Pre-charging method and system for traction auxiliary converter of motor train unit

Abstract

The application provides a pre-charging method and system of a motor train unit traction auxiliary converter, the method comprising: closing an output contactor in the traction auxiliary converter according to a received contactor closing instruction; if no pre-charging instruction is received, judging whether to perform a pre-charging process on a direct current capacitor in the traction auxiliary converter according to a voltage of the direct current capacitor and a preset rated voltage; if yes, obtaining three-phase alternating current voltages and three-phase alternating current of an alternating current port of an auxiliary inverter in the traction auxiliary converter, determining active current feedback values and reactive current feedback values, and generating a pulse signal, and sending the pulse signal to the auxiliary inverter, so that an output voltage of a direct current port of the auxiliary inverter reaches the rated voltage. The application realizes the pre-charging function of the converter without increasing the hardware of the converter, reduces the cost, improves the availability of the converter, reduces the current impact of the switching device and the action frequency, helps to improve the service life and reduce the failure rate.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of motor train unit traction auxiliary converter, and particularly relates to a pre-charging method and system of motor train unit traction auxiliary converter. BACKGROUND

[0002] At present, motor train unit traction converter generally adopts AC-DC-AC circuit structure. When the traction converter is put into operation, the initial value of the DC side voltage of the converter is 0V, the input side is an AC voltage, and the AC voltage is changed into a DC voltage through an uncontrolled rectifier. If the DC link capacitor is directly applied, the instantaneous impact current will be too large, so a pre-charging circuit is generally used to realize pre-charging of the DC link capacitor.

[0003] The pre-charging circuit is usually installed on the AC input side of the traction converter. The pre-charging circuit includes a pre-charging contactor and a pre-charging resistor. The pre-charging contactor and the pre-charging resistor are usually connected in series and connected in parallel with the main contactor. In order to improve the redundancy, two sets of pre-charging circuits are also arranged.

[0004] When the traction converter is started, the pre-charging contactor is first closed, the AC input voltage charges the DC link capacitor through the pre-charging resistor, the starting current is suppressed, and when the DC voltage rises to a reasonable range, the main contactor is closed, that is, the whole pre-charging process is completed. However, the pre-charging circuit contains a contactor switch with mechanical action, and once a fault occurs, the whole traction converter cannot be started. In addition, the pre-charging resistor has a heat limitation, so the number of charging times within a certain time is limited. SUMMARY

[0005] In view of the problems in the prior art, the main purpose of the embodiments of the present application is to provide a pre-charging method and system of motor train unit traction auxiliary converter, which realizes pre-charging of the converter without increasing the hardware of the converter.

[0006] In order to achieve the above purpose, the embodiments of the present application provide a pre-charging method of motor train unit traction auxiliary converter, which comprises the following steps:

[0007] According to the received contactor closing instruction sent by the train central control unit, the output contactor in the traction auxiliary converter is closed;

[0008] If the pre-charging instruction sent by the train central control unit is not received, whether the DC capacitor in the traction auxiliary converter is pre-charged is judged according to the voltage of the DC capacitor and the preset rated voltage.

[0009] If the DC capacitor is pre-charged, the three-phase AC voltage and three-phase AC current of the auxiliary inverter AC port in the traction auxiliary converter are obtained, and the active current feedback value and the reactive current feedback value are determined according to the three-phase AC voltage and three-phase AC current; wherein the AC port of the auxiliary inverter is connected with the train AC bus;

[0010] According to the rated voltage, the voltage of the DC capacitor, the active current feedback value and the reactive current feedback value, a pulse signal is generated and sent to the auxiliary inverter, so that the output voltage of the DC port of the auxiliary inverter reaches the rated voltage, and the pre-charging process is completed; wherein the DC port of the auxiliary inverter is connected with the DC capacitor.

[0011] Optionally, in an embodiment of the present application, the method further comprises:

[0012] After the voltage of the DC capacitor reaches the rated voltage, the pulse signal sent to the auxiliary inverter is stopped, and the main contactor of the input switch module in the traction auxiliary converter is closed;

[0013] According to the voltage of the catenary connected with the input switch module, the working mode of the single-phase rectifier in the traction auxiliary converter is controlled;

[0014] The auxiliary inverter is started in a grid-connected mode to supply power to the train AC bus.

[0015] Optionally, in an embodiment of the present application, the method further comprises: if a pre-charging instruction sent by the train central control unit is received, the pre-charging contactor of the input switch module in the traction auxiliary converter is closed to make the catenary connected with the input switch module pre-charge the DC capacitor.

[0016] Optionally, in an embodiment of the present application, the method further comprises:

[0017] After the DC capacitor is pre-charged by the catenary, if the voltage of the DC capacitor reaches the rated voltage, the main contactor of the input switch module in the traction auxiliary converter is closed;

[0018] According to the voltage of the catenary, the working mode of the single-phase rectifier in the traction auxiliary converter is controlled;

[0019] The auxiliary inverter is started in a soft-start mode to supply power to the train AC bus.

[0020] The application also provides a pre-charging system of a motor train unit traction auxiliary converter, which comprises a train central control unit, a plurality of traction auxiliary converters and a train AC bus connected with the traction auxiliary converters; wherein the traction auxiliary converter comprises a controller, an input switch module, a DC capacitor, an auxiliary inverter and an output module, the input switch module is connected with a catenary, the AC port of the auxiliary inverter is connected with the train AC bus through the output module, and the DC port of the auxiliary inverter is connected with the DC capacitor.

[0021] The train central control unit is used for sending a contactor closing instruction to each traction auxiliary converter, and randomly selecting one traction auxiliary converter as a first traction auxiliary converter and sending a pre-charging instruction to the first traction auxiliary converter, and taking each traction auxiliary converter except the first traction auxiliary converter as a non-first traction auxiliary converter.

[0022] After each traction auxiliary converter receives the contactor closing instruction, the output contactor in the output module of the traction auxiliary converter is closed.

[0023] After the controller in the first traction auxiliary converter receives the pre-charging instruction, the pre-charging contactor of the input switch module of the first traction auxiliary converter is closed to pre-charge the DC capacitor of the first traction auxiliary converter with the catenary; if the voltage of the DC capacitor of the first traction auxiliary converter reaches a preset rated voltage, the main contactor of the input switch module of the first traction auxiliary converter is closed; and the auxiliary inverter of the first traction auxiliary converter is started in a soft start mode to supply power to the train AC bus to pre-charge the DC capacitor of the non-first traction auxiliary converter.

[0024] The controller of the non-first traction auxiliary converter judges whether to pre-charge the DC capacitor of the non-first traction auxiliary converter according to the voltage of the DC capacitor and the rated voltage; if the DC capacitor is pre-charged, the controller of the non-first traction auxiliary converter controls the auxiliary inverter of the non-first traction auxiliary converter to start a rectification mode to make the output voltage of the DC port of the auxiliary inverter of the non-first traction auxiliary converter reach the rated voltage, and complete the pre-charging process.

[0025] Optionally, in an embodiment of the application, the controller of the non-first traction auxiliary converter is also used for acquiring three-phase AC voltage and three-phase AC current of the AC port of the auxiliary inverter of the non-first traction auxiliary converter, determining active current feedback value and reactive current feedback value according to the three-phase AC voltage and the three-phase AC current, generating a pulse signal according to the rated voltage, the voltage of the DC capacitor, the active current feedback value and the reactive current feedback value, and sending the pulse signal to the auxiliary inverter of the non-first traction auxiliary converter.

[0026] Optionally, in an embodiment of the present application, the traction auxiliary converter further comprises a single-phase rectifier, one end of the single-phase rectifier being connected with the input switch module, and the other end being connected with the DC capacitor.

[0027] Optionally, in an embodiment of the present application, the controller of the non-first traction auxiliary converter is further configured to stop sending the pulse signal to the auxiliary inverter of the non-first traction auxiliary converter and close the main contactor of the input switch module in the non-first traction auxiliary converter when the voltage of the DC capacitor of the non-first traction auxiliary converter reaches the rated voltage; control the working mode of the single-phase rectifier in the non-first traction auxiliary converter according to the voltage of the catenary; and start the auxiliary inverter in the non-first traction auxiliary converter in a grid-connected mode to supply power to the train AC bus.

[0028] Optionally, in an embodiment of the present application, the traction auxiliary converter further comprises a filter unit, the filter unit being arranged between the auxiliary inverter and the output module.

[0029] Optionally, in an embodiment of the present application, the traction auxiliary converter further comprises a motor inverter, one end of the motor inverter being connected with the DC capacitor, and the other end being connected with an external traction motor.

[0030] The present application further provides an electronic device, comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor implements the above method when executing the program.

[0031] The present application further provides a computer readable storage medium, which stores a computer program for executing the above method.

[0032] The present application realizes the pre-charging function of the converter without increasing the hardware of the converter, reduces the cost, significantly improves the availability of the converter, reduces the current impact of the switch device and the action frequency, and helps to improve the service life and reduce the failure rate. BRIEF DESCRIPTION OF DRAWINGS

[0033] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings needed in the embodiment description will be briefly introduced. 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 effort.

[0034] Figure 1 A flow chart of a pre-charging method of a traction auxiliary converter of a motor train unit according to an embodiment of the present application;

[0035] Figure 2A flow chart for connecting the non-first traction auxiliary converter to the train AC bus in the embodiment of the present application;

[0036] Figure 3 A flow chart for connecting the first traction auxiliary converter to the train AC bus in the embodiment of the present application;

[0037] Figure 4 A structure diagram of a pre-charging system of the traction auxiliary converter of the motor train unit in the embodiment of the present application;

[0038] Figure 5 A structure diagram of the traction auxiliary converter in the embodiment of the present application;

[0039] Figure 6 A structure diagram of the input switch module in the embodiment of the present application;

[0040] Figure 7 A structure diagram of the auxiliary inverter in the embodiment of the present application;

[0041] Figure 8 A structure diagram of the single-phase rectifier in the embodiment of the present application;

[0042] Figure 9 A structure diagram of the filter unit in the embodiment of the present application;

[0043] Figure 10A And Figure 10B A rectification mode diagram of the auxiliary inverter in the embodiment of the present application. DETAILED DESCRIPTION

[0044] The embodiment of the present application provides a pre-charging method and system of the traction auxiliary converter of the motor train unit.

[0045] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, but not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the protection scope of the present application.

[0046] As Figure 1 shown is a flow chart of the pre-charging method of the traction auxiliary converter of the motor train unit in the embodiment of the present application. The execution subject of the pre-charging method of the traction auxiliary converter of the motor train unit provided by the embodiment of the present application includes but is not limited to the controller in the traction auxiliary converter. The method shown in the figure includes:

[0047] Step S1, according to the received contactor closing instruction sent by the train central control unit, the output contactor in the traction auxiliary converter is closed.

[0048] Step S2, if the pre-charging instruction sent by the train central control unit is not received, whether the DC capacitor is pre-charged is determined according to the voltage of the DC capacitor in the traction auxiliary converter and the preset rated voltage.

[0049] Step S3, if the DC capacitor is pre-charged, the three-phase AC voltage and the three-phase AC current of the AC port of the auxiliary inverter in the traction auxiliary converter are obtained, and the active current feedback value and the reactive current feedback value are determined according to the three-phase AC voltage and the three-phase AC current; wherein the AC port of the auxiliary inverter is connected with the train AC bus.

[0050] Step S4, according to the rated voltage, the voltage of the DC capacitor, the active current feedback value and the reactive current feedback value, a pulse signal is generated and sent to the auxiliary inverter, so that the output voltage of the DC port of the auxiliary inverter reaches the rated voltage, and the pre-charging process is completed; wherein the DC port of the auxiliary inverter is connected with the DC capacitor.

[0051] Wherein, the controller in the traction auxiliary converter receives the contactor closing instruction sent by the train central control unit, and then closes the output contactor in the traction auxiliary converter. Specifically, the traction auxiliary converter includes an output module, and the output contactor is arranged in the output module. The output module is connected with the train AC bus.

[0052] Further, if the controller does not receive the pre-charging instruction sent by the train central control unit, it means that this traction auxiliary converter is not the first traction auxiliary converter for pre-charging, which is referred to as non-first traction auxiliary converter. The first traction auxiliary converter for pre-charging, which is referred to as first traction auxiliary converter, will pre-charge the DC capacitor through the external catenary according to the pre-charging instruction sent by the train central control unit.

[0053] Further, if the controller of the traction auxiliary converter does not receive the pre-charging instruction sent by the train central control unit, it means that the first traction auxiliary converter has completed the pre-charging and has been connected with the train AC bus at this time, that is, the train AC bus has 380V three-phase AC power at this time. At this time, since the output contactors of all traction auxiliary converters connected with the train AC bus are closed, the non-first traction auxiliary converter can pre-charge the DC capacitor through the train AC bus.

[0054] Further, if the voltage of the DC capacitor in the non-first traction auxiliary converter does not reach the preset rated voltage after pre-charging through the train AC bus, the non-first traction auxiliary converter needs to be pre-charged again through the auxiliary inverter to make the voltage of the DC capacitor reach the rated voltage.

[0055] In the embodiment, the controller of the non-first traction auxiliary converter acquires three-phase AC voltage and three-phase AC current of the auxiliary inverter AC port, wherein the auxiliary inverter AC port is electrically connected with the output module, and thus the three-phase AC voltage and the three-phase AC current of the auxiliary inverter AC port are the three-phase AC voltage and the three-phase AC current on the train AC bus.

[0056] In the embodiment, the controller of the non-first traction auxiliary converter acquires three-phase AC voltage and three-phase AC current of the auxiliary inverter AC port, wherein the auxiliary inverter AC port is electrically connected with the output module, and thus the three-phase AC voltage and the three-phase AC current of the auxiliary inverter AC port are the three-phase AC voltage and the three-phase AC current on the train AC bus.

[0057] Further, after the auxiliary inverter works in the rectification mode, the DC capacitor of the non-first traction auxiliary converter is continuously pre-charged through the train AC bus until the voltage of the DC capacitor reaches the rated voltage value, the controller stops sending the pulse signal to the auxiliary inverter, and thus the pre-charging process of the non-first traction auxiliary converter is completed.

[0058] As an embodiment of the present application, as shown in Figure 2 The method further includes:

[0059] Step S21, after the voltage of the DC capacitor reaches the rated voltage, the pulse signal is stopped from being sent to the auxiliary inverter, and the main contactor of the input switch module in the traction auxiliary converter is closed;

[0060] Step S22, the working mode of the single-phase rectifier in the traction auxiliary converter is controlled according to the voltage of the catenary connected with the input switch module;

[0061] Step S23, the auxiliary inverter is started in the grid-connected mode to supply power to the train AC bus.

[0062] In the embodiment, the controller of the non-first traction auxiliary converter acquires three-phase AC voltage and three-phase AC current of the auxiliary inverter AC port, wherein the auxiliary inverter AC port is electrically connected with the output module, and thus the three-phase AC voltage and the three-phase AC current of the auxiliary inverter AC port are the three-phase AC voltage and the three-phase AC current on the train AC bus.

[0063] Further, the input switch module of the non-first traction auxiliary converter is connected with the catenary, and the working mode of the single-phase rectifier in the non-first traction auxiliary converter is adjusted according to the voltage of the catenary. Specifically, due to the fluctuation of the voltage of the catenary, the working mode of the single-phase rectifier includes a starting working state and a non-empty rectification state.

[0064] Further, the non-first traction auxiliary converter completes the pre-charging, and the auxiliary inverter thereof starts to work in a grid-connected mode to supply power to the train AC bus.

[0065] As an embodiment of the present application, the method further comprises: if the pre-charging instruction sent by the train central control unit is received, closing the pre-charging contactor of the input switch module of the traction auxiliary converter to pre-charge the DC capacitor connected with the input switch module by the catenary.

[0066] If the controller receives the pre-charging instruction sent by the train central control unit, it indicates that the traction auxiliary converter is the first traction auxiliary converter to be pre-charged. After receiving the pre-charging instruction, the first traction auxiliary converter closes the pre-charging contactor in the input switch module, pre-charges the DC capacitor connected with the input module by the catenary, and stops pre-charging until the voltage of the DC capacitor reaches the preset rated voltage.

[0067] In the embodiment, as shown in Figure 3 the method further comprises:

[0068] In step S31, after the pre-charging of the DC capacitor by the catenary, if the voltage of the DC capacitor reaches the rated voltage, the main contactor of the input switch module of the traction auxiliary converter is closed.

[0069] In step S32, the working mode of the single-phase rectifier in the traction auxiliary converter is controlled according to the voltage of the catenary.

[0070] In step S33, the auxiliary inverter is started in a soft start mode to supply power to the train AC bus.

[0071] If the voltage of the DC capacitor reaches the rated voltage, it indicates that the pre-charging of the DC capacitor of the first traction auxiliary converter is completed, and at this time, the main contactor of the input switch module of the traction auxiliary converter is closed. Specifically, the main contactor is connected in parallel with the pre-charging contactor, and the pre-charging is stopped after the main contactor is closed.

[0072] Further, according to the voltage of the catenary connected with the input switch module of the first traction auxiliary converter, the working mode of the single-phase rectifier is selected. Similarly to the non-first traction auxiliary converter, due to the possible fluctuation of the voltage of the catenary, the working mode of the single-phase rectifier includes the start working state and the non-empty rectification state.

[0073] Further, the auxiliary inverter of the first traction auxiliary converter is started in a soft start mode, i.e., starting from zero and gradually increasing the established AC voltage to the rated AC voltage according to the preset slope to complete the power supply to the train AC bus.

[0074] As shown in Figure 4As shown in the structure diagram of the pre-charging system of the motor train unit traction auxiliary converter according to an embodiment of the present application, the system shown in the diagram comprises a train central control unit, a plurality of traction auxiliary converters, and a train AC bus connected with the traction auxiliary converters.

[0075] As shown in the diagram, the traction auxiliary converter comprises a controller, an input switch module, a DC capacitor, an auxiliary inverter, and an output module. Figure 5 The input switch module is connected with the overhead line system, and a traction transformer can be arranged between the input switch module and the overhead line system. The AC port of the auxiliary inverter is connected with the train AC bus through the output module, and the DC port of the auxiliary inverter is connected with the DC capacitor.

[0076] The train central control unit is configured to send a contactor closing instruction to each traction auxiliary converter, and randomly selects one traction auxiliary converter as a first traction auxiliary converter and sends a pre-charging instruction to the first traction auxiliary converter, and regards each traction auxiliary converter other than the first traction auxiliary converter as a non-first traction auxiliary converter.

[0077] After each traction auxiliary converter receives the contactor closing instruction, the output contactor in the output module of the traction auxiliary converter is closed.

[0078] After the controller in the first traction auxiliary converter receives the pre-charging instruction, the pre-charging contactor of the input switch module of the first traction auxiliary converter is closed to pre-charge the DC capacitor of the first traction auxiliary converter with the overhead line system; if the voltage of the DC capacitor of the first traction auxiliary converter reaches a preset rated voltage, the main contactor of the input switch module of the first traction auxiliary converter is closed; and the auxiliary inverter in the first traction auxiliary converter is started in a soft start mode to supply power to the train AC bus, so as to pre-charge the DC capacitor in the non-first traction auxiliary converter.

[0079] The controller of the non-first traction auxiliary converter determines whether to pre-charge the DC capacitor according to the voltage and the rated voltage of the DC capacitor; if the DC capacitor is pre-charged, the controller of the non-first traction auxiliary converter controls the auxiliary inverter in the non-first traction auxiliary converter to start a rectification mode, so that the output voltage of the DC port of the auxiliary inverter reaches the rated voltage, and the pre-charging process is completed.

[0080] As an embodiment of the present application, the controller of the non-first traction auxiliary converter is further configured to acquire three-phase AC voltage and three-phase AC current of the AC port of the auxiliary inverter in the non-first traction auxiliary converter, and determine active current feedback value and reactive current feedback value according to the three-phase AC voltage and the three-phase AC current; generate a pulse signal according to the rated voltage, the voltage of the DC capacitor, the active current feedback value, and the reactive current feedback value, and send the pulse signal to the auxiliary inverter of the non-first traction auxiliary converter.

[0081] As an embodiment of the present application, as shown in Figure 8 The traction auxiliary converter further comprises a single-phase rectifier, one end of which is connected with the input switch module, and the other end of which is connected with the DC capacitor.

[0082] In the embodiment, the controller of the non-first traction auxiliary converter is further configured to stop sending the pulse signal to the auxiliary inverter of the non-first traction auxiliary converter and close the main contactor of the input switch module in the non-first traction auxiliary converter after the voltage of the DC capacitor of the non-first traction auxiliary converter reaches the rated voltage; control the working mode of the single-phase rectifier in the non-first traction auxiliary converter according to the voltage of the overhead line system; and start the auxiliary inverter in the non-first traction auxiliary converter in the grid-connected mode to supply power to the train AC bus.

[0083] As an embodiment of the present application, as shown in Figure 9 The traction auxiliary converter further comprises a filter unit, which is arranged between the auxiliary inverter and the output module. The filter unit comprises a three-phase isolation transformer Q1-Q6, a three-phase AC capacitor Ca-Cc and a three-phase AC inductor La-Lc.

[0084] As an embodiment of the present application, as shown in Figure 5 The traction auxiliary converter further comprises a motor inverter, one end of which is connected with the DC capacitor, and the other end of which is connected with an external traction motor.

[0085] As shown in Figure 6 The input switch module is connected in parallel with the main contactor c and is composed of a pre-charge contactor a and a pre-charge resistor b in series. The filter unit can be generally composed of a three-phase isolation transformer, a three-phase AC capacitor and a three-phase AC inductor. The output module is generally a three-phase AC contactor.

[0086] Further, as shown in Figure 7 The auxiliary inverter is a three-phase inverter power module, which converts the DC power of the DC capacitor into three-phase AC power, and connects the three-phase medium-voltage AC bus of the train through the filter unit and the output module. The voltage system includes but is not limited to 380V / 50Hz and 440V / 60Hz. The controller controls the closing and opening of the pre-charge contactor and the main contactor.

[0087] The working process of the EMU train traction auxiliary converter pre-charge system of the present application comprises:

[0088] 1) After the control power of the train is powered on, the train bus switch of the three-phase 380V AC bus of the train is closed by the central control unit of the train. At the same time, an instruction is sent to all available traction auxiliary converters to close the contactors in the output module.

[0089] 2) The optional traction auxiliary converter uses the input switch module to complete the pre-charge. First, the pre-charge contactor is closed, the AC input voltage charges the DC link capacitor through the pre-charge resistor, and when the DC voltage rises above the design threshold, the main contactor is closed to complete the pre-charge of the traction auxiliary converter.

[0090] 3) According to whether the grid voltage is high enough and the demand of the train application working condition, the single-phase rectifier can start to work or work in the uncontrolled rectification state. The single-phase rectifier converts the AC power input by the traction auxiliary converter into DC power on the high-voltage DC capacitor.

[0091] 4) The auxiliary inverter of the first traction auxiliary converter starts to work in the soft start mode, that is, gradually increases the AC voltage from 0 to the rated voltage according to a certain slope to supply power to the three-phase 380V AC bus of the train. For the traction auxiliary converter whose contactor in the output module is closed, the auxiliary inverter works in the rectification state and can convert the AC power of the three-phase 380V AC bus into DC power. Therefore, with the soft start process of the auxiliary inverter of the first traction auxiliary converter, that is, the charging process of the DC capacitor of all the other traction auxiliary converters.

[0092] 5) After the DC capacitor voltage of the non-first traction auxiliary converter is established, the relationship between the DC voltage and the grid voltage is evaluated. If the amplitude of the DC voltage is higher than the proportion X of the theoretical maximum DC voltage corresponding to the grid voltage, the main contactor is closed to complete the pre-charge process. If the amplitude of the DC voltage is lower than the proportion X of the theoretical maximum DC voltage corresponding to the grid voltage, the auxiliary inverter is started to work in the rectifier mode. In this mode, the control loop is divided into a DC voltage outer loop and an AC current inner loop. The DC command voltage can be directly set as the rated DC voltage of the converter or set as the DC voltage at the starting moment and increased to the rated DC voltage of the converter at a certain slope to achieve the purpose of reducing the charging current impact. After the DC voltage reaches the rated voltage, the auxiliary inverter pulse is blocked, the main contactor is closed, and the pre-charge process of the traction auxiliary converter is completed.

[0093] 6) According to whether the grid voltage is high enough and the demand of the train application working condition, the single-phase rectifier can start to work or work in the uncontrolled rectification state. The auxiliary inverter starts to work in the grid-connected mode to supply power to the three-phase 380V AC bus.

[0094] In a specific embodiment of the present application, as shown in Figure 4 and Figure 5As shown, the specific hardware components include: a train central control unit, which realizes traction auxiliary converter input switch module and train bus switch control. The train bus switch can realize the function of breaking the bus. The traction auxiliary converter includes: a controller, an input switch module, a single-phase rectifier, a DC capacitor, an auxiliary inverter, a motor inverter, a filter unit, and an output module. The traction auxiliary converter controller mainly realizes communication with the train central control unit and the closing and opening of the pre-charging contactor and the main contactor; the input switch module realizes the pre-charging method, which is mainly composed of a pre-charging contactor a and a pre-charging resistor b connected in series, and is connected in parallel with a main contactor c, as shown in Figure 6 The single-phase rectifier is composed of an H-bridge power circuit, which realizes the conversion between AC and DC, as shown in Figure 8 The DC capacitor realizes the voltage support and filtering function; the auxiliary inverter is a three-phase inverter power module, which converts the DC power of the DC capacitor into three-phase AC power, as shown in Figure 7 The filter unit and the output module are connected to the three-phase medium-voltage AC bus of the train. The filter unit is composed of a three-phase isolation transformer, a three-phase AC inductor, and a three-phase AC capacitor, as shown in Figure 9 The output module is an output contactor, which realizes the connection and disconnection with the AC bus.

[0095] In this embodiment, the pre-charging process specifically includes:

[0096] Step 1: After the train is controlled to be powered on, the train central control unit closes the train bus switch and closes the contactor in the output module of the traction auxiliary converter, and ends the execution of Step 2.

[0097] Step 2: After the traction auxiliary converter input grid voltage condition is met, the train central control unit selects the first traction auxiliary converter to allow the traction auxiliary converter to pre-charge. First, close the pre-charging contactor, charge the DC link capacitor through the pre-charging resistor, and the voltage rises to the design threshold. Close the main contactor, the pre-charging of the traction auxiliary converter is completed, and the execution of Step 3 is ended.

[0098] Step 3: The single-phase rectifier of the first traction auxiliary converter starts to work or works in the uncontrolled rectification state according to whether the grid voltage is high enough and the demand of the train application working condition, and the execution of Step 4 is ended.

[0099] Step 4: The auxiliary inverter of the first traction auxiliary converter starts to work, and outputs AC voltage by using a soft start method, i.e., gradually increases the AC voltage from 0 to the rated voltage according to a certain slope, to supply power to the three-phase 380V AC bus of the train. At the same time, the auxiliary inverter output contactor of the non-first traction auxiliary converter and the train bus switch have been closed, and the three-phase 380V AC bus voltage is established. At the same time, the intermediate DC capacitor of the non-first traction auxiliary converter is charged, and the execution of Step 5 is ended.

[0100] Step 5: The three-phase 380V AC bus of the first traction auxiliary converter is established, and the train's central control unit allows other traction auxiliary converters to precharge. For non-first traction auxiliary converters, the relationship between their DC link capacitor voltage and the grid voltage is assessed. If the capacitor voltage amplitude is higher than the ratio X of the theoretical maximum DC voltage corresponding to the grid voltage, the main contactor is closed, completing the precharging process. If the capacitor voltage amplitude is less than the ratio X of the theoretical maximum DC voltage corresponding to the grid voltage, the auxiliary inverter is started and operates in rectifier mode. The DC link voltage is rectified and controlled to a set voltage value, which is set to the DC voltage at startup and increased at a certain slope to the converter's rated DC voltage to reduce charging current surges. After the DC voltage reaches the rated voltage, the auxiliary inverter pulse is blocked, the main contactor is closed, and the precharging process of this converter is completed.

[0101] Rectification mode, see Figure 10A and Figure 10B The set voltage U is taken as the DC rated voltage of the converter, and the difference between it and the actual detected DC link voltage is used as the input of PI regulator 1. The output of PI regulator 1 is used as the difference between the active power command value and the active current feedback value, which is used as the input of PI regulator 2. The difference between 0 and the reactive current feedback value is used as the input of PI regulator 3. The outputs of PI regulator 2 and PI regulator 3 are sent to the pulse generation module to form 6 auxiliary inverter pulses to drive the auxiliary inverter switching transistors. The voltage phase detection module outputs the voltage phase angle based on the three-phase AC voltage at the auxiliary inverter's AC port. The synchronous coordinate transformation module outputs the active current feedback value and the reactive current feedback value based on the voltage phase angle and the three-phase AC current at the auxiliary inverter's AC port.

[0102] Step 6: Depending on whether the grid voltage is high enough and the requirements of the train's operating conditions, the single-phase rectifier of the non-first traction auxiliary converter starts working or operates in uncontrolled rectification mode, and the auxiliary inverter starts working in grid-connected mode to supply power to the three-phase 380V AC bus.

[0103] This invention adds a pre-charge function to the converter without increasing the converter hardware, eliminating the need for two sets of pre-charge switching devices, thus improving redundancy and reducing costs. It significantly improves converter availability; when the pre-charge resistor's heat is limited, the converter can still use other methods for pre-charging. It reduces current surges and operating frequency in the input switching module, contributing to longer lifespan and a lower failure rate.

[0104] The principles and implementation manners of the present application are described by using specific examples, and the above examples are only used for helping to understand the method of the present application and its core idea; meanwhile, for the general technical personnel in the art, according to the idea of the present application, the specific implementation manners and application ranges will be changed, and the above description should not be understood as the limitation of the present application.

Claims

1. A method for pre-charging a traction auxiliary converter of a multiple unit train, characterized in that, The method comprises: According to the received contactor closing instruction sent by the train central control unit, the output contactor in the traction auxiliary converter is closed; If no pre-charging instruction sent by the train central control unit is received, whether the DC capacitor in the traction auxiliary converter is pre-charged is determined according to the voltage of the DC capacitor and the preset rated voltage; If the DC capacitor is pre-charged, the three-phase AC voltage and three-phase AC current of the AC port of the auxiliary inverter in the traction auxiliary converter are obtained, and the active current feedback value and the reactive current feedback value are determined according to the three-phase AC voltage and three-phase AC current; wherein the AC port of the auxiliary inverter is connected with the train AC bus; If the pre-charging instruction sent by the train central control unit is received, the pre-charging contactor of the input switch module in the traction auxiliary converter is closed, so that the contact net connected with the input switch module pre-charges the DC capacitor; According to the rated voltage, the voltage of the DC capacitor, the active current feedback value and the reactive current feedback value, a pulse signal is generated and sent to the auxiliary inverter, so that the output voltage of the DC port of the auxiliary inverter reaches the rated voltage, and the pre-charging process is completed; wherein the DC port of the auxiliary inverter is connected with the DC capacitor.

2. The method of claim 1, wherein, The method further comprises: After the voltage of the DC capacitor reaches the rated voltage, the pulse signal is stopped from being sent to the auxiliary inverter, and the main contactor of the input switch module in the traction auxiliary converter is closed; According to the voltage of the contact net connected with the input switch module, the working mode of the single-phase rectifier in the traction auxiliary converter is controlled; The auxiliary inverter is started in grid-connected mode to supply power to the train AC bus.

3. The method of claim 1, wherein, The method further comprises: After the DC capacitor is pre-charged by the contact net, if the voltage of the DC capacitor reaches the rated voltage, the main contactor of the input switch module in the traction auxiliary converter is closed; According to the voltage of the contact net, the working mode of the single-phase rectifier in the traction auxiliary converter is controlled; The auxiliary inverter is started in soft-start mode to supply power to the train AC bus.

4. A pre-charge system of a traction auxiliary converter of a motor train unit, characterized in that, The system comprises a train central control unit, a plurality of traction auxiliary converters, and a train AC bus connected with the traction auxiliary converters; wherein the traction auxiliary converter comprises a controller, an input switch module, a DC capacitor, an auxiliary inverter and an output module, the input switch module is connected with the contact net, the AC port of the auxiliary inverter is connected with the train AC bus through the output module, and the DC port of the auxiliary inverter is connected with the DC capacitor; The train central control unit is used to send a contactor closing instruction to each traction auxiliary converter, and randomly selects one traction auxiliary converter as the first traction auxiliary converter to send a pre-charging instruction to it, and takes each traction auxiliary converter except the first traction auxiliary converter as a non-first traction auxiliary converter; After each traction auxiliary converter receives the contactor closing instruction, the output contactor in the output module thereof is closed; The controller in the first traction auxiliary converter receives the pre-charging instruction, closes a pre-charging contactor of an input switch module thereof to pre-charge a DC capacitor of the catenary, closes a main contactor of the input switch module of the first traction auxiliary converter if a voltage of the DC capacitor of the first traction auxiliary converter reaches a preset rated voltage, and starts an auxiliary inverter in the first traction auxiliary converter in a soft start mode to supply power to an AC bus of the train to pre-charge a DC capacitor in a non-first traction auxiliary converter. The controller of the non-first traction auxiliary converter determines whether to pre-charge the DC capacitor according to a voltage of the DC capacitor and the rated voltage, and controls the auxiliary inverter in the non-first traction auxiliary converter to start a rectification mode to make an output voltage of a DC port of the auxiliary inverter reach the rated voltage to complete the pre-charging if the DC capacitor is pre-charged.

5. The system of claim 4, wherein, The controller of the non-first traction auxiliary converter further acquires three-phase AC voltages and three-phase AC currents of an AC port of the auxiliary inverter, determines active current feedback values and reactive current feedback values according to the three-phase AC voltages and the three-phase AC currents, generates a pulse signal according to the rated voltage, the voltage of the DC capacitor, the active current feedback values and the reactive current feedback values, and sends the pulse signal to the auxiliary inverter of the non-first traction auxiliary converter.

6. The system of claim 4, wherein, The traction auxiliary converter further comprises a single-phase rectifier, one end of the single-phase rectifier being connected with the input switch module and the other end being connected with the DC capacitor.

7. The system of claim 6, wherein, The controller of the non-first traction auxiliary converter further stops sending the pulse signal to the auxiliary inverter of the non-first traction auxiliary converter and closes a main contactor of an input switch module in the non-first traction auxiliary converter when the voltage of the DC capacitor of the non-first traction auxiliary converter reaches the rated voltage, controls a working mode of the single-phase rectifier in the non-first traction auxiliary converter according to a voltage of the catenary, and starts the auxiliary inverter in the non-first traction auxiliary converter in a grid-connected mode to supply power to the AC bus of the train.

8. The system of claim 4, wherein, The traction auxiliary converter further comprises a filter unit, the filter unit being arranged between the auxiliary inverter and the output module.

9. The system of claim 4, wherein, The traction auxiliary converter further comprises a motor inverter, one end of the motor inverter being connected with the DC capacitor and the other end being connected with an external traction motor.

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