Rail transit traction power supply system and control method

Abstract

The application discloses a rail transit traction power supply system and a control method, comprising: at least one main substation, N traction substations connected with the main substation through an AC loop network; wherein each traction substation comprises a power transformer, a bidirectional converter, an energy storage device, an AC circuit breaker, a first circuit breaker and a second circuit breaker; the high-voltage side of the power transformer is connected with the AC loop network through the AC circuit breaker, and the low-voltage side is connected with the AC side of the bidirectional converter; the DC side of the bidirectional converter is connected with the DC overhead line through the first circuit breaker, and is connected with the energy storage device through the second circuit breaker. The rail transit traction power supply system of the application completely eliminates the no-load loss problem of the bidirectional converter, reduces the system cost, improves the system energy-saving effect and peak load shifting effect, and improves the system power supply reliability.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of rail transit power supply technology, and in particular to a rail transit traction power supply system and a control method. BACKGROUND

[0002] The domestic and foreign urban rail transit power supply usually adopts DC1500V or DC750V power supply, and usually adopts a diode rectifier to take power from a 35KV or 10KV alternating current power grid, and one traction substation is usually composed of two 12-pulse rectifiers to form a 24-pulse rectifier group for DC catenary power supply. At the same time, in response to the call of the state for energy saving and emission reduction, in order to avoid the consumption of braking energy through resistance, the energy feedback device is more and more widely used in the subway line. The energy feedback device is a feedback branch connected in parallel with the rectifier group loop, which is used to feed back the train braking energy to the alternating current power grid, so as to realize the secondary utilization of energy.

[0003] The topological structure of the conventional urban rail transit traction power supply system mainly has the following types:

[0004] Figure 1 The first power supply system topological structure shown in the figure mainly includes a 24-pulse rectifier group and a braking energy feedback device. The topological structure is a passive power supply, the grid voltage fluctuation is large, the regenerative braking energy utilization rate is not high, the line loss is large, the power supply distance is short, and the vehicle emergency traction is not considered.

[0005] Figure 2 The second power supply system topological structure shown in the figure is a full-line configuration of a 24-pulse rectifier and an energy storage device with a DC / DC converter. On the one hand, the energy storage device needs to be set to a very large capacity, which is very poor in economy. In addition, if the system scheduling is to be realized, the energy storage device needs to be configured with a DC / DC converter, which not only increases the system cost, but also reduces the system efficiency.

[0006] Figure 3 The third power supply system topological structure shown in the figure is a full-line configuration of two sets of bidirectional converter devices, which can improve the energy saving rate of the power supply system, convert the power supply system from passive to active, and is an important development direction of the intelligentization of future urban rail transit traction power supply systems. However, the full-line configuration of bidirectional converter devices cannot solve the problem of the existing no-load circulating current, increases the line loss, and affects the stability of the power supply system. Even if the circulating current is reduced by adding a circulating current suppression algorithm, it cannot be eliminated, and the DC voltage fluctuation is large. SUMMARY

[0007] Therefore, it is necessary to provide a rail transit traction power supply system and a control method in view of the above at least one technical problem existing in the conventional traction power supply system.

[0008] In order to achieve the above object, the present application provides a rail transit traction power supply system, comprising at least one main substation, N traction substations connected with the main substation through an AC loop network, wherein,

[0009] Each traction substation comprises a power transformer, a bidirectional converter, an energy storage device, an AC circuit breaker, a first circuit breaker and a second circuit breaker; the high-voltage side of the power transformer is connected with the AC loop network through the AC circuit breaker, and the low-voltage side is connected with the AC side of the bidirectional converter; the DC side of the bidirectional converter is connected with a DC overhead line through the first circuit breaker and connected with the energy storage device through the second circuit breaker.

[0010] Preferably, the rail transit traction power supply system further comprises an energy operation and control system, one end of which is connected with a public network, and the other end is connected with the bidirectional converter and the energy storage device.

[0011] Preferably, an AC disconnector is arranged between the AC circuit breaker and the AC loop network; and a DC disconnector is arranged between the first circuit breaker and the DC overhead line.

[0012] Preferably, the storage medium of the energy storage device is any one of a super capacitor, a lithium battery and a flywheel energy storage device.

[0013] Preferably, the bidirectional converter is a four-quadrant converter composed of thyristors or IGBT devices.

[0014] Preferably, the rail transit traction power supply system comprises two main substations, i.e. a first main substation and a second main substation, and a bus tie switch is arranged between the AC loop network corresponding to the first main substation and the AC loop network corresponding to the second main substation.

[0015] In addition, the present application further provides a control method based on the above rail transit traction power supply system, comprising:

[0016] detecting whether the voltage of the energy storage device matches the no-load network voltage of the DC overhead line;

[0017] when the voltage of the energy storage device matches the no-load network voltage of the DC overhead line, determining that the traction substation is in a no-load state, closing the second circuit breaker, blocking the pulse of the bidirectional converter, and controlling the bidirectional converter to enter a standby state;

[0018] detecting whether the working mode of the traction substation changes;

[0019] When the working mode of the traction substation changes, the AC circuit breaker is closed, and the bidirectional converter charges the energy storage device; when the voltage of the energy storage device reaches the normal voltage of the DC catenary, the pulse of the bidirectional converter is blocked, and the bidirectional converter enters a standby state;

[0020] When the traction substation enters the traction mode, the DC catenary is powered by the energy storage device and / or the bidirectional converter;

[0021] When the traction substation enters the braking mode, the voltage of the DC catenary is fed back to the AC ring network by the bidirectional converter.

[0022] Preferably, after detecting whether the voltage of the energy storage device matches the no-load voltage of the DC catenary, the method further comprises:

[0023] When the voltage of the energy storage device does not match the no-load voltage of the DC catenary, the second circuit breaker and the AC circuit breaker are closed, the bidirectional converter is started to adjust the voltage of the energy storage device, and the step of detecting whether the voltage of the energy storage device matches the no-load voltage of the DC catenary is returned.

[0024] Preferably, after detecting whether the traction substation changes state, the method further comprises:

[0025] When the working mode of the traction substation does not change, the first circuit breaker is closed, and the DC catenary is powered by the energy storage device.

[0026] Preferably, the rail transit traction power supply system further comprises an energy operation and control system, one end of the energy operation and control system is connected to the public network, and the other end is connected to the bidirectional converter and the energy storage device; when the rail transit traction power supply system further comprises an energy operation and control system, one end of the energy operation and control system is connected to the public network, and the other end is connected to the bidirectional converter and the energy storage device, the control method of the rail transit traction power supply system further comprises:

[0027] The energy operation and control system collects the reactive power condition and power fluctuation condition of the public network, and schedules the bidirectional converter and the energy storage device of the traction substation to work according to the reactive power condition and the power fluctuation condition.

[0028] Preferably, the control method of the rail transit traction power supply system further comprises:

[0029] Determining the maintenance mode of the system; wherein the maintenance mode of the system includes a functional maintenance mode and a safety maintenance mode;

[0030] When the system is in the functional maintenance mode, the bidirectional converter and the energy storage device are independently controlled or cooperatively controlled by the closing of the second circuit breaker and the AC circuit breaker;

[0031] When the system is in the safety maintenance mode, the bidirectional converter is started to discharge the energy storage device until the voltage of the energy storage device reaches a safe voltage.

[0032] From the above, the rail transit traction power supply system has the following beneficial effects:

[0033] 1) The present application provides a new rail transit traction power supply system based on bidirectional converter and energy storage device, which innovates the traction power supply system, realizes the effects of system cost reduction, power quality improvement and system energy saving;

[0034] 2) Compared with the traditional traction power supply system based on 24-pulse diode rectifier group and energy feedback device, or diode rectifier group and energy storage device, or full-line bidirectional converter, the rail transit traction power supply system reduces voltage fluctuation and occupies less land, simplifies the traction power supply system, and realizes bidirectional control of energy;

[0035] 3) When the traction substation works in the idle mode, the bidirectional converter blocks the pulse into standby state, and the energy storage device supplies power to the DC catenary, and when the traction substation works in the traction mode, the bidirectional converter can cooperate with the energy storage device to supply power to the train, effectively eliminating the idle loss of the bidirectional converter;

[0036] 4) The rail transit traction power supply system of the present application can quickly respond to train traction and braking energy by directly hanging the energy storage device on the DC catenary, and compared with the traditional traction power supply system, the response speed is faster, the peak clipping and valley filling effect is better, and at the same time, the train can be urgently tractioned when the bidirectional converter fails, improving the system power supply reliability;

[0037] 5) The rail transit traction power supply system of the present application separates the bidirectional converter and the energy storage device by the AC circuit breaker and the second circuit breaker, and they can work independently or cooperatively, further improving the system power supply reliability. BRIEF DESCRIPTION OF DRAWINGS

[0038] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following will briefly introduce the drawings needed to be used in the embodiments or prior art description. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor.

[0039] Figure 1 It is the first kind of topology structure diagram of the conventional traction power supply system of the present application;

[0040] Figure 2 This is a second topology diagram of the conventional traction power supply system of the present invention;

[0041] Figure 3 This is a third topology diagram of the conventional traction power supply system of the present invention;

[0042] Figure 4 This is a schematic diagram of the structure of a rail transit traction power supply system in one embodiment of the present invention. Figure 1 ;

[0043] Figure 5 This is a schematic diagram of the structure of a rail transit traction power supply system in one embodiment of the present invention. Figure 2 ;

[0044] Figure 6 This is a flowchart illustrating the control method of a rail transit traction power supply system according to an embodiment of the present invention. Figure 1 ;

[0045] Figure 7 This is a flowchart illustrating the control method of a rail transit traction power supply system according to an embodiment of the present invention. Figure 2 ;

[0046] Figure 8 This is a schematic diagram illustrating the collaborative operation control principle of a bidirectional converter throughout the entire line, according to one embodiment of the present invention.

[0047] The numbers in the diagram represent: 1-power transformer, 2-bidirectional converter, 3-energy storage device, 4-AC circuit breaker, 5-first circuit breaker, 6-second circuit breaker, 7-energy operation and control system, 8-bus tie switch. Detailed Implementation

[0048] To make the technical problems to be solved, the technical solutions, and the beneficial effects of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the present invention and are not intended to limit the present invention.

[0049] The following are explanations of some of the terms used in this invention:

[0050] IGBT stands for Insulated Gate Bipolar Transistor.

[0051] like Figure 4As shown in the embodiment, the present application provides a rail transit traction power supply system, comprising: at least one main substation, N traction substations connected with the main substation through an AC ring network; wherein each traction substation comprises: a power transformer 1, a bidirectional converter 2, an energy storage device 3, an AC circuit breaker 4, a first circuit breaker 5 and a second circuit breaker 6; the high-voltage side of the power transformer 1 is connected with the AC ring network through the AC circuit breaker 4, and the low-voltage side is connected with the AC side of the bidirectional converter 2; the DC side of the bidirectional converter 2 is connected with the DC contact network through the first circuit breaker 5, and is connected with the energy storage device 3 through the second circuit breaker 6.

[0052] It can be understood that the rail transit traction power supply system can include at least one main substation and N traction substations. For each main substation, one end is connected with the public network, and the other end is connected with M traction substations through an AC ring network.

[0053] For each traction substation, it mainly includes three loops:

[0054] The AC side of the AC circuit breaker 4 is connected with the AC ring network through the power transformer 1 and the AC circuit breaker 4 in turn, and the DC side of the AC circuit breaker 4 is connected with the DC contact network through the first circuit breaker 5, forming a first traction loop; the first traction loop is used for independently or cooperatively supplying traction power to the DC contact network through the bidirectional converter 2 when the traction substation works in traction mode, and is used for feeding back the voltage of the DC contact network to the AC ring network through the bidirectional converter 2 when the traction substation works in braking mode.

[0055] The energy storage device 3 is connected with the DC contact network through the first circuit breaker 5 and the second circuit breaker 6 in turn, forming a second traction loop; the second traction loop is used for supporting the voltage of the DC contact network through the energy storage device 3 when the traction substation works in idle mode, and is used for independently or cooperatively supplying traction power to the DC contact network through the energy storage device 3 when the traction substation works in traction mode; in addition, the second traction loop is also used for supplying emergency traction power to the DC contact network through the energy storage device 3 when the AC circuit breaker 4 fails.

[0056] The energy storage device 3 is connected with the AC ring network through the second circuit breaker 6, the bidirectional converter 2, the power transformer 1 and the AC circuit breaker 4 in turn, forming a charge-discharge loop; the charge-discharge loop is used for voltage regulation of the energy storage device 3 through the bidirectional converter 2.

[0057] Further, the rated voltage of the public network is 110KV, the rated voltage of the AC ring network is 35KV, and the rated voltage of the DC contact network is 1500V or 750V.

[0058] As can be seen from the above, the rail transit traction power supply system provided by the embodiment has the following beneficial effects:

[0059] 1) The embodiment provides a brand-new rail transit traction power supply system based on bidirectional converter and energy storage device, which innovates the traction power supply system, realizes system cost reduction, power quality improvement and system energy saving effect;

[0060] 2) Compared with the traditional traction power supply system based on 24-pulse diode rectifier group and energy feedback device, or diode rectifier group and energy storage device, or full-line bidirectional converter, the rail transit traction power supply system of the embodiment reduces voltage fluctuation and occupies less land, simplifies the traction power supply system, and realizes bidirectional control of energy.

[0061] 3) When the traction substation works in the idle mode, the bidirectional converter 2 blocks the pulse to enter the standby state, and the energy storage device 3 supplies power to the DC support network, and when the traction substation works in the traction mode, the bidirectional converter 2 can cooperate with the energy storage device 3 to supply power to the train, effectively eliminating the idle loss of the bidirectional converter.

[0062] 4) The rail transit traction power supply system of the embodiment can quickly respond to train traction and braking energy through the direct-current contact network directly hanging the energy storage device 3, and compared with the traditional traction power supply system, the response speed is faster, the peak clipping and valley filling effect is better, and at the same time, the train can be urgently tractioned when the bidirectional converter fails, improving the system power supply reliability.

[0063] 5) The rail transit traction power supply system of the embodiment separates the bidirectional converter 2 and the energy storage device 3 through the alternating current circuit breaker 4 and the second circuit breaker 6, and the two can work independently or cooperatively, further improving the system power supply reliability.

[0064] 6) The rail transit traction power supply system of the embodiment sets the full-line distributed energy storage device 3, which can effectively suppress the vehicle impact load, reduce the peak power demand, and improve the system efficiency.

[0065] In an embodiment, as shown in Figure 5 The rail transit traction power supply system further comprises an energy operation and control system 7, one end of the energy operation and control system 7 is connected with the public network, and the other end is connected with the bidirectional converter 2 and the energy storage device 3. In the embodiment, the rail transit traction power supply system collects the PT signal (transformer signal) or CT signal (current transformer signal) of the public network through the energy operation and control system 7, analyzes the reactive power and power fluctuation of the public network, and adjusts the bidirectional converter 2 and the energy storage device 3 according to the reactive power and power fluctuation, thereby reducing the system power demand fluctuation and reducing the impact on the power grid.

[0066] Further, the storage medium of the energy storage device 3 is any one of super capacitor, lithium battery and flywheel energy storage. In the embodiment, the capacity of the energy storage device 3 only needs to be one third to one half of the capacity of the conventional regenerative braking energy storage device, which reduces the investment cost and improves the economic efficiency.

[0067] Further, the AC circuit breaker 4 is provided with an AC disconnector between the AC loop network, and the first circuit breaker 5 is provided with a DC disconnector between the DC contact network. In the embodiment, the AC disconnector is used to connect or cut off the voltage on the AC side, and the DC disconnector is used to connect or cut off the voltage on the DC side, which can improve the safety of the system.

[0068] Further, the bidirectional converter 2 is a four-quadrant converter composed of thyristor or IGBT device. In the embodiment, the bidirectional converter 2 can realize the bidirectional flow of energy between AC 35KV and DC 1500V, or AC 35KV and DC 750V. It should be noted that the bidirectional converter 2 is not limited to the name, and includes all controlled PWM converters that realize the bidirectional flow of energy.

[0069] Further, as shown in Figure 5 , the rail transit traction power supply system comprises two main substations, and the two main substations comprise a first main substation and a second main substation. The AC loop network corresponding to the first main substation and the AC loop network corresponding to the second main substation are provided with a bus tie switch 8. In the embodiment, the two AC loop networks are connected through the bus tie switch 8. When the first main substation and the second main substation are both in a normal working state, the bus tie switch 8 is open, and when any one of the first main substation and the second main substation is in an abnormal working state, the bus tie switch 8 is closed to supply power to the traction substation under the other main substation.

[0070] In addition, as shown in Figure 6 , the embodiment of the present application also provides a control method for the rail transit traction power supply system in the above-mentioned embodiments, which comprises the following steps:

[0071] Step S10, detecting whether the voltage of the energy storage device 3 matches the no-load network voltage of the DC contact network.

[0072] As a preferred, in one aspect of the embodiment, first, according to the voltage V S of the energy storage device 3 and the no-load network voltage V DCF of the DC contact network, the voltage deviation value V d = |V S -V DCF | of the voltage V S of the energy storage device 3 and the no-load network voltage V DCF of the DC contact network is determined, and then the voltage deviation value V d is detected.d Does it not exceed the preset deviation value T? d If the voltage deviation value V d Not exceeding the preset deviation value T d That is, V d ≤T d Then determine the voltage V of energy storage device 3. S The unloaded voltage V of the DC contact network DCF Match, and proceed to step S201; while if the voltage deviation value V d Exceeding T d That is, V d >T d Then determine the voltage V of energy storage device 3. S The unloaded voltage V of the DC contact network DCF If there is a mismatch, proceed to step S202. The preset deviation value T... d According to the no-load voltage V of the DC contact network DCF Set the preset deviation rate R, that is, T d =V DCF *R.

[0073] In another aspect of this embodiment, firstly, based on the minimum limit of the no-load voltage of the DC contact network... and maximum limit Determine the range of no-load grid voltage Then the voltage V of the energy storage device 3 is measured. S Is it within the no-load network voltage range? Inside, if the voltage V of energy storage device 3 S Within the range of no-load network voltage Inside, determine the voltage V of energy storage device 3. S The unloaded voltage V of the DC contact network DCF Matching, and proceeding to step S201; while if the voltage V of energy storage device 3 S Within the range of no-load network voltage In addition, determine the voltage V of energy storage device 3. S The unloaded voltage V of the DC contact network DCF If there is a mismatch, proceed to step S202; where the minimum limit of the no-load grid voltage range is... Maximum limit

[0074] In step S201, when the voltage of the energy storage device 3 matches the no-load voltage of the DC contact network, the traction substation enters the no-load mode, closes the second circuit breaker 6, blocks the pulse of the bidirectional converter 2, and controls the bidirectional converter 2 to enter the standby state.

[0075] In step S201, after detecting the voltage V of the energy storage device 3... S The unloaded voltage V of the DC contact networkDCF When the match is confirmed, it is confirmed that the traction substation is working in the no-load mode, the second circuit breaker 6 is closed, the AC circuit breaker 4 is opened, and the pulse control of the bidirectional converter 2 is blocked to put the bidirectional converter 2 into the standby state, so as to further determine whether the working mode of the traction substation changes. The working mode of the traction substation includes the no-load mode, the traction mode and the braking mode, and the motion state of the bidirectional converter 2 includes the standby state, the rectification state and the inversion state.

[0076] In step S202, when the voltage of the energy storage device 3 does not match the no-load network voltage of the DC contact net, the second circuit breaker 6 and the AC circuit breaker 4 are closed, and the bidirectional converter 2 is started to adjust the voltage of the energy storage device 3, and the process returns to step S10.

[0077] In step S202, when the voltage V S of the energy storage device 3 does not match the no-load network voltage V DCF of the DC contact net, the second circuit breaker 6 and the AC circuit breaker 4 are closed, and the bidirectional converter 2 charges or discharges the energy storage device 3 until the voltage V S of the energy storage device 3 matches the no-load network voltage V DCF of the DC contact net. It can be understood that when the voltage V S of the energy storage device 3 is less than the minimum limit value of the no-load network voltage , the bidirectional converter 2 is controlled to enter the rectification state to charge the energy storage device 3; and when the voltage V S of the energy storage device 3 is greater than the maximum limit value of the no-load network voltage , the bidirectional converter 2 is controlled to enter the inversion state to discharge the energy storage device 3.

[0078] In step S30, it is detected whether the current working mode of the traction substation changes.

[0079] That is, after it is determined in step S201 that the traction substation enters the no-load mode, it is detected in real time whether the current working mode of the traction substation changes, and when the current working mode of the traction substation changes, step S401 is entered; and when the traction substation still works in the no-load mode, step S402 is entered.

[0080] In step S401, when the working mode of the traction substation changes, the AC circuit breaker 4 is closed, and the bidirectional converter 2 is started to charge the energy storage device 3, and when the voltage of the energy storage device 3 reaches the normal network voltage of the DC contact net, the pulse of the bidirectional converter 2 is blocked to control the bidirectional converter 2 to enter the standby state;

[0081] That is, when the current operating mode of the traction substation changes, the AC circuit breaker 4 is closed, and the bidirectional converter 2 is started. The bidirectional converter 2 is controlled to enter the rectification state to charge the energy storage device 3, while the voltage V of the energy storage device 3 is monitored in real time. S Does it reach the normal DC contact network voltage V? DCN At that time, when the voltage V of energy storage device 3 S To achieve the normal grid voltage V of the DC contact network DCN At this time, the AC circuit breaker 4 is tripped, and the pulse of the bidirectional converter 2 is blocked, controlling the bidirectional converter 2 to enter standby mode, in order to further determine whether the traction substation is operating in traction mode or braking mode after the change in operating mode. Among them, the normal grid voltage V of the DC contact network... DCN The unloaded voltage V of the DC contact network is greater than that of the DC contact network. DCF .

[0082] In step S402, when the working mode of the traction substation has not changed, the first circuit breaker 5 is closed, and the DC contact network is powered through the energy storage device 3.

[0083] That is, when the traction substation is still operating in no-load mode, only the first circuit breaker 5 is closed, and the DC contact network is powered through the independent energy storage device 3. At this time, the AC circuit breaker 4 is still in the open state.

[0084] Step S50: When the traction substation is in traction mode, the DC contact network is powered through the energy storage device 3 and / or the bidirectional converter 2.

[0085] As a preferred option, when the traction substation operates in traction mode after the change in operating mode, the DC contact network is first powered through the independent energy storage device 3. At this time, the AC circuit breaker 4 is still in the open state. Then, when it is detected that the energy storage device 3 cannot meet the power supply requirements, the AC circuit breaker 4 can be directly closed, the bidirectional converter 2 can be started, and the voltage of the AC ring network can be rectified and transmitted to the DC contact network through the bidirectional converter 2, and the energy storage device 3 can work together to power the DC contact network.

[0086] Understandably, when it is detected that the energy storage device 3 cannot meet the power supply requirements, the second circuit breaker 6 can be disconnected, the AC circuit breaker 4 can be closed, and the bidirectional converter 2 can be started to supply power to the DC contact network through the independent bidirectional converter 2.

[0087] Furthermore, in the event of a traction substation failure, the energy storage device 3 can be used to provide emergency traction for the train, thereby improving the reliability of the system's power supply.

[0088] In step S60, when the traction substation is in braking mode, the voltage feedback of the DC contact network is transmitted to the AC ring network through the bidirectional converter 2.

[0089] That is, when the traction substation works in the braking mode after the working mode changes, the second circuit breaker 6 is tripped, the AC circuit breaker 4 is closed, and the bidirectional converter 2 is started, and the voltage of the DC catenary is fed back to the AC loop network through the bidirectional converter 2.

[0090] As can be seen from the above, the control method of the rail transit traction power supply system in the embodiment can effectively eliminate the no-load loss of the bidirectional converter and improve the energy-saving effect of the system when the traction substation works in the no-load mode and the bidirectional converter 2 is blocked and the energy storage device 3 supplies power to the DC catenary, and when the traction substation works in the traction mode, the bidirectional converter 2 cooperates with the energy storage device 3 to supply power to the DC catenary. Meanwhile, the bidirectional converter 2 and the energy storage device 3 are separated by the AC circuit breaker 4 and the second circuit breaker 6, and can work independently or cooperatively, thereby improving the power supply reliability of the system.

[0091] In an embodiment, as shown in Figure 7 the control method of the rail transit traction power supply system further comprises an energy operation and control system, one end of the energy operation and control system is connected with the public network, and the other end is connected with the bidirectional converter 2 and the energy storage device 3, and the method further comprises the following steps:

[0092] Step S70, the energy operation and control system 7 collects the reactive power condition and power fluctuation condition of the public network, and schedules the bidirectional converter 2 and the energy storage device 3 of the traction substation to work according to the reactive power condition and the power fluctuation condition.

[0093] It can be understood that the bidirectional converter 2 and the energy storage device 3 wait for the scheduling work of the energy operation and control system 7, the energy operation and control system 7 obtains the reactive power condition and power fluctuation condition of the public network, and starts the bidirectional converter 2 and the energy storage device 3 of the corresponding traction substation to carry out peak clipping and valley filling. Specifically, the load characteristics of the rail transit traction system belong to pulse high-power load, when the rail vehicle brakes, correspondingly, the traction substation works in the braking mode, which can absorb the energy on the DC catenary and store it; when the rail vehicle is traction, correspondingly, the traction substation works in the traction mode, which can release the energy of the energy storage for vehicle traction, and through the storage and release of energy, the short-time overload of the station equipment can be effectively solved, and the power supply capacity demand can be reduced.

[0094] Further, as shown in Figure 8 the cooperative working control process of the full-line bidirectional converter in the embodiment is as follows:

[0095] Step one, the energy operation and control system 7 obtains the output current of the plurality of bidirectional converters 2, and obtains the current average according to the output current of all bidirectional converters 2. The calculation formula of the current average is:

[0096]

[0097] In the above formula, I avg is the average current, n is the number of bidirectional converter 2, I dci is the output current of the i-th bidirectional converter.

[0098] Step two, determine the compensation voltage of the bidirectional converter 2 according to the average current and the adjustment coefficient. The calculation formula of the compensation voltage is:

[0099] ΔU = I avg × d (2)

[0100] In the above formula, ΔU is the compensation voltage, and d is the adjustment coefficient.

[0101] Step three, input the compensation voltage into the preset droop model to obtain the target control voltage of the bidirectional converter 2. The droop model can be expressed as:

[0102] U * = U k -R dp × I dc + ΔU (3)

[0103] In the above formula, U * is the target control voltage of the bidirectional converter 2, U k is the no-load voltage; R dp is the load feed-forward voltage, and I dc is the output current of the bidirectional converter 2.

[0104] Step four, according to the target control voltage of the bidirectional converter 2 and the working state of the bidirectional converter 2, realize the no-load circulating current control or the power distribution of multiple bidirectional converters 2.

[0105] Specifically, when the vehicle is in no-load, the energy control system 7 sets the target control voltage of the bidirectional converter 2 by using the droop model, so as to limit the no-load circulating current within the preset range (I nlf ,I nft ), wherein I nlf is the minimum traction current, and I nft is the minimum braking current; when the vehicle is in traction, the energy control system 7 sets the target control voltage of the bidirectional converter 2 by using the droop model to realize the power distribution of the n bidirectional converters 2; when the vehicle is in braking, the energy control system 7 sets the target control voltage of the bidirectional converter 2 by using the droop function to realize the power distribution of the n bidirectional converters 2.

[0106] In an embodiment, the control method of the rail transit traction power supply system further comprises the following steps:

[0107] Step S801, determine the maintenance mode of the system (i.e. rail transit traction power supply system), wherein the maintenance mode of the system contains two kinds of functional maintenance mode and safety maintenance mode;

[0108] Step S802, when the system is in the functional maintenance mode, control the independent work or cooperative work of the bidirectional converter 2 and the energy storage device 3 through the closing control of the second circuit breaker 6 and the AC circuit breaker 4;

[0109] Step S803, when the system is in the safety maintenance mode, start the bidirectional converter 2 to discharge the energy storage device 3 until the voltage of the energy storage device 3 reaches the safety voltage.

[0110] It can be understood that when the system is in the functional maintenance mode, the bidirectional converter 2 and the energy storage device 3 can work independently or cooperatively, and when the bidirectional converter 2 is stopped, only the AC circuit breaker 4 needs to be tripped, and when the energy storage device 3 is stopped, only the second circuit breaker 6 needs to be tripped, which can improve the reliability of the system.

[0111] When the system is in the safety maintenance mode, the first circuit breaker 5 is tripped, the bidirectional converter 2 is started, and the energy of the energy storage device 3 is discharged to the safety range, thereby improving the operation safety of the system.

[0112] The above only describes the preferred embodiments of the present application and is not used to limit the present application, and any modification, equivalent replacement and improvement made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A control method for a rail transit traction power supply system, characterized in that, The rail transit traction power supply system includes: at least one main substation and N traction substations connected to the main substation via an AC ring network; wherein... Each traction substation includes a power transformer, a bidirectional converter, an energy storage device, an AC circuit breaker, a first circuit breaker, and a second circuit breaker. The high-voltage side of the power transformer is connected to the AC ring network via the AC circuit breaker, and the low-voltage side is connected to the AC side of the bidirectional converter. The DC side of the bidirectional converter is connected to the DC contact network via the first circuit breaker and to the energy storage device via the second circuit breaker. The control method includes: Check whether the voltage of the energy storage device matches the no-load voltage of the DC contact network; When the voltage of the energy storage device matches the no-load voltage of the DC contact network, it is determined that the traction substation is in a no-load state. The second circuit breaker is closed, the pulse of the bidirectional converter is blocked, and the bidirectional converter is controlled to enter the standby state. Detect whether the operating mode of the traction substation has changed; When the operating mode of the traction substation changes, the AC circuit breaker is closed and the bidirectional converter is started to charge the energy storage device. When the voltage of the energy storage device reaches the normal grid voltage of the DC contact network, the pulse of the bidirectional converter is blocked and the bidirectional converter is controlled to enter the standby state. When the traction substation operates in traction mode after the change in operating mode, the DC contact network is powered by the energy storage device and / or the bidirectional converter. When the traction substation operates in braking mode after the change of operating mode, the voltage feedback of the DC contact network is transmitted to the AC ring network through the bidirectional converter.

2. The control method for a rail transit traction power supply system according to claim 1, characterized in that, The rail transit traction power supply system also includes an energy operation and control system, one end of which is connected to the public grid and the other end is connected to the bidirectional converter and energy storage device.

3. The control method for the rail transit traction power supply system according to claim 2, characterized in that, An AC isolating switch is provided between the AC circuit breaker and the AC ring network; a DC isolating switch is provided between the first circuit breaker and the DC contact network.

4. The control method for a rail transit traction power supply system according to any one of claims 1 to 3, characterized in that, The energy storage medium of the energy storage device is any one of supercapacitors, lithium batteries, and flywheel energy storage.

5. The control method for a rail transit traction power supply system according to any one of claims 1 to 3, characterized in that, The bidirectional converter is a four-quadrant converter composed of thyristors or IGBT devices.

6. The control method for a rail transit traction power supply system according to any one of claims 1 to 3, characterized in that, It includes two main substations, namely a first main substation and a second main substation. The AC ring network corresponding to the first main substation and the AC ring network corresponding to the second main substation are equipped with bus tie switches.

7. The control method for a rail transit traction power supply system according to claim 1, characterized in that, After determining whether the voltage of the energy storage device matches the no-load voltage of the DC contact network, the method further includes: When the voltage of the energy storage device does not match the no-load voltage of the DC contact network, the second circuit breaker and the AC circuit breaker are closed, and the bidirectional converter is started to regulate the voltage of the energy storage device, and the process returns to the step: checking whether the voltage of the energy storage device matches the no-load voltage of the DC contact network.

8. The control method for a rail transit traction power supply system according to claim 7, characterized in that, After detecting whether a state switch has occurred at the traction substation, the method further includes: When the operating mode of the traction substation remains unchanged, the first circuit breaker is closed, and the DC contact network is powered through the energy storage device.

9. The control method for a rail transit traction power supply system according to claim 1, characterized in that, The rail transit traction power supply system also includes an energy operation and control system, one end of which is connected to the public grid, and the other end is connected to the bidirectional converter and energy storage device. The method further includes: The energy operation and control system collects the reactive power and power fluctuation information of the public grid, and schedules the bidirectional converter and energy storage device of the traction substation to work according to the reactive power and power fluctuation information.

10. The control method for a rail transit traction power supply system according to any one of claims 7 to 9, characterized in that, Also includes: Determine the maintenance mode of the system; wherein, the maintenance mode of the system includes two types: functional maintenance mode and safety maintenance mode; When the system is in the functional maintenance mode, the bidirectional converter and the energy storage device can work independently or in concert by controlling the opening and closing of the second circuit breaker and the AC circuit breaker. When the system is in the safety maintenance mode, the bidirectional converter is activated to discharge the energy storage device until the voltage of the energy storage device reaches a safe voltage.

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