Pre-charge device, system and method for a traction auxiliary converter

Abstract

The application provides a pre-charging device, system and method of a traction auxiliary converter, the device comprising: a traction auxiliary converter and a three-phase medium-voltage alternating current bus; the traction auxiliary converter comprising: a controller, an input switch module, an isolated bidirectional DCDC module, an energy storage element, a high-voltage direct-current capacitor and a medium-voltage direct-current capacitor; the controller being connected with the input switch module and the isolated bidirectional DCDC module respectively; the isolated bidirectional DCDC module being connected with the high-voltage direct-current capacitor, the medium-voltage direct-current capacitor and the energy storage element respectively; the input switch module being connected with the high-voltage direct-current capacitor; and the three-phase medium-voltage alternating current bus being connected with the medium-voltage direct-current capacitor. The application can reduce the current impact and action frequency of the switch element in the input switch module, help to improve the element life and reduce the failure rate, and thus can improve the reliability of the pre-charging of the traction converter.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of vehicle-mounted energy storage, and in particular to a pre-charging device, system and method for a traction auxiliary converter. BACKGROUND

[0002] Currently, high-speed EMU traction converters generally adopt an AC-DC-AC circuit structure of a four-quadrant rectifier plus a three-phase inverter. When the traction converter is put into operation, if the initial value of the DC voltage of the traction converter is 0V, the AC input voltage is directly applied to the DC link capacitor via an uncontrolled rectifier, which will cause a very large instantaneous impact current, thereby affecting the safety and service life of the equipment.

[0003] Therefore, a pre-charging method needs to be adopted to power on the traction converter under the condition of limited impact current; generally, a pre-charging unit is installed on the AC input side of the traction converter, which can be formed by connecting a pre-charging contactor and a pre-charging resistor in series and connected in parallel with the main contactor. When the traction converter starts, the pre-charging contactor is first closed, the AC input voltage charges the DC link capacitor through the pre-charging resistor, realizing the suppression of the starting current, and after the DC voltage rises to a high level, the main contactor is closed, that is, the entire pre-charging starting process is completed.

[0004] However, the pre-charging resistor has a heating limit, and the number of charging times within a certain time is limited; the voltage characteristics and impedance characteristics of different section catenary are different, resulting in discreteness in the pre-charging process, which makes it difficult to identify the health status of the main circuit; there is still a certain degree of current impact when the main contactor is closed, which affects the service life of the contactor. SUMMARY

[0005] In view of at least one problem in the prior art, the present application provides a pre-charging device, system and method for a traction auxiliary converter, which can reduce the current impact and action frequency of the switching elements in the input switching module, help to improve the service life of the elements and reduce the failure rate, and thus can improve the reliability of the pre-charging of the traction converter.

[0006] In order to solve the above technical problems, the present application provides the following technical solutions:

[0007] In a first aspect, the present application provides a pre-charging device for a traction auxiliary converter, comprising: a traction auxiliary converter and a three-phase medium-voltage AC bus;

[0008] The traction auxiliary converter comprises: a controller, an input switching module, an isolated bidirectional DCDC module, an energy storage element, a high-voltage DC capacitor and a medium-voltage DC capacitor;

[0009] The controller is connected with the input switch module and the isolated bidirectional DCDC module respectively; the isolated bidirectional DCDC module is connected with the high-voltage direct-current capacitor, the medium-voltage direct-current capacitor and the energy storage element respectively; the input switch module is connected with the high-voltage direct-current capacitor; the three-phase medium-voltage alternating-current bus is connected with the medium-voltage direct-current capacitor; wherein,

[0010] The controller is configured to determine to apply one of the energy storage element, the three-phase medium-voltage alternating-current bus and the input switch module to complete charging of the medium-voltage direct-current capacitor according to states of the energy storage element and the three-phase medium-voltage alternating-current bus; to complete charging of the high-voltage direct-current capacitor by boosting direct current obtained after charging of the medium-voltage direct-current capacitor through adjusting pulses of the isolated bidirectional DCDC module; and to control the input switch module to complete pre-charging of the auxiliary traction converter.

[0011] Further, the pre-charging device of the auxiliary traction converter further comprises a traction transformer and a traction motor.

[0012] The auxiliary traction converter further comprises a single-phase rectifier, a three-phase inverter, a non-isolated bidirectional DCDC module, a first switch connected with the non-isolated bidirectional DCDC module, an auxiliary inverter and a second switch connected with the auxiliary inverter.

[0013] One end of the input switch module is connected with the high-voltage direct-current capacitor via the single-phase rectifier, and the other end is connected with the traction transformer; one end of the three-phase inverter is connected with the high-voltage direct-current capacitor, and the other end is connected with the traction motor; the energy storage element is connected with the first switch; the medium-voltage direct-current capacitor is connected with the non-isolated bidirectional DCDC module and the auxiliary inverter respectively; and the second switch is connected with the three-phase medium-voltage alternating-current bus.

[0014] Further, the input switch module is composed of a main contactor and a pre-charging module in parallel; and the pre-charging module is composed of a pre-charging contactor and a pre-charging resistor in series.

[0015] In a second aspect, the application provides a pre-charging method of an auxiliary traction converter, which is implemented by using the pre-charging device of the auxiliary traction converter.

[0016] The method comprises determining to apply one of the energy storage element, the three-phase medium-voltage alternating-current bus and the input switch module to complete charging of the medium-voltage direct-current capacitor according to states of the energy storage element and the three-phase medium-voltage alternating-current bus.

[0017] The method further comprises completing charging of the high-voltage direct-current capacitor by boosting direct current obtained after charging of the medium-voltage direct-current capacitor through adjusting pulses of the isolated bidirectional DCDC module.

[0018] controlling a main contactor in the input switch module to close, completing pre-charging of the traction auxiliary converter.

[0019] Further, the determining to apply one of the energy storage element, the three-phase medium voltage AC bus and the input switch module to complete the charging of the medium voltage DC capacitor according to the states of the energy storage element and the three-phase medium voltage AC bus comprises:

[0020] when the energy storage element is available and the three-phase medium voltage AC bus is not powered, determining to apply the energy storage element to complete the charging of the medium voltage DC capacitor;

[0021] when the three-phase medium voltage AC bus is powered, determining to apply the three-phase medium voltage AC bus to complete the charging of the medium voltage DC capacitor;

[0022] when the energy storage element is not available and the three-phase medium voltage AC bus is not powered, determining to apply the input switch module to complete the charging of the medium voltage DC capacitor.

[0023] Further, the determining to apply the energy storage element to complete the charging of the medium voltage DC capacitor when the energy storage element is available and the three-phase medium voltage AC bus is not powered comprises:

[0024] when the energy storage element is available and the three-phase medium voltage AC bus is not powered, closing a first switch in the pre-charging device, the energy storage element supplying power to the medium voltage DC capacitor through a non-isolated bidirectional DCDC module in the pre-charging device.

[0025] Further, the determining to apply the three-phase medium voltage AC bus to complete the charging of the medium voltage DC capacitor when the three-phase medium voltage AC bus is powered comprises:

[0026] when the three-phase medium voltage AC bus is powered, closing a second switch in the pre-charging device, applying three-phase medium voltage AC power in the three-phase medium voltage AC bus to complete the charging of the medium voltage DC capacitor.

[0027] Further, the determining to apply one of the energy storage element, the three-phase medium voltage AC bus and the input switch module to complete the charging of the medium voltage DC capacitor according to the states of the energy storage element and the three-phase medium voltage AC bus further comprises:

[0028] obtaining an initial voltage, a terminal voltage, an instantaneous voltage, an instantaneous current and a sampling period of the medium voltage DC capacitor;

[0029] determining a capacitance value of the medium voltage DC capacitor according to the initial voltage, the terminal voltage, the instantaneous voltage, the instantaneous current and the sampling period of the medium voltage DC capacitor.

[0030] Further, the high-voltage direct-current capacitor is charged by boosting the direct current obtained after charging the medium-voltage direct-current capacitor by adjusting the pulse of the isolation bidirectional DCDC module.

[0031] The initial voltage, the terminal voltage, the instantaneous voltage, the instantaneous current and the sampling period of the high-voltage direct-current capacitor are obtained.

[0032] The capacitance of the high-voltage direct-current capacitor is determined according to the initial voltage, the terminal voltage, the instantaneous voltage, the instantaneous current and the sampling period of the high-voltage direct-current capacitor.

[0033] In a fourth aspect, the application provides a pre-charging system of a traction auxiliary converter, comprising: a train central controller and a plurality of pre-charging devices of the traction auxiliary converter.

[0034] Each pre-charging device is connected via the three-phase medium-voltage alternating-current bus.

[0035] The train central controller is connected with the controller of each pre-charging device.

[0036] The train central controller is configured to determine the pre-charging sequence of each pre-charging device according to the energy storage element state of each pre-charging device.

[0037] From the above technical solutions, the application provides a pre-charging device, system and method of a traction auxiliary converter. The device comprises a traction auxiliary converter and a three-phase medium-voltage alternating current bus. The traction auxiliary converter comprises a controller, an input switch module, an isolated bidirectional DCDC module, an energy storage element, a high-voltage direct current capacitor and a medium-voltage direct current capacitor. The controller is connected with the input switch module and the isolated bidirectional DCDC module respectively. The isolated bidirectional DCDC module is connected with the high-voltage direct current capacitor, the medium-voltage direct current capacitor and the energy storage element respectively. The input switch module is connected with the high-voltage direct current capacitor. The three-phase medium-voltage alternating current bus is connected with the medium-voltage direct current capacitor. The controller is used to determine to complete the charging of the medium-voltage direct current capacitor by using one of the energy storage element, the three-phase medium-voltage alternating current bus and the input switch module according to the states of the energy storage element and the three-phase medium-voltage alternating current bus. The direct current obtained after the charging of the medium-voltage direct current capacitor is boosted by adjusting the pulse of the isolated bidirectional DCDC module, so as to complete the charging of the high-voltage direct current capacitor. The pre-charging of the traction auxiliary converter is completed by controlling the input switch module, which can reduce the current impact and action frequency of the switch element in the input switch module, help to improve the element life and reduce the failure rate, and further improve the reliability of the pre-charging of the traction converter. Specifically, the availability of the converter can be significantly improved. When the pre-charging resistance heat is limited, the converter can still use other methods for pre-charging. The capacitance estimation of the internal capacitor of the converter can be completed in the pre-charging process, which can be used for the life prediction of the direct current capacitor component of the converter, the internal self-checking of the converter and other work. BRIEF DESCRIPTION OF DRAWINGS

[0038] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings needed to be used in the embodiments or the prior art 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 labor.

[0039] Figure 1 is a structure schematic diagram of the pre-charging device of the traction auxiliary converter in the embodiments of the present application;

[0040] Figure 2 is a structure schematic diagram of the isolated bidirectional DCDC module in an example of the present application;

[0041] Figure 3 is a structure schematic diagram of the non-isolated bidirectional DCDC module in an example of the present application;

[0042] Figure 4 is a structure schematic diagram of the auxiliary inverter in an example of the present application;

[0043] Figure 5 is a structural schematic diagram of an input switch module in an embodiment of the present application;

[0044] Figure 6 is a flowchart of a pre-charging method of a traction auxiliary converter in an embodiment of the present application;

[0045] Figure 7 is a flowchart of steps 110 to 130 of a pre-charging method of a traction auxiliary converter in an embodiment of the present application;

[0046] Figure 8 is a flowchart of a pre-charging method of a traction auxiliary converter in an application example of the present application;

[0047] Figure 9 is a flowchart of a train-level pre-charging method of a traction auxiliary converter in an application example of the present application;

[0048] Figure 10 is a structural schematic diagram of a pre-charging system of a traction auxiliary converter in an embodiment of the present application. DETAILED DESCRIPTION

[0049] In order to enable persons skilled in the art to better understand the technical solutions in the present specification, the technical solutions in the embodiments of the present application will be described clearly and completely below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only some of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by persons skilled in the art without creative labor fall within the scope of protection of the present application.

[0050] The pre-charging device, system and method of the traction auxiliary converter disclosed in the present application can be used in the field of vehicle-mounted energy storage, and can also be used in any field other than the field of vehicle-mounted energy storage. The application field of the pre-charging device, system and method of the traction auxiliary converter disclosed in the present application is not limited.

[0051] The embodiments are specifically described as follows.

[0052] In order to reduce the current impact and action frequency of the switching elements in the input switch module, improve the element life and reduce the failure rate, and further improve the reliability of the pre-charging of the traction converter, the present application provides an embodiment of a pre-charging device of a traction auxiliary converter, as shown in Figure 1As shown, specifically contains: traction auxiliary converter and three-phase medium voltage AC bus; the traction auxiliary converter includes: controller, input switch module, isolated bidirectional DCDC module, energy storage element, high voltage DC capacitor and medium voltage DC capacitor; the controller is connected with the input switch module and isolated bidirectional DCDC module respectively; the isolated bidirectional DCDC module is connected with the high voltage DC capacitor, medium voltage DC capacitor and energy storage element respectively; the input switch module is connected with the high voltage DC capacitor; the three-phase medium voltage AC bus is connected with the medium voltage DC capacitor;Wherein, the controller is used to determine to apply one of the energy storage element, three-phase medium voltage AC bus and input switch module to complete the charging of the medium voltage DC capacitor according to the state of the energy storage element and three-phase medium voltage AC bus;By adjusting the pulse of the isolated bidirectional DCDC module, the DC power obtained after charging the medium voltage DC capacitor is boosted to complete the charging of the high voltage DC capacitor;And control the input switch module to complete the pre-charging of the traction auxiliary converter.

[0053] Specifically, the energy storage element includes but is not limited to battery, and the energy storage element can be composed of battery, fuse, battery management system and the like;The input switch module is connected with the secondary winding of the traction transformer on one side and connected with the AC input end of the single-phase rectifier on the other side;The isolated bidirectional DCDC module is connected with the high voltage DC capacitor on one side and connected with the medium voltage DC capacitor on the other side.

[0054] In an example, as shown in Figure 2 Port 1 of the isolated bidirectional DCDC module is connected with the high voltage DC capacitor, and port 2 is connected with the medium voltage DC capacitor. The controller realizes the voltage stabilization control of the medium voltage DC bus by adjusting the pulse width, phase shift angle or switching frequency of the isolated bidirectional DCDC module, thereby supplying power to the AC and DC loads on the vehicle. The specific implementation form of the isolated bidirectional DCDC module can be but is not limited to bidirectional active bridge converter, Q1, Q2 form bridge arm 1 in series, Q3, Q4 form bridge arm 2 in series, Q5, Q6 form bridge arm 3 in series, Q7, Q8 form bridge arm 4 in series, bridge arm 1, 2 are connected in parallel with the high voltage DC capacitor, the midpoint of bridge arm 1 is connected with one end of inductor L1, the other end of inductor L1 and the midpoint of bridge arm 2 are connected with the primary winding of medium frequency transformer M respectively, and the midpoint of bridge arm 2 is connected with the other end of the primary winding of medium frequency transformer M;Bridge arm 3, 4 are connected in parallel with the medium voltage DC capacitor, and the midpoints of bridge arm 3, 4 are connected with the secondary winding of medium frequency transformer M.

[0055] As shown in Figure 1As shown in one embodiment of the present application, the pre-charging device of the traction auxiliary converter further comprises a traction transformer and a traction motor; the traction auxiliary converter further comprises a single-phase rectifier, a three-phase inverter, a non-isolated bidirectional DC / DC module, a first switch connected to the non-isolated bidirectional DC / DC module, an auxiliary inverter, and a second switch connected to the auxiliary inverter; one end of the input switch module is connected to the high-voltage direct-current capacitor via the single-phase rectifier, and the other end is connected to the traction transformer; one end of the three-phase inverter is connected to the high-voltage direct-current capacitor, and the other end is connected to the traction motor; the energy storage element is connected to the first switch; the medium-voltage direct-current capacitor is connected to the non-isolated bidirectional DC / DC module and the auxiliary inverter respectively; and the second switch is connected to the three-phase medium-voltage alternating-current bus.

[0056] Specifically, the first switch is a switching component connected between the non-isolated bidirectional DC / DC module and the energy storage element; one side of the non-isolated bidirectional DC / DC module is connected to the medium-voltage direct-current capacitor, and the other side is connected to the energy storage element via the first switch. The non-isolated bidirectional DC / DC module is composed of a switching tube, an inductor, and a capacitor. Here, a Buck-Boost circuit can be used, but is not limited to it. The controller adjusts the switching tube pulse to realize controllable charging and discharging current of the energy storage element; the auxiliary inverter can be a three-phase inverter power module, which converts the direct current of the medium-voltage direct-current capacitor into pulse width modulated three-phase alternating current, and then connects to the three-phase medium-voltage alternating-current bus of the train via the second switch. The controller detects the output voltage and current value of the three-phase inverter power module, and then adjusts the switching tube pulse to realize controllable voltage and current of the auxiliary inverter.

[0057] In one example, as shown in Figure 3 , the non-isolated bidirectional DC / DC module is composed of a switching tube, an inductor, and a capacitor. Here, a modified Boost circuit can be used, but is not limited to it. Figure 4 , the port 1 of the auxiliary inverter is connected to the medium-voltage direct-current bus, and the port 2 is connected to the three-phase medium-voltage alternating-current bus via the second switch. 11 , Q 12 are connected in series to form an A-phase bridge arm, 13 , Q 14 are connected in series to form a B-phase bridge arm, 15 , Q 16 are connected in series to form a C-phase bridge arm, and the inductor L a , L b , and L c are three-phase filter inductors, and C a , C b , and C c are three-phase filter capacitors. The controller detects the voltage and current value of the input and output ports of the three-phase inverter power module, and then adjusts the switching tube pulse to realize voltage and current regulation and bidirectional energy conversion of the auxiliary inverter.

[0058] As Figure 5 shown in one embodiment of the present application, the input switch module is composed of a main contactor and a pre-charging module in parallel; the pre-charging module is composed of a pre-charging contactor and a pre-charging resistor in series.

[0059] Specifically, the input switch module is composed of a pre-charging contactor and a pre-charging resistor in series, and is connected in parallel with the main contactor; the controller can control the closing and opening of the pre-charging contactor and the main contactor.

[0060] To further illustrate the present scheme, the present application provides an application example of a traction auxiliary converter pre-charging device, which is described in detail as follows:

[0061] In the application example, the traction auxiliary converter pre-charging device (i.e., the traction auxiliary converter pre-charging architecture) is composed of an input switch module, an isolated bidirectional DCDC module, a non-isolated bidirectional DCDC module, a switch module, an energy storage element (the energy storage element includes but is not limited to a battery), a single-phase rectifier, an auxiliary inverter, and a controller.

[0062] The input switch module is composed of a main contactor and a pre-charging module in parallel, and the pre-charging module is composed of a pre-charging contactor and a pre-charging resistor in series. The controller controls the closing and opening of the pre-charging contactor and the main contactor. One side of the input switch module is connected to the secondary winding of the traction transformer, and the other side is connected to the AC input end of the single-phase rectifier.

[0063] On the basis of the above scheme, the isolated bidirectional DCDC module can also use other DCDC converters with bidirectional isolation characteristics, such as LLC, CLLC converters, etc. The full-bridge on both sides of the intermediate-frequency transformer can be two-level half-bridge, three-level half-bridge, etc. To obtain higher power level, the bridge arms can also be in series or cascade form.

[0064] The energy storage element is composed of a battery, a fuse, a battery management system, etc. The first switch is a switching component connecting the non-isolated bidirectional DCDC module and the energy storage element, and the first switch receives the instructions of the controller to realize the on and off functions.

[0065] One side of the non-isolated bidirectional DCDC module is connected to the medium-voltage DC capacitor, and the other side is connected to the energy storage element through the first switch. The controller adjusts the switching tube pulse to realize the controllable charging and discharging current of the energy storage element.

[0066] The auxiliary inverter is a three-phase inverter power module, which converts the direct current of the medium-voltage DC bus into pulse width modulated three-phase alternating current, and then accesses the three-phase medium-voltage AC bus of the train through the second switch. The voltage system includes but is not limited to 380V / 50Hz, 440V / 60Hz. The inverter can also work in a rectification mode to convert the alternating current of the three-phase medium-voltage AC bus into medium-voltage direct current.

[0067] The train connects the three-phase medium-voltage AC buses of all traction auxiliary converters together through contactors, and the central controller of the train directly controls the closing and opening of the contactors.

[0068] The control of the pre-charging architecture of the traction auxiliary converter is divided into single traction auxiliary converter pre-charging control and train-level pre-charging control.

[0069] In order to reduce the current impact and action frequency of the switching elements in the input switching module, improve the element life and reduce the failure rate, and thus improve the reliability of the pre-charging of the traction converter, the embodiment provides a pre-charging method of a traction auxiliary converter, which is executed by a controller, and is implemented by using a pre-charging device of the traction auxiliary converter, as shown in Figure 6 The method specifically includes the following contents:

[0070] Step 100: According to the state of the energy storage element and the three-phase medium-voltage AC bus, determine to complete the charging of the medium-voltage DC capacitor by using one of the energy storage element, the three-phase medium-voltage AC bus and the input switching module.

[0071] Specifically, the medium-voltage DC capacitor charging can be further divided into two modes according to whether the energy storage element is connected. When the energy storage element is available and the medium-voltage AC bus has no power, mode one is adopted; when the medium-voltage AC bus has power, mode two is adopted; when the energy storage element is not available and the medium-voltage AC bus has no power, the traditional input switching module is used for pre-charging. Traditionally, the traction auxiliary converter usually uses the input switching module for pre-charging.

[0072] Mode one: The energy storage element is used for pre-charging. The first switch connected to the energy storage element is closed, and the energy storage element supplies power to the medium-voltage DC capacitor through the non-isolated bidirectional DCDC module. The non-isolated bidirectional DCDC module can work in a controlled mode, in which the voltage of the medium-voltage DC capacitor is a controllable direct current with an amplitude higher than that of the energy storage element. The non-isolated bidirectional DCDC module can also work in an uncontrolled mode, in which the switch tube is not in action and the diode element is in conduction, so that the voltage of the medium-voltage DC capacitor is equal to the voltage of the energy storage element. During the charging process, the charging instantaneous power curve of the medium-voltage DC capacitor is calculated by detecting the discharge current and voltage of the energy storage element, and the voltage rising curve of the medium-voltage DC capacitor is detected, so as to calculate the capacitance value of the medium-voltage DC capacitor.

[0073] Mode two: using the energy of three-phase medium-voltage AC bus to pre-charge. Close the second switch, use the output of other traction auxiliary inverter to output three-phase medium-voltage AC power, complete the charging of medium-voltage DC capacitor. Through detecting the voltage of three-phase medium-voltage AC bus and the current of input auxiliary inverter, calculate the charging instantaneous power curve of medium-voltage DC capacitor, and detect the voltage rising curve of medium-voltage DC capacitor, so as to calculate the capacitance of medium-voltage DC capacitor.

[0074] Step 200: boost the DC power obtained after charging the medium-voltage DC capacitor by adjusting the pulse of the isolated bidirectional DCDC module, to complete the charging of the high-voltage DC capacitor.

[0075] Specifically, the controller can control the isolated bidirectional DCDC module to charge the high-voltage DC capacitor by boosting the DC power of the medium-voltage DC capacitor. During the charging process, the voltage of the high-voltage DC capacitor is detected in real time. If the voltage reaches the pre-charging set value within a limited time, such as the rated DC bus voltage of the inverter, the pre-charging is ended. The isolated bidirectional DCDC module stops working. If the voltage cannot reach the pre-charging set value within a limited time, the pre-charging is ended, and the pre-charging process is continued for several times. If the pre-charging set value still cannot be reached, the traction auxiliary inverter is blocked. In the above process, the charging instantaneous power curve of the high-voltage DC capacitor is calculated through detecting the discharge current and voltage of the isolated bidirectional DCDC module, and the capacitance of the medium-voltage DC capacitor is calculated in combination with the voltage rising curve of the medium-voltage DC capacitor.

[0076] Step 300: control the main contactor in the input switch module to be closed, to complete the pre-charging of the traction auxiliary inverter.

[0077] Specifically, the controller can control the main contactor in the input switch module to be closed, to complete all pre-charging processes. After that, the single-phase rectifier can start working or work in a non-controlled rectification state. The single-phase rectifier converts the AC power input by the traction auxiliary inverter into DC power on the high-voltage DC capacitor. The isolated bidirectional DCDC module starts working to convert the electric energy on the high-voltage DC capacitor into DC power on the medium-voltage DC capacitor. The non-isolated bidirectional DCDC module can start charging and discharging the energy storage element. The auxiliary inverter starts working, the second switch is closed, and the three-phase medium-voltage AC bus of the train is powered to provide AC power for the load on the bus.

[0078] In order to further improve the flexibility of pre-charging of the traction auxiliary inverter, and further improve the reliability of the inverter, referring to Figure 7 In an embodiment of the present application, step 100 includes:

[0079] Step 110: when the energy storage element is available and the three-phase medium-voltage AC bus is not powered, determining to apply the energy storage element to complete the charging of the medium-voltage DC capacitor;

[0080] Step 120: when the three-phase medium-voltage AC bus is powered, determining to apply the three-phase medium-voltage AC bus to complete the charging of the medium-voltage DC capacitor;

[0081] Step 130: when the energy storage element is not available and the three-phase medium-voltage AC bus is not powered, determining to apply the input switch module to complete the charging of the medium-voltage DC capacitor.

[0082] In order to further improve the reliability of the energy storage element power supply, in an embodiment of the present application, step 110 comprises:

[0083] Step 111: when the energy storage element is available and the three-phase medium-voltage AC bus is not powered, closing a first switch in the pre-charging device, and the energy storage element supplies power to the medium-voltage DC capacitor through a non-isolated bidirectional DC / DC module in the pre-charging device.

[0084] In order to further improve the reliability of the three-phase medium-voltage AC bus power supply, in an embodiment of the present application, step 120 comprises:

[0085] Step 121: when the three-phase medium-voltage AC bus is powered, closing a second switch in the pre-charging device, and applying three-phase medium-voltage AC power in the three-phase medium-voltage AC bus to complete the charging of the medium-voltage DC capacitor.

[0086] In order to improve the reliability of the traction auxiliary converter to achieve pre-charging, and to achieve the capacity estimation of the capacitor, and further to achieve the prediction of the life of the capacitor component, in an embodiment of the present application, step 110 further comprises:

[0087] Obtaining the initial voltage, the terminal voltage, the instantaneous voltage, the instantaneous current and the sampling period of the medium-voltage DC capacitor; and determining the capacity of the medium-voltage DC capacitor according to the initial voltage, the terminal voltage, the instantaneous voltage, the instantaneous current and the sampling period of the medium-voltage DC capacitor.

[0088] Specifically, the initial voltage of the medium-voltage DC capacitor can represent the voltage when the medium-voltage DC capacitor starts charging, and the terminal voltage can represent the voltage when the medium-voltage DC capacitor finishes charging; and the capacity of the medium-voltage DC capacitor can be calculated according to the following formula:

[0089]

[0090] Wherein, C M is the capacity of the medium-voltage DC capacitor, U1 and U2 are the initial voltage and the terminal voltage of the medium-voltage DC capacitor respectively, and u iand i i are the instantaneous voltage and current of the medium-voltage DC bus, respectively, T s is the sampling period.

[0091] To improve the reliability of the pre-charge of the traction auxiliary converter and realize the estimation of the capacitance value of the capacitor, and further realize the prediction of the service life of the capacitor component, in an embodiment of the present application, step 120 further includes:

[0092] The initial voltage, the terminal voltage, the instantaneous voltage, the instantaneous current, and the sampling period of the high-voltage DC capacitor are obtained; and the capacitance value of the high-voltage DC capacitor is determined according to the initial voltage, the terminal voltage, the instantaneous voltage, the instantaneous current, and the sampling period of the high-voltage DC capacitor.

[0093] Specifically, the initial voltage of the high-voltage DC capacitor can represent the voltage when the high-voltage DC capacitor starts to charge, and the terminal voltage can represent the voltage when the high-voltage DC capacitor finishes charging; and the capacitance value of the high-voltage DC capacitor can be calculated according to the following formula:

[0094]

[0095] wherein C H is the capacitance value of the high-voltage DC capacitor, U3 and U4 are the initial voltage and the terminal voltage of the high-voltage DC capacitor, respectively, u j and i j are the instantaneous voltage and the instantaneous current flowing into the high-voltage DC capacitor, respectively, T s is the sampling period.

[0096] Traditionally, the traction auxiliary converter uses an input switch module for pre-charge, as shown in Figure 8 The present application proposes a new pre-charge control method different from the traditional scheme, and the application example is described as follows:

[0097] Step 1: complete the charging of the medium-voltage DC capacitor. According to whether the energy storage element is connected, it can be further divided into two modes. When the energy storage element is available and the three-phase medium-voltage AC bus has no power, mode one can be used; when the three-phase medium-voltage AC bus has power, mode two can be used; when the energy storage element is not available and the three-phase medium-voltage AC bus has no power, the traditional input switch module is used for pre-charge.

[0098] Mode one: using energy storage element for pre-charging. Close the first switch connected with energy storage element, energy storage element supplies power to medium voltage DC capacitor through non-isolated bidirectional DCDC module. Non-isolated bidirectional DCDC module can work in controlled mode, at this time the voltage of medium voltage DC capacitor is controllable DC higher than the amplitude of energy storage element voltage. Non-isolated bidirectional DCDC module can also work in uncontrolled mode, at this time its switch tube does not act, diode element is turned on, so that the voltage of medium voltage DC capacitor is equal to the voltage of energy storage element. During the charging process, by detecting the discharge current and voltage of energy storage element, the instantaneous power curve of medium voltage DC capacitor is calculated, and the voltage rising curve of medium voltage DC capacitor is detected, so as to calculate the capacitance value of medium voltage DC capacitor. The specific calculation formula is:

[0099]

[0100] Wherein, C M is the capacitance value of medium voltage DC capacitor, U1 and U2 are the initial voltage and terminal voltage of medium voltage DC capacitor respectively, u i and i i are the instantaneous voltage and current of medium voltage DC bus respectively, T s is the sampling period.

[0101] Mode two: using the energy of three-phase medium voltage AC bus for pre-charging. Close the second switch, use the output three-phase medium voltage AC of other traction auxiliary converter to complete the charging of medium voltage DC capacitor. By detecting the voltage of three-phase medium voltage AC bus and the current of input auxiliary inverter, the instantaneous power curve of medium voltage DC capacitor is calculated, and the voltage rising curve of medium voltage DC capacitor is detected, so as to calculate the capacitance value of medium voltage DC capacitor. The specific calculation formula is:

[0102]

[0103] Wherein, C M is the capacitance value of medium voltage DC capacitor, U1 and U2 are the initial voltage and terminal voltage of medium voltage DC capacitor respectively, u i and i i are the instantaneous voltage and current of medium voltage DC bus respectively, T s is the sampling period.

[0104] Step 2: High-voltage DC capacitor charging is performed. The controller charges the high-voltage DC capacitor by regulating the pulse of the isolated bidirectional DC / DC module to step up the DC voltage of the medium-voltage DC capacitor. During the charging process, the voltage of the high-voltage DC capacitor is detected in real time. If the voltage reaches the pre-charging set value within a limited time, such as the rated DC bus voltage of the converter, the pre-charging process is ended. The isolated bidirectional DC / DC module stops working. If the voltage cannot reach the pre-charging set value within a limited time, the pre-charging process is ended, and the pre-charging process is continued for several times. If the pre-charging set value cannot be reached, the traction auxiliary converter is locked. During the above process, the charging instantaneous power curve of the high-voltage DC capacitor is calculated by detecting the discharge current and voltage of the isolated bidirectional DC / DC module, and the capacitance of the medium-voltage DC capacitor is calculated in combination with the voltage rising curve of the medium-voltage DC capacitor. The calculation formula is as follows:

[0105]

[0106] wherein C H is the capacitance of the high-voltage DC capacitor, U3 and U4 are the initial voltage and the terminal voltage of the high-voltage DC capacitor respectively, u j and i j are the instantaneous voltage across the high-voltage DC capacitor and the instantaneous current flowing into the high-voltage DC capacitor respectively, and T s is the sampling period.

[0107] Step 3: The main contactor is closed, and the traction auxiliary converter is started. The controller controls the main contactor in the input switch module to be closed to complete all pre-charging processes. Then the single-phase rectifier can be started to work or work in a non-controlled 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. The isolated bidirectional DC / DC module starts to work to convert the power on the high-voltage DC capacitor into DC power on the medium-voltage DC capacitor. The non-isolated bidirectional DC / DC module can start to charge and discharge the energy storage element. The auxiliary inverter starts to work, the second switch is closed, and AC power is supplied to the three-phase medium-voltage AC bus of the train to provide AC power for the load on the bus.

[0108] Further, referring to Figure 9 , the train-level pre-charging control process includes: detecting whether the energy storage element has available power, and if so, selecting any traction auxiliary converter with available energy storage element to send a pre-charging instruction, or selecting any traction auxiliary converter to send a pre-charging instruction; closing the medium-voltage AC bus contactor and sending a second switch closing instruction; detecting whether the three-phase medium-voltage AC bus has power, and if so, sending a pre-charging instruction to other traction auxiliary converters; and the specific description is as follows:

[0109] Step 11: The train central control unit detects the state of the train energy storage element, and selects the first pre-charging traction converter unit. If the train has available energy storage elements, then among all the traction auxiliary converters with available energy storage elements, one is selected to start pre-charging. If all the energy storage elements of the traction auxiliary converters on the train are not available, then one is selected to start pre-charging.

[0110] Step 12: If the controller of the traction auxiliary converter receives the instruction to start pre-charging, it executes according to the pre-charging control strategy of the single traction auxiliary converter described above.

[0111] Step 13: The train central control unit controls the closing of the contactors between the three-phase medium-voltage AC bus, and sends an instruction to close the second switch to all traction auxiliary converters.

[0112] Step 14: After detecting that the three-phase medium-voltage AC bus is powered, the train central control unit sends a pre-charging instruction to all the remaining traction auxiliary converters.

[0113] In order to reduce the current impact and action frequency of the switching elements in the input switch module, improve the element life and reduce the failure rate, and thus improve the reliability of the pre-charging of the traction converter, as shown in Figure 10 The pre-charging system of the traction auxiliary converter provided in the embodiment of the application comprises: a train central controller and a plurality of pre-charging devices of the traction auxiliary converter; each pre-charging device is connected via the three-phase medium-voltage AC bus; the controller of each pre-charging device is connected to the train central controller; and the train central controller is used to determine the pre-charging sequence of each pre-charging device according to the state of the energy storage element of each pre-charging device.

[0114] Specifically, any one traction auxiliary converter can complete pre-charging first, and mode one can be used, or a traditional pre-charging method, i.e., the input switch module completes pre-charging. Then, the remaining traction auxiliary converters can use mode two for pre-charging. Specifically, it can be divided into four steps:

[0115] Step one, after the train central control unit is powered on, it detects the state of the train energy storage element, and selects the first pre-charging traction converter unit. If the train has available energy storage elements, then among all the traction auxiliary converters with available energy storage elements, one is selected to start pre-charging. If all the energy storage elements of the traction auxiliary converters on the train are not available, then one is selected to start pre-charging.

[0116] Step two, if the controller of the traction auxiliary converter receives the instruction to start pre-charging, it executes according to the pre-charging control strategy of the single traction auxiliary converter described above.

[0117] Step three, the central control unit of the train controls the contactor between the medium voltage AC bus to close, and sends the instruction of closing the second switch to all traction auxiliary converters.

[0118] Step four, the central control unit of the train commands all the remaining traction auxiliary converters to pre-charge after detecting that one traction auxiliary converter completes pre-charge and the auxiliary inverter completes medium voltage AC output, and pre-charge the traction auxiliary converter by mode two preferentially.

[0119] From the above description, the pre-charge device, system and method of the traction auxiliary converter provided by the application can implement the architecture and control method of pre-charging the traction auxiliary converter of the locomotive vehicle by using the on-board energy storage, and has the function of recognizing the health degree of the capacitor; the current impact and action frequency of the switching element in the input switch module can be reduced, which helps to improve the service life of the element and reduce the failure rate, thereby improving the reliability of the pre-charge of the traction converter; specifically, the availability of the converter can be significantly improved, and when the heat of the pre-charge resistor is limited, the converter can still be pre-charged by other methods; during the pre-charge process, the capacitance estimation of the internal capacitor of the converter can be completed, which can be used for life prediction of the DC capacitor component of the converter, internal self-checking of the converter and the like.

[0120] The embodiments of the above method in the application are described in a progressive manner, and the same and similar parts between the embodiments can be referred to each other. Each embodiment mainly explains the difference from other embodiments. The related parts can be referred to the part of the method embodiment.

[0121] Those skilled in the art should understand that the embodiments of the application can be provided as a method, a system or a computer program product. Therefore, the application can be in the form of a complete hardware embodiment, a complete software embodiment or an embodiment combining software and hardware aspects. Moreover, the application can be in the form of a computer program product implemented on one or more computer usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer usable program code.

[0122] The application is described with reference to the flowcharts and / or block diagrams according to the method, equipment (system) and computer program product of the embodiments of the application. It should be understood that each flow and / or block in the flowcharts and / or block diagrams, and the combination of the flows and / or blocks in the flowcharts and / or block diagrams can be implemented by computer program instructions. These computer program instructions can be provided to the processor of a general-purpose computer, a special-purpose computer, an embedded processor or other programmable data processing equipment to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing equipment produce the functions described in the flowcharts and / or block diagrams. Figure 1 one flow or multiple flows and / or blocksFigure 1 A device that provides the functions specified in one or more boxes.

[0123] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Figure 1 One or more processes and / or boxes Figure 1 The function specified in one or more boxes.

[0124] These computer program instructions may also be loaded onto a computer or other programmable data processing equipment to cause a series of operational steps to be performed on the computer or other programmable equipment to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable equipment for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 The steps of the function specified in one or more boxes.

[0125] This application uses specific embodiments to illustrate the principles and implementation methods of this application. The description of the above embodiments is only for the purpose of helping to understand the method and core ideas of this application. At the same time, for those skilled in the art, there will be changes in the specific implementation methods and application scope based on the ideas of this application. Therefore, the content of this specification should not be construed as a limitation of this application.

Claims

1. A pre-charging device for a traction auxiliary converter, characterized in that, include: Traction auxiliary converter and three-phase medium-voltage AC bus; The traction auxiliary converter includes: a controller, an input switch module, an isolated bidirectional DC-DC module, an energy storage element, a high-voltage DC capacitor, and a medium-voltage DC capacitor; The controller is connected to the input switch module and the isolated bidirectional DC-DC converter module respectively; the isolated bidirectional DC-DC converter module is connected to the high-voltage DC capacitor, the medium-voltage DC capacitor, and the energy storage element respectively; the input switch module is connected to the high-voltage DC capacitor; the three-phase medium-voltage AC bus is connected to the medium-voltage DC capacitor; and the isolated bidirectional DC-DC converter module is a DC-DC converter with bidirectional isolation characteristics. The controller is configured to determine, based on the state of the energy storage element and the three-phase medium-voltage AC bus, to use one of the following to charge the medium-voltage DC capacitor: the energy storage element, the three-phase medium-voltage AC bus, and the input switch module; to boost the DC voltage obtained after charging the medium-voltage DC capacitor by adjusting the pulse of the isolated bidirectional DC-DC module, thereby charging the high-voltage DC capacitor; and to control the input switch module to pre-charge the traction auxiliary converter. The step of determining, based on the state of the energy storage element and the three-phase medium-voltage AC bus, to use one of the energy storage element, the three-phase medium-voltage AC bus, and the input switch module to complete the charging of the medium-voltage DC capacitor includes: When the energy storage element is available and the three-phase medium-voltage AC bus is de-energized, the energy storage element is used to charge the medium-voltage DC capacitor. When the three-phase medium-voltage AC bus is energized, the second switch in the pre-charging device is closed, and other traction auxiliary converters are used to output three-phase medium-voltage AC power to charge the medium-voltage DC capacitor. When the energy storage element is unavailable and the three-phase medium-voltage AC bus is de-energized, the input switch module is used to charge the medium-voltage DC capacitor.

2. The pre-charging device for the traction auxiliary converter according to claim 1, characterized in that, Also includes: Traction transformer and traction motor; The traction auxiliary converter also includes: a single-phase rectifier, a three-phase inverter, a non-isolated bidirectional DC-DC module, a first switch connected to the non-isolated bidirectional DC-DC module, an auxiliary inverter, and a second switch connected to the auxiliary inverter. One end of the input switch module is connected to the high-voltage DC capacitor via the single-phase rectifier, and the other end is connected to the traction transformer; one end of the three-phase inverter is connected to the high-voltage DC capacitor, and the other end is connected to the traction motor; the energy storage element is connected to the first switch; the medium-voltage DC capacitor is connected to the non-isolated bidirectional DC-DC module and the auxiliary inverter respectively; the second switch is connected to the three-phase medium-voltage AC bus.

3. The pre-charging device for the traction auxiliary converter according to claim 1, characterized in that, The input switch module consists of a main contactor and a pre-charge module connected in parallel; the pre-charge module consists of a pre-charge contactor and a pre-charge resistor connected in series.

4. A pre-charging method for a traction auxiliary converter, characterized in that, The method is implemented using a pre-charging device for the traction auxiliary converter as described in any one of claims 1 to 3, the method comprising: Based on the state of the energy storage element and the three-phase medium-voltage AC bus, determine which of the following should be used to charge the medium-voltage DC capacitor: the energy storage element, the three-phase medium-voltage AC bus, and the input switch module. By adjusting the pulse of the isolated bidirectional DC-DC module, the DC current obtained after charging the medium-voltage DC capacitor is boosted to complete the charging of the high-voltage DC capacitor. The main contactor in the input switch module is closed to complete the pre-charging of the traction auxiliary converter.

5. The pre-charging method for the traction auxiliary converter according to claim 4, characterized in that, The step of determining, based on the state of the energy storage element and the three-phase medium-voltage AC bus, to use one of the energy storage element, the three-phase medium-voltage AC bus, and the input switch module to complete the charging of the medium-voltage DC capacitor includes: When the energy storage element is available and the three-phase medium-voltage AC bus is de-energized, it is determined that the energy storage element will be used to charge the medium-voltage DC capacitor. When the three-phase medium-voltage AC bus is energized, it is determined that the three-phase medium-voltage AC bus will be used to charge the medium-voltage DC capacitor. When the energy storage element is unavailable and the three-phase medium-voltage AC bus is de-energized, the input switch module is used to charge the medium-voltage DC capacitor.

6. The pre-charging method for the traction auxiliary converter according to claim 5, characterized in that, The step of determining to use the energy storage element to charge the medium-voltage DC capacitor when the energy storage element is available and the three-phase medium-voltage AC bus is de-energized includes: When the energy storage element is available and the three-phase medium-voltage AC bus is de-energized, the first switch in the pre-charging device is closed, and the energy storage element supplies power to the medium-voltage DC capacitor through the non-isolated bidirectional DC-DC module in the pre-charging device.

7. The pre-charging method for the traction auxiliary converter according to claim 5, characterized in that, When the three-phase medium-voltage AC bus is energized, determining to use the three-phase medium-voltage AC bus to charge the medium-voltage DC capacitor includes: When the three-phase medium-voltage AC bus is energized, the second switch in the pre-charging device is closed, and the three-phase medium-voltage AC power in the three-phase medium-voltage AC bus is used to charge the medium-voltage DC capacitor.

8. The pre-charging method for the traction auxiliary converter according to claim 4, characterized in that, The step of determining, based on the state of the energy storage element and the three-phase medium-voltage AC bus, to use one of the energy storage element, the three-phase medium-voltage AC bus, and the input switch module to complete the charging of the medium-voltage DC capacitor further includes: Obtain the initial voltage, termination voltage, instantaneous voltage, instantaneous current, and sampling period of the medium-voltage DC capacitor; The capacitance value of the medium-voltage DC capacitor is determined based on its initial voltage, termination voltage, instantaneous voltage, instantaneous current, and sampling period.

9. The pre-charging method for the traction auxiliary converter according to claim 4, characterized in that, The step of boosting the DC voltage obtained after charging the medium-voltage DC capacitor by adjusting the pulse of the isolated bidirectional DC-DC module to complete the charging of the high-voltage DC capacitor also includes: The initial voltage, termination voltage, instantaneous voltage, instantaneous current, and sampling period of the high-voltage DC capacitor are obtained. The capacitance value of the high-voltage DC capacitor is determined based on its initial voltage, termination voltage, instantaneous voltage, instantaneous current, and sampling period.

10. A pre-charging system for a traction auxiliary converter, characterized in that, include: The train central controller and a pre-charging device for a plurality of traction auxiliary converters as described in any one of claims 1 to 3; The various pre-charging devices are connected via the three-phase medium-voltage AC bus; The train central controller is connected to the controller of each pre-charging device; The train central controller is used to determine the pre-charging sequence of each pre-charging device based on the state of the energy storage elements of each pre-charging device.

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