Bidirectional converter traction power supply system, control method and readable storage medium

Abstract

The present application discloses a bidirectional converter traction power supply system, control method, and readable storage medium, belonging to the field of rail transit technology. The power supply system includes N traction substations, a main substation, and a control center. The traction substation is equipped with two bidirectional converters, which are respectively connected to the traction substation section I and section II busbars. The main substation includes the main substation section I and section II busbars. The control center is located in the main substation, and a communication connection is established between the control center and the bidirectional converter. The control center is configured to adjust the control mode of the bidirectional converters in each traction substation; monitor the load of the main substation section I and section II busbars based on the control mode to adjust the power ratio of the bidirectional converters in each traction substation according to the load balance; and de-ice the contact lines of adjacent traction substations based on the control mode switching. This application aims to solve the technical problems of load imbalance, active power reverse transmission, and contact line icing in the main substation.

Description

Technical Field

[0001] The present application belongs to the field of rail transit technology, and specifically relates to a bidirectional converter traction power supply system, a control method and a readable storage medium. Background Art

[0002] The traditional traction power supply system uses an uncontrolled rectifier unit and a subway regenerative power feedback device. Two 12-pulse rectifier units in a traction substation are connected to the same busbar section to form a 24-pulse uncontrolled rectifier unit. Adjacent traction substations in the same section have 24-pulse uncontrolled rectifier units and regenerative power processing devices connected alternately to the Section I / Section II busbars of the medium-voltage power supply network. During normal operation, the Section I / Section II bus tie breaker is disconnected. The existing power supply system and operating methods present the following problems:

[0003] (1) During peak hours in the morning and evening, multiple trains are running on the line, and train traction and braking are frequent. This causes multiple stations with the same busbar rectifier units or subway regenerative power feedback devices to operate simultaneously, resulting in load imbalance between Section I and Section II of the main substation and active power reverse transmission problems.

[0004] (2) For traction substations with access to renewable energy power generation such as photovoltaic and wind power, the renewable energy power generation power is fed back to a certain section of the busbar through the subway regenerative power feedback device. Considering the intermittent and random nature of the operating power, there are also problems of load imbalance and active power reverse transmission;

[0005] (3) When the subway regenerative power processing device of the adjacent traction substation is performing catenary de-icing at night, on the one hand, a switching operation is required to disconnect the electrical connection between the catenary in the de-icing section and other catenary to avoid circulation of current between the de-icing station equipment and other station equipment; on the other hand, since the subway regenerative power processing device is connected to different sections of the busbar, the circulating power is relatively large during the de-icing process. Since the main substation load is relatively low at night, active power reverse transmission is likely to occur, resulting in a large de-icing electricity charge. Summary of the Invention

[0006] Purpose of the invention: This application develops a bidirectional converter traction power supply system, a control method and a readable storage medium, aiming to solve the technical problems of load imbalance, active power reverse transmission and contact network icing in the existing technology in the main substation.

[0007] Technical Solution: In a first aspect, an embodiment of the present application provides a bidirectional converter traction power supply system, comprising:

[0008] N traction substations, each of which is provided with two sets of bidirectional converters, the two sets of bidirectional converters being respectively connected to the corresponding AC medium-voltage power supply network traction substation section I busbar and traction substation section II busbar, the two sets of bidirectional converters in each traction substation being connected by communication, the control modes of the bidirectional converters including voltage control mode and power control mode, N is a positive integer, N ≥ 2;

[0009] Main substation, comprising main substation section I busbar and main substation section II busbar;

[0010] A control center, the control center being located in the main substation and being communicatively connected to each of the bidirectional converters;

[0011] The control center is configured to adjust the control mode of the bidirectional converter in each of the traction substations; and, based on the control mode, monitor the load of the bus section I and the bus section II of the main substation, so as to adjust the power ratio of the two sets of bidirectional converters in each of the traction substations according to the load balance situation, and based on the control mode switching, achieve ice melting of the contact networks of adjacent traction substations without the need for switching operations.

[0012] In some embodiments, in the two sets of bidirectional converters in the traction substation:

[0013] One set of the bidirectional converters operates based on the voltage control mode, and the other set of the bidirectional converters operates based on the power control mode;

[0014] The operating states of the bidirectional converter based on the voltage control mode include a first traction rectification state, a first energy feedback state, and a no-load voltage stabilization state;

[0015] The operating states of the bidirectional converter operating in the power control mode include a second traction rectification state, a second energy feedback state, and a locked standby state.

[0016] In some embodiments, the bidirectional converter operates based on the voltage control mode, including:

[0017] The bidirectional converter monitors the DC side voltage U in real time dc ;

[0018] When the DC side voltage U dc Greater than the threshold voltage U for starting the first energy feedback state set1 When , the bidirectional converter enters the first energy feedback state and controls the DC side voltage to be constant.

[0019] In some embodiments, the bidirectional converter operates based on the power control mode, including:

[0020] The bidirectional converter operating in the power control mode obtains the real-time operating power P1 of the bidirectional converter operating in the voltage control mode;

[0021] When the real-time operating power P1 is less than the threshold power P for starting the second energy feedback state set1 When the bidirectional converter operates based on the power control mode, it enters the second energy feedback state and performs constant power control according to the first power control instruction P_hk. The first power control instruction P_hk is determined based on the load balancing coefficient K1 of the two sets of bidirectional converters in the energy feedback state, the real-time operating power P1 and the operating power of the bidirectional converter operating based on the power control mode.

[0022] In some embodiments, the bidirectional converter operates based on the power control mode and further includes:

[0023] When the real-time operating power P1 is greater than the threshold power P1 for starting the second traction rectification state set2 When the bidirectional converter operates based on the power control mode, it enters the second traction rectification state and performs constant power control according to the second power control instruction P_qy. The second power control instruction P_qy is determined based on the load balancing coefficient K2 of the two sets of bidirectional converters in the traction rectification state, the real-time operating power P1 and the operating power of the bidirectional converter operating based on the power control mode.

[0024] In some embodiments, the power supply system further comprises a power flow control unit configured to monitor the bus load P of section I of the main substation in real time. z1 and the busbar load P of section II of the main substation z2 , the control center is connected to the power flow control unit and is further configured to perform the following steps:

[0025] When the busbar load P of section I of the main substation z1 Less than the active reverse power criterion P of busbar section I of main substation zset1 When , it is determined that the active power reverse transmission phenomenon occurs on the busbar of section I of the main substation;

[0026] When the busbar load P of the main substation II section z2 Less than the active reverse power criterion P of the busbar of section I of the main substation zset1 When the active power reverse transmission phenomenon occurs on the busbar of section II of the main substation;

[0027] When |P z1 -P z2 |<P zset2 When P zset2The load imbalance criterion for the busbars of the main substation section I and the main substation section II is to determine that the loads of the busbars of the main substation section I and the busbars of the main substation section II are unbalanced.

[0028] In some embodiments, the control center is further configured to perform the following steps:

[0029] identifying the operating status of all the bidirectional converters;

[0030] For the traction substation where the bidirectional converter in the first traction rectification state or the second traction rectification state is located, the load balancing coefficient K2 of the two bidirectional converters in the traction rectification state is adjusted according to the connection relationship between the bidirectional converter operating based on the power control mode and the traction substation section I bus and the traction substation section II bus, combined with the active power reverse transmission phenomenon determination result of the main substation section I bus and the main substation section II bus or the load balance determination result of the main substation section I bus and the main substation section II bus;

[0031] For the traction substation where the bidirectional converter is located in the first energy feedback state or the second energy feedback state, the load balancing coefficient K1 of the two sets of bidirectional converters in the energy feedback state is adjusted according to the connection relationship between the bidirectional converter operating based on the power control mode and the traction substation section I bus and the traction substation section II bus, combined with the active power reverse transmission phenomenon judgment result of the main substation section I bus and the main substation section II bus or the load balance judgment result of the main substation section I bus and the main substation section II bus.

[0032] In some embodiments, the power supply system further includes an ice melting control unit. The control center is configured to determine a catenary ice melting section and ice melting duration, and to determine that the traction substations at both ends of the section are traction substation X and traction substation Y, respectively. The control center is connected to the ice melting control unit, and the ice melting control unit is configured to perform the following steps:

[0033] controlling the X traction substation to operate in the voltage control mode;

[0034] controlling the traction substations other than the X traction substation to operate in the power control mode;

[0035] The de-icing power of the two sets of bidirectional converters in the Y traction substation is controlled, and both are locked when a predetermined de-icing time is reached.

[0036] In some embodiments, when a bidirectional converter operating in the voltage control mode fails or an AC bus to which it is connected fails, the bidirectional converter operating in the voltage control mode is configured to exit operation, and the bidirectional converter operating in the power control mode is configured to continue operating in the voltage control mode.

[0037] When the bidirectional converter operating based on the power control mode fails or the AC bus to which it is connected fails, the bidirectional converter operating based on the power control mode is configured to exit operation, and the bidirectional converter operating based on the voltage control mode is configured to continue operating according to the power control mode.

[0038] In a second aspect, an embodiment of the present application provides a control method for a traction power supply system according to any one of the first aspects, the control method comprising:

[0039] The control center adjusts the control mode of the bidirectional converters in each traction substation;

[0040] Based on the control mode, the control center monitors the load of the busbar section I and the busbar section II of the main substation to adjust the power ratio of the two sets of bidirectional converters in each traction substation according to the load balance situation, and melts the ice of the contact network of adjacent traction substations based on the control mode switching.

[0041] In some embodiments, one set of the bidirectional converters in the traction substation operates based on the voltage control mode, and another set of the bidirectional converters in the traction substation operates based on the power control mode. The control method further includes:

[0042] The bidirectional converter operating in the voltage control mode monitors the DC side voltage U in real time. dc ;

[0043] If the DC side voltage U dc Greater than the threshold voltage U for starting the first energy feedback state set1 , the bidirectional converter operating based on the voltage control mode enters the first energy feedback state and controls the DC side voltage to be constant.

[0044] In some embodiments, the control method further includes: the bidirectional converter operating in the power control mode acquires a real-time operating power P1 of the bidirectional converter operating in the voltage control mode;

[0045] If the real-time operating power P1 is less than the threshold power P for starting the second energy feedback state, set1 , the bidirectional converter operating based on the power control mode enters the second energy feedback state and performs constant power control according to the first power control instruction P_hk;

[0046] If the real-time operating power P1 is greater than the threshold power P1 for starting the second traction rectification state set2 , the bidirectional converter operating based on the power control mode enters the second traction rectification state and performs constant power control according to the second power control instruction P_qy.

[0047] According to a third aspect, a readable storage medium is provided, on which a computer program is stored. When the computer program is executed by a processor, the control method is implemented.

[0048] Beneficial effects:

[0049] 1. In this application, the operating power ratio between the two sets of bidirectional converters in the traction substation is adjustable, which effectively solves the problems of unbalanced load and active power reverse transmission in the main substation. This power supply system is suitable for subway lines where all trains have eliminated on-board resistors. Compared with the method of adjusting the starting threshold of adjacent stations, it reduces the overhead contact line loss and eliminates the problem of overhead contact voltage fluctuation.

[0050] 2. The control modes of the bidirectional converter in the present application include a voltage control mode and a power control mode; when the bidirectional converter operating in the voltage control mode in the traction substation fails or the AC bus to which it is connected fails, the bidirectional converter operating in the voltage control mode exits operation, and the other bidirectional converter operating in the power control mode continues to operate in accordance with the voltage control mode; when the bidirectional converter operating in the power control mode in the traction substation fails or the AC bus to which it is connected fails, the bidirectional converter operating in the power control mode exits operation, and the other bidirectional converter operating in the voltage control mode continues to operate in accordance with the power control mode, thereby improving the operational reliability of the power supply system.

[0051] 3. This application controls the operation mode of the bidirectional converter, without the need for switching operations, to achieve ice melting of the contact network of adjacent traction substations and reduce ice melting losses.

[0052] 4. In this application, the bidirectional converter in the power control mode of the traction substation is in a locked state when there is no train braking. On the one hand, it reduces the operating loss, and on the other hand, it avoids the circulation between the bidirectional converters within the station and between stations, effectively reducing the circulation loss. BRIEF DESCRIPTION OF THE DRAWINGS

[0053] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present application. For those skilled in the art, other drawings can be obtained based on these drawings without creative work.

[0054] Figure 1A schematic structural diagram of a bidirectional converter traction power supply system provided in an embodiment of the present application;

[0055] Figure 2 This is a control flow diagram of the bidirectional converter in the voltage control mode according to an embodiment of the present application;

[0056] Figure 3 This is a control flow diagram of the bidirectional converter in the power control mode according to an embodiment of the present application;

[0057] Figure 4 This is a control flow diagram of the power flow control unit in an embodiment of the present application;

[0058] Figure 5 This is a control flow chart of the ice melting control unit in the embodiment of the present application.

[0059] Figure 1: 1st main substation transformer; 2nd main substation transformer; 3. Control center; 4. No. 1_1 bidirectional converter; 5. No. 1_2 bidirectional converter; 6. No. 2_1 bidirectional converter; 7. No. 2_2 bidirectional converter; 8. No. N_1 bidirectional converter; 9. No. N_2 bidirectional converter; 10. 110kV busbar of section I of the first main substation; 11. 110kV busbar of the first main substation; 12. 110kV busbar of section II of the second main substation; 13. Main substation; 14. 35kV busbar of section I of the first traction substation; 15. 35kV busbar of the first traction substation; 16. 35kV busbar of section II of the first traction substation; 17. 35kV busbar of section I of the second traction substation; 18. 35kV busbar of the second traction substation; 19. 35kV busbar of the second traction substation Section II busbar; 20. 35kV Section I busbar of the Nth traction substation; 21. 35kV bus tie switch of the Nth traction substation; 22. 35kV Section II busbar of the Nth traction substation; 23. First traction substation; 24. Second traction substation; 25. Nth traction substation; 26. DC overhead line; 27. Rails. DETAILED DESCRIPTION

[0060] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the embodiments described are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without making creative efforts are within the scope of protection of this application.

[0061] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "connected" and "connected" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection, an electrical connection, or mutual communication; it can be directly connected, or indirectly connected through an intermediate medium, or it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to the specific circumstances. In the description of the present invention, the meaning of "multiple" is two or more, unless otherwise clearly specified and specifically limited. In addition, the terms "first" and "second" are used for descriptive purposes only, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more features.

[0062] The disclosure below provides many different embodiments or examples to realize different structures of the present invention. In order to simplify the disclosure of the present invention, the parts and settings of specific examples are described below. Of course, they are only examples, and the purpose is not to limit the present invention.

[0063] See also Figures 1 to 5 As shown, embodiments of the present application provide a bidirectional converter traction power supply system, which belongs to the field of rail transit technology and is suitable for power flow control and automatic ice melting in bidirectional converter traction power supply systems for rail transit. The bidirectional converter traction power supply system of the present application includes: a main substation 13, N traction substations, and a control center 3.

[0064] In the embodiment of the present application, the main substation 13 includes a main substation section I busbar and a main substation section II busbar; specifically, Figure 1 As shown, the main substation section I busbar and the main substation section II busbar are respectively the first main substation section I 110kV busbar 10 and the second main substation section II 110kV busbar 12.

[0065] In some embodiments, the main substation 13 further includes a first main substation transformer 1 and a second main substation transformer 2. Specifically, the first main substation transformer 1 is connected to the 110kV busbar 10 of Section I of the first main substation, and the second main substation transformer 2 is connected to the 110kV busbar 12 of Section II of the second main substation. A first main substation 110kV bus tie switch 11 is provided between the 110kV busbar 10 of Section I of the first main substation and the 110kV busbar 12 of Section II of the second main substation.

[0066] In an embodiment of the present application, two sets of bidirectional converters are provided in each traction substation, and the two sets of bidirectional converters are respectively connected to the corresponding AC medium-voltage power supply network traction substation section I bus and traction substation section II bus, and communication connection is adopted between the two sets of bidirectional converters in each traction substation.

[0067] In some embodiments, the number of traction substations is N, where N is a positive integer and N≥2.

[0068] It needs to be further explained that, Figure 1As shown, the N traction substations are arranged in sequence as the first traction substation 23, the second traction substation 24, ..., the Nth traction substation 25. The two sets of bidirectional converters in the first traction substation 23 are bidirectional converter No. 1_1 4 and bidirectional converter No. 1_2 5, respectively. The two sets of bidirectional converters in the second traction substation 24 are bidirectional converter No. 2_1 6 and bidirectional converter No. 2_2 7, respectively. The two sets of bidirectional converters in the Nth traction substation 25 are bidirectional converter No. N_1 8 and bidirectional converter No. N_2 9. Bidirectional converter No. 1_1 4 is connected to the 35kV I section bus 14 of the first traction substation, which is connected to the transformer 1 of the first main substation; bidirectional converter No. 1_2 5 is connected to the 35kV II section bus 16 of the first traction substation, which is connected to the transformer 2 of the second main substation; the 35kV II section bus 16 of the first traction substation is connected to the transformer 2 of the second main substation; A first traction substation 35kV bus tie switch 15 is provided between the I section bus 14 and the first traction substation 35kV II section bus 16. The 2_1 bidirectional converter 6 is connected to the second traction substation 35kV I section bus 17, and the second traction substation 35kV I section bus 17 is connected to the first traction substation 35kV I section bus 14; the 2_2 bidirectional converter 7 is connected to the second traction substation 35kV II section bus 19, and the second traction substation 35kV II section bus 19 is connected to the first traction substation 35kV II section bus 16; a second traction substation 35kV bus tie switch 18 is provided between the second traction substation 35kV I section bus 17 and the second traction substation 35kV II section bus 19. Bidirectional converter No. N_1 is connected to the 35kV busbar I section 20 of the Nth traction substation, which is in turn connected to the 35kV busbar I section of the N-1th traction substation. Bidirectional converter No. N_2 is connected to the 35kV busbar II section 22 of the Nth traction substation, which is in turn connected to the 35kV busbar II section of the N-1th traction substation. A 35kV bus tie switch 21 is installed between the 35kV busbar I section 20 and the 35kV busbar II section 22 of the Nth traction substation. The positive and negative poles of each bidirectional converter are connected to the DC overhead line 26 and rails 27, respectively.

[0069] In some embodiments, the control modes of the bidirectional converter include a voltage control mode and a power control mode. The voltage control mode is a power system operation mode designed to maintain the voltage level at a specific node in the power system. The power control mode is a power system control mode in which power is the primary regulation variable in the system.

[0070] It should be further explained that the operating states of a bidirectional converter operating in voltage control mode include a first traction rectification state, a first energy regeneration state, and a no-load voltage regulation state; while the operating states of a bidirectional converter operating in power control mode include a second traction rectification state, a second energy regeneration state, and a locked standby state. The first traction rectification state is identical to the second traction rectification state, and the first energy regeneration state is identical to the second energy regeneration state.

[0071] In an embodiment of the present application, a traction substation includes two bidirectional converters, one of which operates in a voltage-controlled mode and the other in a power-controlled mode. Specifically, if the two bidirectional converters in the traction substation are defined as bidirectional converter a and bidirectional converter b, then either: bidirectional converter a operates in a voltage-controlled mode and bidirectional converter b operates in a power-controlled mode; or bidirectional converter a operates in a power-controlled mode and bidirectional converter b operates in a voltage-controlled mode.

[0072] In the prior art, when the AC bus corresponding to the rectifier unit fails, the traction substation completely loses its traction power supply capability, and the system operation reliability is low. In the present application, when the bidirectional converter operating based on the voltage control mode fails or the AC bus to which it is connected fails, the bidirectional converter operating based on the voltage control mode is configured to exit operation, and the bidirectional converter operating based on the power control mode is configured to continue operating according to the voltage control mode; when the bidirectional converter operating based on the power control mode fails or the AC bus to which it is connected fails, the bidirectional converter operating based on the power control mode is configured to exit operation, and the bidirectional converter operating based on the voltage control mode is configured to continue operating according to the power control mode. That is, when a section of the AC bus fails, the bidirectional converter corresponding to another section of the AC bus can still operate normally, thereby improving the operational reliability of the bidirectional converter traction power supply system.

[0073] In some embodiments, as Figure 2 As shown, the bidirectional converter operates based on the voltage control mode, and the bidirectional converter monitors the DC side voltage U in real time. dc ; when U dc >U set1 When U set1 is the threshold voltage for starting the first energy feedback state.

[0074] In some embodiments, as Figure 2 As shown, the bidirectional converter operates based on the voltage control mode, and the bidirectional converter monitors the DC side voltage U in real time. dc ; when U set2 ≤U dc ≤U set1When the bidirectional converter enters the first no-load voltage regulation state, the droop control is performed according to the first droop coefficient Z1. set2 It is the threshold voltage for starting the first traction rectification state.

[0075] In some embodiments, as Figure 2 As shown, the bidirectional converter operates based on the voltage control mode, and the bidirectional converter monitors the DC side voltage U in real time. dc ; when U dc <U set2 When , the bidirectional converter enters the first traction rectification state and performs droop control according to the second droop coefficient Z2.

[0076] It should be further explained that the first droop coefficient Z1 and the second droop coefficient Z2 satisfy: |Z2|<|Z1|.

[0077] In some embodiments, the bidirectional converter operates based on the power control mode, and the bidirectional converter operating in the power control mode obtains the real-time operating power P1 of the bidirectional converter operating in the voltage control mode; when P set1 ≤P1≤P set2 When the bidirectional converter in power control mode enters the locked standby state, P set1 The threshold power for starting the second energy feedback state, P set2 The threshold power for starting the second traction rectification state.

[0078] In some embodiments, the bidirectional converter operates based on the power control mode, and the bidirectional converter operating in the power control mode obtains the real-time operating power P1 of the bidirectional converter operating in the voltage control mode; when P1 < P set1 When , the bidirectional converter operating in the power control mode enters the second energy feedback state and performs constant power control according to the first power control instruction P_hk.

[0079] It should be further explained that P_hk=K1*(P1+P2), K1 is the load balancing coefficient of the two bidirectional converters in the energy feedback state, P2 is the operating power of the bidirectional converter based on the power control mode, and 0≤K1≤1.

[0080] In some embodiments, the bidirectional converter operates based on the power control mode, and the bidirectional converter operating in the power control mode obtains the real-time operating power P1 of the bidirectional converter operating in the voltage control mode; when P1>P set2 When , the bidirectional converter operating in the power control mode enters the second traction rectification state and performs constant power control according to the second power control instruction P_qy.

[0081] It should be further explained that P_qy=K2*(P1+P2), K2 is the load balancing coefficient of the two sets of bidirectional converters in the traction rectification state, and 0≤K2≤1.

[0082] In an embodiment of the present application, the control center 3 is located in the main substation 13, and a communication connection is adopted between the control center 3 and each bidirectional converter; the control center 3 is configured to adjust the control mode of the bidirectional converter in each traction substation, and monitor the load of the main substation section I bus and the main substation section II bus based on the control mode, so as to adjust the power ratio of the bidirectional conversion of the bidirectional converter in each traction substation according to the load balance situation, and based on the control mode switching, without the need for switching operations, to achieve ice melting of the contact network of adjacent traction substations.

[0083] In the embodiment of the present application, the power supply system further includes a flow control unit, which is configured to monitor the bus load P of the main substation I section in real time. z1 and the busbar load P of section II of the main substation z2 , the control center 3 is connected to the flow control unit.

[0084] In some embodiments, as Figure 3 As shown, the power flow control unit is further configured to perform the following steps:

[0085] When the busbar load P of section I of the main substation is z1 Less than the active reverse power criterion P of busbar section I of main substation zset1 When the power is reversed, it is determined that the busbar of section I of the main substation has active power reverse transmission;

[0086] When the busbar load P of section II of the main substation is z2 Less than the active reverse power criterion P of busbar section I of main substation zset1 When the main substation II busbar is detected, active power reverse transmission occurs;

[0087] When |P z1 -P z2 |<P zset2 When P zset2 The load imbalance criterion for the busbars of section I and section II of the main substation is used to determine whether the load of the busbars of section I and section II of the main substation is unbalanced.

[0088] In some embodiments, as Figure 4 As shown, the control center 3 is further configured to perform the following steps:

[0089] Identify the operating status of all bidirectional converters;

[0090] For the traction substation where the bidirectional converter in the first traction rectification state or the second traction rectification state is located, the load balancing coefficient K2 of the two bidirectional converters in the traction rectification state is adjusted according to the connection relationship between the bidirectional converter operating in the power control mode and the traction substation section I busbar and the traction substation section II busbar, combined with the active power reverse transmission phenomenon judgment result of the main substation section I busbar and the main substation section II busbar, or the load balance judgment result of the main substation section I busbar and the main substation section II busbar;

[0091] For the traction substation where the bidirectional converter is in the first energy feedback state or the second energy feedback state, the load balancing coefficient K1 of the two sets of bidirectional converters in the energy feedback state is adjusted according to the connection relationship between the bidirectional converter operating based on the power control mode and the traction substation section I bus and the traction substation section II bus, combined with the active power reverse transmission phenomenon judgment result of the main substation section I bus and the main substation section II bus or the load balance judgment result of the main substation section I bus and the main substation section II bus.

[0092] In some embodiments, after determining that active power reverse transmission occurs on the busbar section I of the main substation, the control center 3 is configured to adjust K2 and K1 through the following steps:

[0093] Identify the operating status of all bidirectional converters, number the traction substations where the bidirectional converters operating in the first traction rectification state or the second traction rectification state are located into a first group, and number the traction substations where the bidirectional converters operating in the first energy feedback state or the second energy feedback state are located into a second group;

[0094] For the traction substations in the first group, if the bidirectional converter operating in power control mode is connected to the busbar section I of the traction substation, K2 is increased; if it is connected to the busbar section II of the traction substation, K2 is decreased.

[0095] For the traction substation in the second group, if the bidirectional converter operating in power control mode is connected to the traction substation section I bus, K1 is reduced; if it is connected to the traction substation section II bus, K1 is increased.

[0096] In some embodiments, after active power reverse occurs on the busbar section II of the main substation, the control center 3 is configured to adjust K2 and K1 through the following steps:

[0097] Identify the operating status of all bidirectional converters, number the traction substations where the bidirectional converters operating in the first traction rectification state or the second traction rectification state are located into the third group, and number the traction substations where the bidirectional converters operating in the first energy feedback state and the second energy feedback state are located into the fourth group;

[0098] For the traction substations in the third group, if the bidirectional converter operating in power control mode is connected to the busbar section I of the traction substation, K2 is reduced; if it is connected to the busbar section II of the traction substation, K2 is increased;

[0099] For the traction substation in the fourth group, if the bidirectional converter operating in power control mode is connected to the traction substation section I bus, K1 is increased; if it is connected to the traction substation section II bus, K1 is reduced.

[0100] In some embodiments, after the loads of the busbars of section I and section II of the main substation are unbalanced, the control center 3 is configured to adjust K2 and K1 through the following steps:

[0101] Identify the operating status of all bidirectional converters, number the traction substations where the bidirectional converters operating in the first traction rectification state or the second traction rectification state are located into the fifth group, and number the traction substations where the bidirectional converters operating in the first energy feedback state or the second energy feedback state are located into the sixth group;

[0102] If P z1 <P z2 :

[0103] For the traction substations in the fifth group, if the bidirectional converter operating in power control mode is connected to the busbar section I of the traction substation, K2 is increased; if it is connected to the busbar section II of the traction substation, K2 is decreased.

[0104] For the traction substations in the sixth group, if the bidirectional converter operating in power control mode is connected to the busbar section I of the traction substation, K1 is reduced; if it is connected to the busbar section II of the traction substation, K1 is increased.

[0105] If P z1 >P z2 :

[0106] For the traction substations in the fifth group, if the bidirectional converter operating in power control mode is connected to the busbar section I of the traction substation, K2 is reduced; if it is connected to the busbar section II of the traction substation, K2 is increased.

[0107] For the traction substation in the sixth group, if the bidirectional converter operating in power control mode is connected to the traction substation section I bus, increase K1; if it is connected to the traction substation section II bus, decrease K1.

[0108] It should be further explained that K1 and K2 are increased or decreased according to a fixed step size, and the step size can be set to include but is not limited to 0.01, 0.02, and 0.1.

[0109] In the embodiment of the present application, both sets of bidirectional converters in the traction substation are in power control mode.

[0110] In some embodiments, the power supply system further includes an ice melting control unit. The control center 3 is configured to determine the contact network ice melting section and ice melting duration, and to determine that the traction substations at both ends of the section are X traction substation and Y traction substation, respectively. The control center 3 is connected to the ice melting control unit.

[0111] In some embodiments, as Figure 5 As shown, the ice melting control unit is configured to perform the following steps:

[0112] Controlling the X traction substation to operate in the voltage control mode;

[0113] Control all traction substations except X traction substation to operate in power control mode;

[0114] Control the de-icing power of the two bidirectional converters in the Y traction substation, and lock them when the specified de-icing time is reached.

[0115] It needs to be further explained that, Figure 5 As shown, the catenary de-icing section and de-icing duration are determined, and the traction substations at both ends of the section are determined to be X traction substation and Y traction substation respectively;

[0116] The ice melting control unit changes the K1 and K2 of the two bidirectional converters in the X traction substation to 0.5;

[0117] The ice melting control unit controls the two bidirectional converters in the Y traction substation to unlock and operate in power control mode;

[0118] When the ice melting time is reached:

[0119] The ice melting control unit controls the power control instructions of the two bidirectional converters in the Y traction substation to 0 and locks them;

[0120] The ice melting control unit controls the voltage control command of the X traction substation to be restored to the initial value.

[0121] Accordingly, an embodiment of the present application further provides a control method for a traction power supply system based on a bidirectional converter, the control method comprising:

[0122] The control center 3 adjusts the control mode of the bidirectional converters in each traction substation;

[0123] Based on the control mode, the control center 3 monitors the loads of the busbars of section I and section II of the main substation to adjust the power ratio of the two sets of bidirectional converters in each traction substation according to the load balance.

[0124] In some embodiments, one set of bidirectional converters in the traction substation operates based on a voltage control mode, and another set of bidirectional converters in the traction substation operates based on a power control mode.

[0125] In some embodiments, as Figure 2 As shown, the bidirectional converter operates in voltage control mode and monitors the DC side voltage U in real time. dc , Control Center 3 will U dc with U set1 、U set2 For comparison, U set1 is the threshold voltage for starting the first energy feedback state, U set2 A threshold voltage for starting the first traction rectification state;

[0126] When U dc >U set1 When the voltage is controlled, the bidirectional converter is controlled to enter the first energy feedback state and the DC side voltage is controlled to be constant;

[0127] When U set2 ≤U dc ≤U set1 When , the bidirectional converter operating in the voltage control mode is controlled to enter a first no-load voltage stabilization state, and droop control is performed according to a first droop coefficient Z1;

[0128] When U dc <U set2 When , the bidirectional converter operating in the voltage control mode is controlled to enter the first traction rectification state, and droop control is performed according to the second droop coefficient Z2.

[0129] It should be further explained that the first droop coefficient Z1 and the second droop coefficient Z2 satisfy: |Z2|<|Z1|.

[0130] In some embodiments, the bidirectional converter operating in the power control mode obtains the real-time operating power P1 of the bidirectional converter operating in the voltage control mode, and the control center 3 compares P1 with P set1 、P set2 For comparison, P set1 The threshold power for starting the second energy feedback state, P set2 A threshold power for starting the second traction rectification state;

[0131] When P set1 ≤P1≤P set2 When the power is controlled, the bidirectional converter operating in the power control mode is controlled to enter the locked standby state;

[0132] When P1<P set1When the power control mode is set to zero, the bidirectional converter is controlled to enter the second energy feedback state and perform constant power control according to the first power control instruction P_hk;

[0133] Specifically, P_hk=K1*(P1+P2), where K1 is the load balancing coefficient of the two bidirectional converters in the energy feedback state, and P2 is the operating power of the bidirectional converter operating in the power control mode, and 0≤K1≤1;

[0134] When P1>P set2 When the bidirectional converter operating in the power control mode is controlled to enter the second traction rectification state, and constant power control is performed according to the second power control instruction P_qy.

[0135] Specifically, P_qy=K2*(P1+P2), K2 is the load balancing coefficient of the two sets of bidirectional converters in the traction rectification state, and 0≤K2≤1.

[0136] In the embodiment of the present application, when the control center 3 performs ice-melting operation on the ice-melting control unit, both sets of bidirectional converters in the traction substation are in the power control mode.

[0137] In some embodiments, the overhead contact network of the ground traction substation is prone to ice accumulation in winter. When the subway regenerative power processing device of the adjacent traction substation performs ice melting on the overhead contact network at night: on the one hand, a switching operation is required to disconnect the electrical connection between the overhead contact network of the deicing section and other overhead contact networks to avoid circulation between the equipment of the deicing station and other station equipment; on the other hand, since the subway regenerative power processing device is connected to different sections of the busbar, the power loss during the deicing process is large, and the main load is low at night, which easily causes active power reverse transmission. To solve the above problems, the specific steps for the deicing control unit to perform deicing are as follows:

[0138] The user determines the section and duration of catenary de-icing according to the needs, and determines the X traction substation and Y traction substation at both ends of the section;

[0139] Control X traction substation to operate in voltage control mode;

[0140] The ice melting control unit controls the bidirectional converters of all traction substations except the X traction substation to operate in power control mode;

[0141] The de-icing control unit controls the voltage control mode of the X traction substation. The voltage control instruction of the bidirectional converter is U rb , 1700V<U rb <1900V; For the bidirectional converter in power control mode of X traction substation, both K1 and K2 are modified to 0.5;

[0142] The ice melting control unit controls the two bidirectional converters of Y traction substation to unlock and operate in power control mode. The power control command is Prb , the power direction flows from the DC side to the AC side, 0≤|P rb |≤P N , P N is the long-term rated power of the bidirectional converter;

[0143] When the de-icing time is reached, the de-icing control unit first reduces the de-icing power of the two bidirectional converters in the Y traction substation to 0 and locks them. Then, it restores the control voltage command of the X traction substation to the initial value. Finally, except for the X traction substation, the bidirectional converters in other traction substations return to the initial control mode.

[0144] In summary, the operating power ratio between the two sets of bidirectional converters in the traction substation in this application is adjustable, effectively solving the load imbalance and active power reverse transmission problems of the main substation 13. This power supply system is suitable for subway lines where all trains have eliminated onboard resistors. Compared with the method of adjusting the starting threshold of adjacent stations, it reduces overhead line losses and eliminates overhead line voltage fluctuations.

[0145] This application achieves de-icing of the catenary of adjacent traction substations and reduces de-icing losses by controlling the operating mode of the bidirectional converter without switching operations;

[0146] In this application, the bidirectional converter in the controlled power mode of the traction substation is in a locked state when there is no train braking. On the one hand, it reduces the operating loss, and on the other hand, it avoids the circulation between the bidirectional converters within the station and between stations, thereby realizing the de-icing of the contact network of adjacent traction substations and reducing de-icing losses.

[0147] The present application also provides a readable storage medium on which a computer program is stored. When the computer program is executed by a processor, the above-mentioned control method is implemented.

[0148] It should be understood that the above description is for illustrative purposes only and is not intended to be limiting. Many embodiments and many applications beyond the examples provided will be apparent to those skilled in the art upon reading the above description. Therefore, the scope of the present teachings should not be determined with reference to the above description, but rather with reference to the preceding claims and the full scope of equivalents to which such claims are entitled. For the purpose of completeness, all articles and references, including disclosures of patent applications and publications, are incorporated herein by reference. The omission of any aspect of the subject matter disclosed herein from the preceding claims is not intended to be a disclaimer of such subject matter, nor should it be considered that the applicants did not consider such subject matter to be part of the disclosed subject matter.

Claims

1. A bidirectional converter traction power supply system, characterized in that: include: N traction substations, each of which is provided with two sets of bidirectional converters, the two sets of bidirectional converters being respectively connected to the corresponding AC medium-voltage power supply network traction substation section I busbar and traction substation section II busbar, the two sets of bidirectional converters in each traction substation being connected by communication, the control modes of the bidirectional converters including voltage control mode and power control mode, N is a positive integer, N ≥ 2; A main substation (13), the main substation (13) comprising a main substation section I busbar and a main substation section II busbar; A control center (3), the control center (3) being located in the main substation (13), and the control center (3) being connected to each of the bidirectional converters by communication; The control center (3) is configured to adjust the control mode of the bidirectional converter in each traction substation; and monitor the load of the main substation section I bus and the main substation section II bus based on the control mode, so as to adjust the power ratio of the two sets of bidirectional converters in each traction substation according to the load balance situation, and perform ice melting of the contact network of adjacent traction substations based on the control mode switching; In the two sets of bidirectional converters in the traction substation: One set of the bidirectional converters operates based on the voltage control mode, and the other set of the bidirectional converters operates based on the power control mode; The operating states of the bidirectional converter based on the voltage control mode include a first traction rectification state, a first energy feedback state, and a no-load voltage stabilization state; The operating states of the bidirectional converter based on the power control mode include a second traction rectification state, a second energy feedback state, and a locked standby state; The control center (3) is further configured to perform the following steps: identifying the operating status of all the bidirectional converters; For the traction substation where the bidirectional converter in the first traction rectification state or the second traction rectification state is located, the load balancing coefficient K2 of the two bidirectional converters in the traction rectification state is adjusted according to the connection relationship between the bidirectional converter operating based on the power control mode and the traction substation section I bus and the traction substation section II bus, combined with the active power reverse transmission phenomenon determination result of the main substation section I bus and the main substation section II bus or the load balance determination result of the main substation section I bus and the main substation section II bus; For the traction substation where the bidirectional converter in the first energy feedback state or the second energy feedback state is located, the load balancing coefficient K1 of the two bidirectional converters in the energy feedback state is adjusted according to the connection relationship between the bidirectional converter operating based on the power control mode and the traction substation section I bus and the traction substation section II bus, combined with the active power reverse transmission phenomenon determination result of the main substation section I bus and the main substation section II bus or the load balance determination result of the main substation section I bus and the main substation section II bus; The power supply system further includes an ice melting control unit. The control center (3) is configured to determine the contact network ice melting section and ice melting duration, and to determine that the traction substations at both ends of the section are X traction substation and Y traction substation, respectively. The control center (3) is connected to the ice melting control unit, and the ice melting control unit is configured to perform the following steps: controlling the X traction substation to operate in the voltage control mode; controlling the traction substations other than the X traction substation to operate in the power control mode; Controlling the de-icing power of the two sets of bidirectional converters in the Y traction substation, and locking both sets of converters when a predetermined de-icing time is reached; When the bidirectional converter operating in the voltage control mode fails or the AC bus to which it is connected fails, the bidirectional converter operating in the voltage control mode is configured to exit operation, and the bidirectional converter operating in the power control mode is configured to continue operating in accordance with the voltage control mode; When the bidirectional converter operating based on the power control mode fails or the AC bus to which it is connected fails, the bidirectional converter operating based on the power control mode is configured to exit operation, and the bidirectional converter operating based on the voltage control mode is configured to continue operating according to the power control mode.

2. A bidirectional converter traction power supply system according to claim 1, characterized in that: The bidirectional converter operates based on the voltage control mode, including: The bidirectional converter monitors the DC side voltage U in real time dc ; When the DC side voltage U dc Greater than the threshold voltage U for starting the first energy feedback state set1 When , the bidirectional converter enters the first energy feedback state and controls the DC side voltage to be constant.

3. A bidirectional converter traction power supply system according to claim 2, characterized in that: The bidirectional converter operates based on the power control mode, including: The bidirectional converter operating in the power control mode obtains the real-time operating power P1 of the bidirectional converter operating in the voltage control mode; When the real-time operating power P1 is less than the threshold power P for starting the second energy feedback state set1 When the bidirectional converter operates based on the power control mode, it enters the second energy feedback state and performs constant power control according to the first power control instruction P_hk. The first power control instruction P_hk is determined based on the load balancing coefficient K1 of the two sets of bidirectional converters in the energy feedback state, the real-time operating power P1 and the operating power of the bidirectional converter operating based on the power control mode.

4. A bidirectional converter traction power supply system according to claim 3, characterized in that: The bidirectional converter operates based on the power control mode, and further includes: When the real-time operating power P1 is greater than the threshold power P1 for starting the second traction rectification state set2 When the bidirectional converter operates based on the power control mode, it enters the second traction rectification state and performs constant power control according to the second power control instruction P_qy. The second power control instruction P_qy is determined based on the load balancing coefficient K2 of the two sets of bidirectional converters in the traction rectification state, the real-time operating power P1 and the operating power of the bidirectional converter operating based on the power control mode.

5. A bidirectional converter traction power supply system as claimed in claim 1, characterized in that: The power supply system further comprises a flow control unit, which is configured to monitor the bus load Pz1 of section I of the main substation and the bus load Pz2 of section II of the main substation in real time. The control center (3) is connected to the flow control unit and is further configured to perform the following steps: When the busbar load P of section I of the main substation z1 Less than the active reverse power criterion P of busbar section I of main substation zset1 When , it is determined that the active power reverse transmission phenomenon occurs on the busbar of section I of the main substation; When the busbar load P of the main substation II section z2 Less than the active reverse power criterion P of the busbar of section I of the main substation zset1 When the active power reverse transmission phenomenon occurs on the busbar of section II of the main substation; When |P z1 -P z2 |<P zset2 When P zset2 The load imbalance criterion for the busbars of section I of the main substation and section II of the main substation is used to determine that the loads of the busbars of section I of the main substation and section II of the main substation are unbalanced.

6. A control method for a bidirectional converter traction power supply system, characterized in that: The control method is used to control the bidirectional converter traction power supply system according to any one of claims 1 to 5, and the control method includes: The control center (3) adjusts the control mode of the bidirectional converters in each traction substation; The control center (3) monitors the loads of the main substation section I bus and the main substation section II bus based on the control mode, so as to adjust the power ratio of the two sets of bidirectional converters in each traction substation according to the load balance situation, and performs de-icing of the contact network of adjacent traction substations based on the control mode switching.

7. The control method of a bidirectional converter traction power supply system according to claim 6, characterized in that: A set of the bidirectional converters in the traction substation operates based on a voltage control mode, and another set of the bidirectional converters in the traction substation operates based on a power control mode. The control method further includes: The bidirectional converter operating in the voltage control mode monitors the DC side voltage U in real time. dc ; If the DC side voltage U dc Greater than the threshold voltage U for starting the first energy feedback state set1 , the bidirectional converter operating based on the voltage control mode enters the first energy feedback state and controls the DC side voltage to be constant.

8. The control method of a bidirectional converter traction power supply system according to claim 7, characterized in that: include: The bidirectional converter operating in the power control mode obtains the real-time operating power P1 of the bidirectional converter operating in the voltage control mode; If the real-time operating power P1 is less than the threshold power P for starting the second energy feedback state, set1 , the bidirectional converter operating based on the power control mode enters the second energy feedback state and performs constant power control according to the first power control instruction P_hk; If the real-time operating power P1 is greater than the threshold power P1 for starting the second traction rectification state set2 , the bidirectional converter operating based on the power control mode enters the second traction rectification state and performs constant power control according to the second power control instruction P_qy.

9. A readable storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the control method according to any one of claims 6 to 8 is implemented.

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