R |,P ES,max ); Step 4: Calculate the output current reference value i on the left side of the first power flow control unit 1,rL , right side output current reference value i 1,rR , the output current reference value i on the left side of the second power flow control unit 2,rL , right side output current reference value i 2,rR ; As P 1R <0, then As P 2L <0, then Where P 1,rL is the output power reference value on the left side of the first power flow control unit, P 1,rR is the output power reference value on the right side of the first power flow control unit, P 2,rL is the output power reference value on the left side of the second power flow control unit, P 2,rR The reference value of the output power on the right side of the second power flow control unit: As P 1R >0, then As P 2L >0, then Where U 1L , U 1R , U 2L , U 2R Respectively represent the instantaneous voltage of the left and right power supply arms of the first traction substation and the second traction substation; I 1L ,I 1R ,I 2L ,I 2R Respectively represent the instantaneous current of the left and right power supply arms of the first traction substation and the second traction substation; N is the transformation ratio of the multi-winding transformer; Step 5: According to i 1,rL ,i 1,rR ,i 2,rL ,i 2,rR , using the voltage and current double closed-loop control method, obtain the control signal of the back-to-back converter in the first power flow control unit and the second power flow control unit, and then control the back-to-back converter in the first power flow control unit and the second power flow control unit through PWM modulation; according to P 1,ES ,P 2,ES , using the voltage and current dual closed-loop control method, obtain the control signal of the bidirectional DC / DC converter in the first power flow control unit and the second power flow control unit, and then control the bidirectional DC / DC converter in the first power flow control unit and the second power flow control unit through PWM modulation.

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