CN114421789A - Pre-charging device, system and method for traction auxiliary converter - Google Patents

Abstract

The application provides a pre-charging device, a system and a method of a traction auxiliary converter, wherein the device comprises: a traction auxiliary converter and a three-phase medium-voltage alternating-current bus; the traction-assist converter includes: the device comprises a controller, an input switch module, an isolation bidirectional DCDC module, an energy storage element, a high-voltage direct current capacitor and a medium-voltage direct current capacitor; the controller is respectively connected with the input switch module and the isolated bidirectional DCDC module; the isolation bidirectional DCDC module is respectively connected with the high-voltage direct-current capacitor, the medium-voltage direct-current capacitor and the energy storage element; 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 method and the device can reduce the current impact and the action frequency of the switching element in the input switch module, are beneficial to prolonging the service life of the element and reducing the failure rate, and further can improve the reliability of the pre-charging of the traction converter.

Description

Precharging device, system and method for traction auxiliary converter

technical field

The present application relates to the technical field of on-board energy storage, and in particular, to a precharging device, system and method for a traction auxiliary converter.

Background technique

At present, the traction converter of high-speed EMU generally adopts the AC-DC-AC circuit structure of four-quadrant rectifier and 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 through the uncontrolled rectifier, which will cause a large instantaneous inrush current, thus affecting the equipment. safety and longevity.

Therefore, it is necessary to adopt a pre-charging method to energize the traction converter under the condition of limited inrush current; usually, a pre-charging unit is installed on the AC input side of the traction converter, and the pre-charging unit can be connected by the pre-charging contactor and The pre-charging resistors are connected in series and connected in parallel with the main contactor. When the traction converter starts, the pre-charging contactor is first closed, and the AC input voltage charges the DC link capacitor through the pre-charging resistor to suppress the starting current. After the DC voltage rises to a higher level, the main contactor is closed. , that is, the start-up process of the entire pre-charge is completed.

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

SUMMARY OF THE INVENTION

In view of at least one problem in the prior art, the present application proposes a precharging device, system and method for a traction auxiliary converter, which can reduce the current impact and operating frequency of switching elements in the input switch module, and help improve the components life and reduce failure rates, which in turn can improve the reliability of traction converter pre-charging.

In order to solve the above-mentioned technical problems, the application provides the following technical solutions:

In a first aspect, the present application provides a precharging device for a traction auxiliary converter, including: a traction auxiliary converter and a three-phase medium-voltage AC bus;

The traction auxiliary converter includes: a controller, an input switch module, an isolated bidirectional DCDC module, an energy storage element, a high-voltage DC capacitor and a medium-voltage DC capacitor;

The controller is respectively connected with the input switch module and the isolated bidirectional DCDC module; the isolated bidirectional DCDC module is respectively connected with the high voltage DC capacitor, the medium voltage DC capacitor and the energy storage element; the input switch module is connected with the The high-voltage DC capacitor is connected; the three-phase medium-voltage AC bus is connected to the medium-voltage DC capacitor; wherein,

The controller is used to determine, according to 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 adjustment of the medium charging of the high-voltage DC capacitor; 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, controlling the input The switch module completes the pre-charging of the traction auxiliary converter.

Further, the precharging device of the traction auxiliary converter further includes: a traction transformer and a traction motor;

The traction auxiliary converter further includes: a single-phase rectifier, a three-phase inverter, a non-isolated bidirectional DCDC module, a first switch connected to the non-isolated bidirectional DCDC module, an auxiliary inverter, and an auxiliary inverter connected to the auxiliary inverter. connected second switch;

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 high-voltage DC capacitor. The traction motor is connected; the energy storage element is connected with the first switch; the medium-voltage DC capacitor is respectively connected with the non-isolated bidirectional DCDC module and the auxiliary inverter; the second switch is connected with the three-phase medium Voltage AC bus connection.

Further, the input switch module is composed of a main contactor and a precharge module in parallel; the precharge module is composed of a precharge contactor and a precharge resistor in series.

In a second aspect, the present application provides a method for precharging a traction auxiliary converter, which is implemented by applying the precharging device for a traction auxiliary converter, and the method includes:

According to the state of the energy storage element and the three-phase medium-voltage AC bus, it is determined that one of the energy storage element, the three-phase medium-voltage AC bus and the input switch module is used to complete the charging of the medium-voltage DC capacitor;

By adjusting the pulse of the isolated bidirectional DCDC module, the direct current obtained after charging the medium-voltage direct-current capacitor is boosted, so as to complete the charging of the high-voltage direct-current capacitor;

The main contactor in the input switch module is controlled to be closed to complete the pre-charging of the traction auxiliary converter.

Further, according to the state of the energy storage element and the three-phase medium voltage AC bus, it is determined to use one of the energy storage element, the three-phase medium voltage AC bus and the input switch module to complete the operation of the medium voltage DC. capacity charging, including:

When the energy storage element is available and the three-phase medium voltage AC bus has no power, determining that the energy storage element is used to complete the charging of the medium voltage DC capacitor;

When the three-phase medium-voltage AC bus has electricity, it is determined that the three-phase medium-voltage AC bus is used to complete the charging of the medium-voltage DC capacitor;

When the energy storage element is unavailable and the three-phase medium-voltage AC bus has no power, it is determined that the input switch module is used to complete the charging of the medium-voltage DC capacitor.

Further, when the energy storage element is available and the three-phase medium voltage AC bus has no power, determining to use the energy storage element 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 has no power, the first switch in the precharging device is closed, and the energy storage element passes through the non-isolated bidirectional DCDC module in the precharging device Power is supplied to the medium voltage DC capacitor.

Further, when the three-phase medium-voltage AC bus has electricity, determining to use the three-phase medium-voltage AC bus to complete the charging of the medium-voltage DC capacitor includes:

When the three-phase medium-voltage AC bus has electricity, the second switch in the pre-charging device is closed, and the three-phase medium-voltage alternating current in the three-phase medium-voltage AC bus is applied to complete the charging of the medium-voltage DC capacitor. charging.

Further, according to the state of the energy storage element and the three-phase medium voltage AC bus, it is determined to use one of the energy storage element, the three-phase medium voltage AC bus and the input switch module to complete the operation of the medium voltage DC. capacity charging, also includes:

acquiring 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 direct-current capacitor is determined according to the initial voltage, termination voltage, instantaneous voltage, instantaneous current and sampling period of the medium-voltage direct-current capacitor.

Further, 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, further comprising:

acquiring the initial voltage, termination voltage, instantaneous voltage, instantaneous current and sampling period of the high-voltage DC capacitor;

The capacitance value of the high-voltage direct-current capacitor is determined according to the initial voltage, termination voltage, instantaneous voltage, instantaneous current and sampling period of the high-voltage direct-current capacitor.

In a fourth aspect, the present application provides a precharging system for a traction auxiliary converter, including: a train central controller and a plurality of the precharging devices for the traction auxiliary converter;

The pre-charging devices are connected via the three-phase medium-voltage AC bus;

The train central controller is respectively connected with the controllers of each pre-charging device;

The train central controller is used for determining the precharging sequence of each precharging device according to the state of the energy storage element of each precharging device.

It can be known from the above technical solutions that the present application provides a precharging device, system and method for a traction auxiliary converter. The device includes: a traction auxiliary converter and a three-phase medium-voltage AC bus; the traction auxiliary converter includes: a controller, an input switch module, an isolated bidirectional DCDC module, an energy storage element, a high-voltage DC capacitor and a medium-voltage DC capacitor; the controller is respectively connected with the input switch module and the isolated bidirectional DCDC module; the isolated bidirectional DCDC module is respectively connected with the high voltage DC capacitor, the medium voltage DC capacitor and the energy storage element; the input switch module 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 configured to, according to the state of the energy storage element and the three-phase medium-voltage AC bus, Determine 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; by adjusting the pulse of the isolated bidirectional DCDC module, the medium-voltage DC The DC power obtained after the capacitor is charged is boosted to complete the charging of the high-voltage DC capacitor; and, the input switch module is controlled to complete the pre-charging of the traction auxiliary converter, which can reduce the number of switching elements in the input switch module. The high current surge and operation frequency can help to improve the life of components and reduce the failure rate, which can improve the reliability of the pre-charging of the traction converter; The converter can still be pre-charged by other methods; during the pre-charging process, the capacitance value of the internal capacitance of the converter can be estimated, which can be used for the life prediction of the DC capacitor components of the converter, Internal self-inspection, etc.

Description of drawings

In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the following briefly introduces the accompanying drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are only These are some embodiments of the present application. For those of ordinary skill in the art, other drawings can also be obtained based on these drawings without any creative effort.

1 is a schematic structural diagram of a precharging device for a traction auxiliary converter in an embodiment of the present application;

2 is a schematic structural diagram of an isolated bidirectional DCDC module in an example of the present application;

3 is a schematic structural diagram of a non-isolated bidirectional DCDC module in an example of the present application;

FIG. 4 is a schematic structural diagram of an auxiliary inverter in an example of the present application;

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

6 is a schematic flowchart of a precharging method for a traction auxiliary converter in an embodiment of the present application;

FIG. 7 is a schematic flowchart of steps 110 to 130 of the method for precharging the traction auxiliary converter in the embodiment of the present application;

8 is a schematic flowchart of a precharging method for a traction auxiliary converter in an application example of the present application;

9 is a schematic flowchart of a train-level precharging method for a traction auxiliary converter in an application example of the present application;

FIG. 10 is a schematic structural diagram of a precharging system of a traction auxiliary converter in an embodiment of the present application.

Detailed ways

In order to make those skilled in the art better understand the technical solutions in this specification, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present application. Obviously, the described The embodiments are only a part of the embodiments of the present application, but not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present application.

The precharging device, system and method of the traction auxiliary converter disclosed in the present application can be used in the field of on-board energy storage, and can also be used in any field except the field of on-board energy storage. The pre-charging of the traction auxiliary converter disclosed in the present application The application fields of the apparatus, system and method are not limited.

Specifically, it will be described by the following embodiments.

In order to reduce the current impact and action frequency of the switching elements in the input switch module, help improve the life of the elements and reduce the failure rate, and thus improve the reliability of the pre-charging of the traction converter, the present application provides a traction auxiliary converter. An embodiment of the precharging device, as shown in FIG. 1 , specifically includes: a traction auxiliary converter and a three-phase medium-voltage AC bus; the traction auxiliary converter includes: a controller, an input switch module, and an isolated bidirectional DCDC module , energy storage element, high voltage DC capacitor and medium voltage DC capacitor; the controller is respectively connected with the input switch module and the isolated bidirectional DCDC module; the isolated bidirectional DCDC module is respectively connected with the high voltage DC capacitor, the medium voltage DC capacitor connected with the energy storage element; 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 for storing energy according to the The state of the element and the three-phase medium-voltage AC bus, determine the use of 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; by adjusting the isolation bidirectional The pulse of the DCDC module boosts the DC power obtained after charging the medium-voltage DC capacitor to complete the charging of the high-voltage DC capacitor; and controls the input switch module to complete the traction auxiliary converter. precharge.

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

In an example, as shown in FIG. 2 , port 1 of the isolated bidirectional DCDC module is connected to a high-voltage DC capacitor, and port 2 is connected to a medium-voltage DC capacitor. By adjusting the pulse width, phase shift angle or switching frequency of the isolated bidirectional DCDC module, the controller realizes the voltage regulation control of the medium voltage DC bus, and then supplies 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, a bidirectional active bridge converter. Q ₁ and Q ₂ are connected in series to form bridge arm 1, Q ₃ and Q ₄ are connected in series to form bridge arm 2, and Q ₅ and Q ₆ are connected in series to form a bridge arm 2. The bridge arm 3, Q ₇ and Q ₈ are connected in series to form the bridge arm 4. The bridge arms ₁ and ₂ are connected in parallel with the high voltage DC capacitor. The midpoints of the intermediate frequency transformer M are respectively connected to the primary winding of the intermediate frequency transformer M, and the midpoint of the bridge arm 2 is connected to the other end of the primary side of the intermediate frequency transformer M; It is connected to the secondary winding of the intermediate frequency transformer M.

As shown in FIG. 1 , in an embodiment of the present application, the precharging device for the traction auxiliary converter further includes: a traction transformer and a traction motor; the traction auxiliary converter further includes: a single-phase rectifier, A three-phase inverter, a non-isolated bidirectional DCDC module, a first switch connected to the non-isolated bidirectional DCDC module, an auxiliary inverter, and a second switch connected to the auxiliary inverter; one end of the input switch module is connected through the The single-phase rectifier is connected to the high-voltage DC capacitor, 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 The element is connected to the first switch; the medium voltage DC capacitor is respectively connected to the non-isolated bidirectional DCDC module and the auxiliary inverter; the second switch is connected to the three-phase medium voltage AC bus.

Specifically, the first switch is a switch component connecting the non-isolated bidirectional DCDC module and the energy storage element; 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 non-isolated bidirectional DCDC module is composed of switch tubes, inductors and capacitors. Buck-Boost circuits can be used here but are not limited to. The controller can control the charge and discharge currents of the energy storage elements by adjusting the pulses of the switch tubes; the auxiliary inverter can It is a three-phase inverter power module, which converts the DC power of the medium-voltage DC capacitor into three-phase AC power with pulse width modulation, and then connects to the three-phase medium-voltage AC bus of the train through the second switch. The controller detects the output voltage and current value of the three-phase inverter power module, and then adjusts the pulse of the switch tube to realize the controllable voltage and current of the auxiliary inverter.

In an example, as shown in FIG. 3 , the non-isolated bidirectional DCDC module is composed of switch tubes, inductors and capacitors. An improved Boost circuit can be used here but is not limited to; as shown in Figure 4, port 1 of the auxiliary inverter is connected to the medium-voltage DC bus, and port 2 is connected to the three-phase medium-voltage AC bus through the second switch. Q ₁₁ and Q ₁₂ are connected in series to form an A-phase bridge arm, Q ₁₃ and Q ₁₄ are connected in series to form a B-phase bridge arm, Q ₁₅ and Q ₁₆ are connected in series to form a C-phase bridge arm, and inductors _{La , L b ,} and L _c are three-phase filters The inductors, 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 the voltage and current regulation of the auxiliary inverter and the bidirectional conversion of energy.

As shown in FIG. 5 , in an embodiment of the present application, the input switch module is composed of a main contactor and a precharge module in parallel; the precharge module is composed of a precharge contactor and a precharge resistor in series.

Specifically, the input switch module is formed of a precharge contactor and a precharge resistor in series, and is connected in parallel with the main contactor; the controller can control the closing and opening of the precharge contactor and the main contactor.

In order to further illustrate the solution, the present application provides an application example of a traction auxiliary converter precharging device, which is specifically described as follows:

In this application example, the traction auxiliary converter precharging device (that is, the traction auxiliary converter precharging architecture) consists of an input switch module, an isolated bidirectional DCDC module, a non-isolated bidirectional DCDC module, a switch module, and an energy storage element. (energy storage elements include but are not limited to batteries), single-phase rectifiers, auxiliary inverters and controllers.

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 precharge contactor and the main contactor. One side of the input switch module is connected with the secondary winding of the traction transformer, and the other side is connected with the AC input end of the single-phase rectifier.

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 bridges on both sides of the intermediate frequency transformer can be two-level half-bridge, three-level For structures such as half bridges, in order to obtain higher power levels, the bridge arms can also be connected in series or cascaded.

The energy storage element consists of batteries, fuses, battery management systems and other components. The first switch is a switch component that connects the non-isolated bidirectional DCDC module and the energy storage element, and the first switch receives an instruction from the controller to implement on and off functions.

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 realizes the controllable charge and discharge current of the energy storage element by adjusting the pulse of the switch tube.

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

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

The control of the traction auxiliary converter pre-charging architecture is divided into two parts: single traction auxiliary converter pre-charging control and train-level pre-charging control.

In order to reduce the current impact and action frequency of the switching elements in the input switch module, help to improve the life of the elements and reduce the failure rate, and thus improve the reliability of the pre-charging of the traction converter, this embodiment provides an execution subject that is the control The pre-charging method of the traction auxiliary converter of the inverter is realized by applying the pre-charging device of the traction auxiliary converter, as shown in Fig. 6, the method specifically includes the following contents:

Step 100: According to the state of the energy storage element and the three-phase medium-voltage AC bus, it is determined to use one of the energy storage element, the three-phase medium-voltage AC bus and the input switch module to complete the operation of the medium-voltage DC capacitor. Charge.

Specifically, medium-voltage DC capacitor charging is performed: two charging modes can be further divided according to whether the energy storage element is connected or not. When the energy storage element is available and the medium voltage AC bus has no power, mode 1 can be used; when the medium voltage AC bus has power, mode two can be used; when the energy storage element is unavailable and the medium voltage AC bus has no power, the traditional input switch module is used Precharge. Traditionally, traction auxiliary converters are usually precharged with input switch modules.

Mode 1: Precharge with energy storage element. 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 the controlled mode, and the voltage of the medium-voltage DC capacitor is a direct current with a controllable amplitude higher than the voltage of the energy storage element. The non-isolated bidirectional DCDC module can also work in the uncontrolled mode. At this time, the switch tube does not operate and the diode element is turned on, so that the voltage of the medium voltage DC capacitor is equal to the voltage of the energy storage element. During the charging process, through the detection of the discharge current and voltage of the energy storage element, the charging instantaneous power curve of the medium-voltage DC capacitor is calculated, and the voltage rise curve of the medium-voltage DC capacitor is detected at the same time, so as to calculate the capacitance value of the medium-voltage DC capacitor.

Mode 2: Use the energy of the three-phase medium-voltage AC bus for pre-charging. The second switch is closed, and other traction auxiliary converters are used to output three-phase medium-voltage alternating current to complete the charging of the medium-voltage direct current capacitor. By detecting the voltage of the three-phase medium-voltage AC bus and the current input to the auxiliary inverter, the charging instantaneous power curve of the medium-voltage DC capacitor is calculated, and the voltage rise curve of the medium-voltage DC capacitor is detected at the same time, so as to calculate the capacitance value of the medium-voltage DC capacitor. .

Step 200 : boosting the DC power obtained after charging the medium voltage DC capacitor by adjusting the pulse of the isolated bidirectional DCDC module, so as to complete the charging of the high voltage DC capacitor.

Specifically, charging the high-voltage DC capacitor: the controller can charge the high-voltage DC capacitor after boosting the DC power of the medium-voltage DC capacitor by adjusting the pulse of the isolated bidirectional DCDC module. During the charging process, the high-voltage DC capacitor voltage is detected in real time. If the pre-charge setting value is reached within a limited time, such as the rated DC bus voltage of the converter, the pre-charging will be terminated. The isolated bidirectional DCDC module stopped working. If the voltage cannot reach the precharge set value within a limited time, end the precharge, and continue to try the precharge process several times. If the precharge set value is still not reached, the traction auxiliary converter is blocked. In the above process, through the detection of the discharge current and voltage of the isolated bidirectional DCDC module, the charging instantaneous power curve of the high-voltage DC capacitor is calculated, and the voltage rise curve of the medium-voltage DC capacitor is combined to calculate the capacitance value of the medium-voltage DC capacitor.

Step 300: Control the main contactor in the input switch module to close to complete the pre-charging of the traction auxiliary converter.

Specifically, the controller can control the main contactor in the input switch module to close to complete all precharging processes. After that, the single-phase rectifier can start to work, or it can work in the state of uncontrolled rectification. The single-phase rectifier converts the AC power input from the traction auxiliary converter into DC power on the high-voltage DC capacitor. The isolated bidirectional DCDC module starts to work, and converts the electric energy on the high-voltage DC capacitor into the 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 to work, closes the second switch, supplies power to the three-phase medium-voltage AC bus of the train, and provides AC power for the load on the bus.

In order to further improve the flexibility of the pre-charging of the traction auxiliary converter, thereby improving the reliability of the converter, referring to FIG. 7 , in an embodiment of the present application, step 100 includes:

Step 110: when the energy storage element is available and the three-phase medium voltage AC bus has no power, determine that the energy storage element is used to complete the charging of the medium voltage DC capacitor;

Step 120: When the three-phase medium-voltage AC bus has electricity, determine to use the three-phase medium-voltage AC bus to complete the charging of the medium-voltage DC capacitor;

Step 130: When the energy storage element is unavailable and the three-phase medium-voltage AC bus has no power, it is determined that the input switch module is used to complete the charging of the medium-voltage DC capacitor.

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

Step 111: When the energy storage element is available and the three-phase medium voltage AC bus has no power, close the first switch in the precharging device, and the energy storage element passes through the non-isolation in the precharging device. A bidirectional DCDC module supplies power to the medium voltage DC capacitor.

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 includes:

Step 121: When the three-phase medium-voltage AC bus has electricity, close the second switch in the pre-charging device, apply the three-phase medium-voltage AC in the three-phase medium-voltage AC bus, and complete the charging The charging of the voltage and DC capacitors.

In order to realize the estimation of the capacitance value of the capacitor on the basis of improving the reliability of the pre-charging of the traction auxiliary converter, and then realize the prediction of the life of the capacitor component, in an embodiment of the present application, step 110 further includes:

Obtain the initial voltage, termination voltage, instantaneous voltage, instantaneous current and sampling period of the medium voltage DC capacitor; determine the medium voltage according to the initial voltage, termination voltage, instantaneous voltage, instantaneous current and sampling period of the medium voltage DC capacitor The capacitance of the voltage DC capacitor.

Specifically, the initial voltage of the medium-voltage DC capacitor can represent the voltage when the medium-voltage DC capacitor starts charging, and the termination voltage can represent the voltage when the medium-voltage DC capacitor ends charging; it can be calculated according to the following formula:

Among them, C _M is the capacitance value of the medium voltage DC capacitor, U ₁ and U ₂ are the initial voltage and termination voltage of the medium voltage DC capacitor, respectively, _ui and _ii are the instantaneous voltage and current of the medium voltage DC bus, T _s is the sampling period.

In order to realize the estimation of the capacitance value of the capacitor on the basis of improving the reliability of the pre-charging of the traction auxiliary converter, and then realize the prediction of the life of the capacitor component, in an embodiment of the present application, step 120 further includes:

Obtain the initial voltage, termination voltage, instantaneous voltage, instantaneous current and sampling period of the high-voltage DC capacitor; determine the high-voltage DC capacitor according to the initial voltage, termination voltage, instantaneous voltage, instantaneous current and sampling period of the high-voltage DC capacitor capacity value.

Specifically, the initial voltage of the high-voltage DC capacitor can represent the voltage when the high-voltage DC capacitor starts charging, and the termination voltage can represent the voltage when the high-voltage DC capacitor ends charging; it can be calculated according to the following formula:

Among them, _CH is the capacitance of the high-voltage DC capacitor, U ₃ and U ₄ are the initial voltage and termination voltage of the high-voltage DC capacitor, respectively, u _j and _ij are the instantaneous voltage across the high-voltage DC capacitor and the instantaneous flow into the high-voltage DC capacitor, respectively. current, T _s is the sampling period.

Traditionally, the traction auxiliary converter is precharged by using the input switch module, as shown in FIG. 8 , the present application proposes a new precharging control method which is different from the traditional solution in combination with the above-mentioned traction auxiliary converter precharging device. Application examples are described as follows:

Step 1: Complete MV DC capacitor charging. According to whether the energy storage element is connected or not, 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 unavailable and the three-phase medium-voltage AC bus has no power , the traditional input switch module is used for precharging.

Mode 1: Precharge with energy storage element. 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, at which time the voltage of the medium voltage DC capacitor is a direct current with a controllable amplitude higher than the voltage of the energy storage element. The non-isolated bidirectional DCDC module can also work in the uncontrolled mode. At this time, the switch tube does not operate and the diode element is turned on, so that the voltage of the medium voltage DC capacitor is equal to the voltage of the energy storage element. During the charging process, through the detection of the discharge current and voltage of the energy storage element, the charging instantaneous power curve of the medium-voltage DC capacitor is calculated, and the voltage rise curve of the medium-voltage DC capacitor is detected at the same time, so as to calculate the capacitance value of the medium-voltage DC capacitor. Its specific calculation formula is:

Among them, C _M is the capacitance value of the medium voltage DC capacitor, U ₁ and U ₂ are the initial voltage and termination voltage of the medium voltage DC capacitor, respectively, _ui and _ii are the instantaneous voltage and current of the medium voltage DC bus, T _s is the sampling period.

Mode 2: Use the energy of the three-phase medium-voltage AC bus for pre-charging. The second switch is closed, and other traction auxiliary converters are used to output three-phase medium-voltage alternating current to complete the charging of the medium-voltage direct current capacitor. By detecting the voltage of the three-phase medium-voltage AC bus and the current input to the auxiliary inverter, the charging instantaneous power curve of the medium-voltage DC capacitor is calculated, and the voltage rise curve of the medium-voltage DC capacitor is detected at the same time, so as to calculate the capacitance value of the medium-voltage DC capacitor. . Its specific calculation formula is:

Among them, C _M is the capacitance value of the medium voltage DC capacitor, U ₁ and U ₂ are the initial voltage and termination voltage of the medium voltage DC capacitor, respectively, _ui and _ii are the instantaneous voltage and current of the medium voltage DC bus, T _s is the sampling period.

Step 2: Charge the HVDC capacitor. By adjusting the pulse of the isolated bidirectional DCDC module, the controller boosts the DC power of the medium voltage DC capacitor and charges it to the high voltage DC capacitor. During the charging process, the high-voltage DC capacitor voltage is detected in real time. If the pre-charge setting value is reached within a limited time, such as the rated DC bus voltage of the converter, the pre-charging will be terminated. The isolated bidirectional DCDC module stopped working. If the voltage cannot reach the precharge set value within a limited time, end the precharge, and continue to try the precharge process several times. If the precharge set value is still not reached, the traction auxiliary converter is blocked. In the above process, through the detection of the discharge current and voltage of the isolated bidirectional DCDC module, the charging instantaneous power curve of the high-voltage DC capacitor is calculated, and the voltage rise curve of the medium-voltage DC capacitor is combined to calculate the capacitance value of the medium-voltage DC capacitor. Its calculation formula is as follows:

Among them, _CH is the capacitance of the high-voltage DC capacitor, U ₃ and U ₄ are the initial voltage and termination voltage of the high-voltage DC capacitor, respectively, u _j and _ij are the instantaneous voltage across the high-voltage DC capacitor and the instantaneous flow into the high-voltage DC capacitor, respectively. current, T _s is the sampling period.

Step 3: Close the main contactor and start the traction auxiliary converter. The controller controls the main contactor in the input switch module to close to complete all pre-charging processes; after that, the single-phase rectifier can start to work, or it can work in an uncontrolled rectification state. The single-phase rectifier converts the AC power input from the traction auxiliary converter into DC power on the high-voltage DC capacitor. The isolated bidirectional DCDC module starts to work, and converts the electric energy on the high-voltage DC capacitor into the 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 to work, closes the second switch, supplies power to the three-phase medium-voltage AC bus of the train, and provides AC power for the load on the bus.

Further, referring to FIG. 9 , the train-level pre-charging control process includes: detecting whether the power of the energy storage element is available, and if so, select any traction auxiliary converter with available energy storage elements to send a pre-charging command, otherwise, select any traction auxiliary converter. The converter sends a pre-charging command; closes the medium-voltage AC bus contactor and sends a closing second switch command; detects whether the three-phase medium-voltage AC bus has electricity, and if so, sends a pre-charging command to other traction auxiliary converters; specific Described as follows:

Step 11: The train central control unit detects the state of the train energy storage element and selects the first pre-charged traction converter unit. If there are available energy storage elements on the train, select one of the traction auxiliary converters available for all energy storage elements to start pre-charging; if the energy storage elements of all traction auxiliary converters on the train are unavailable, Then choose one to start pre-charging.

Step 12: If the controller of the traction auxiliary converter receives an instruction to start precharging, the controller executes the precharging control strategy for a single traction auxiliary converter above.

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

Step 14: After detecting that the three-phase medium-voltage AC bus has electricity, the train central control unit sends a pre-charging command to all the remaining traction auxiliary converters.

In order to reduce the current impact and operation frequency of the switching elements in the input switch module, help to improve the life of the elements and reduce the failure rate, and thus improve the reliability of the pre-charging of the traction converter, as shown in FIG. 10 , the present application provides a An embodiment of a precharging system for traction auxiliary converters includes: a train central controller and a plurality of the precharging devices for traction auxiliary converters; the three-phase medium voltage AC bus is connected between the precharging devices. The train central controller is respectively connected with the controller of each precharging device; the train central controller is used for determining the precharging sequence of each precharging device according to the state of the energy storage element of each precharging device.

Specifically, any traction auxiliary converter can be the first to complete the precharge, and the first mode can be used, or the traditional precharge method can be used, that is, the input switch module can complete the precharge. All remaining traction auxiliary converters can then be precharged using mode two. It can be divided into four steps:

Step 1: After the central control unit of the train is powered on, it detects the state of the energy storage element of the train, and selects the first pre-charged traction converter unit. If there are available energy storage elements on the train, select one of the traction auxiliary converters available for all energy storage elements to start pre-charging. If the energy storage elements of all traction auxiliary converters on the train are unavailable, select one of them and start pre-charging.

Step 2, if the controller of the traction auxiliary converter receives an instruction to start precharging, the controller executes the precharging control strategy according to the above single traction auxiliary converter.

Step 3, the central control unit of the train controls the contactors between the medium voltage AC bus bars to close, and sends an instruction to close the second switch to all traction auxiliary converters.

Step 4: After the central control unit of the train detects that one traction auxiliary converter has completed pre-charging and the auxiliary inverter has completed the medium-voltage AC output, it orders all the remaining traction auxiliary converters to be pre-charged, and mode 2 is preferred. Precharge the traction auxiliary converter.

It can be seen from the above description that the pre-charging device, system and method for traction auxiliary converter provided by the present application can utilize the on-board energy storage to pre-charge the traction auxiliary converter of a rolling stock and control method, and has the ability to identify the health of the capacitor. Function; it can reduce the current impact and action frequency of the switching elements in the input switch module, help to improve the life of the components and reduce the failure rate, and then can improve the reliability of the pre-charging of the traction converter; specifically, it can significantly improve the converter When the heat of the pre-charging resistor is limited, the converter can still be pre-charged by other methods; during the pre-charging process, the capacitance value of the internal capacitance of the converter can be estimated, which can be used for the DC power of the converter Life prediction of capacitor components, internal self-inspection of the converter, etc.

Each embodiment of the above method in the present application is described in a progressive manner, and the same and similar parts between the various embodiments may be referred to each other, and each embodiment focuses on the differences from other embodiments. For related parts, please refer to the partial descriptions of the method embodiments.

As will be appreciated by those skilled in the art, the embodiments of the present application may be provided as a method, a system, or a computer program product. Accordingly, the present application may take the form of an entirely hardware embodiment, an entirely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, the present application may take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, etc.) having computer-usable program code embodied therein.

The present application is described with reference to flowchart illustrations and/or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the present application. It will be understood that each flow and/or block in the flowchart illustrations and/or block diagrams, and combinations of flows and/or blocks in the flowchart illustrations and/or block diagrams, can be implemented by computer program instructions. These computer program instructions may be provided to the processor of a general purpose computer, special purpose computer, embedded processor or other programmable data processing device to produce a machine such that the instructions executed by the processor of the computer or other programmable data processing device produce Means for implementing the functions specified in a flow or flow of a flowchart and/or a block or blocks of a block diagram.

These computer program instructions may also be stored in a computer-readable memory capable of directing a computer or other programmable data processing apparatus to function in a particular manner, such that the instructions stored in the computer-readable memory result in an article of manufacture comprising instruction means, the instructions The apparatus implements the functions specified in the flow or flow of the flowcharts and/or the block or blocks of the block diagrams.

These computer program instructions can also be loaded on a computer or other programmable data processing device to cause a series of operational steps to be performed on the computer or other programmable device to produce a computer-implemented process such that The instructions provide steps for implementing the functions specified in the flow or blocks of the flowcharts and/or the block or blocks of the block diagrams.

In this application, specific examples are used to illustrate the principles and implementations of the application, and the descriptions of the above examples are only used to help understand the method and the core idea of the application; The idea of the application will have changes in the specific implementation and application scope. To sum up, the content of this specification should not be construed as a limitation on the application.

Claims (10)

1. A precharge device for a traction-assist converter, comprising: a traction auxiliary converter and a three-phase medium-voltage alternating-current bus;

the traction-assist converter includes: the device comprises a controller, an input switch module, an isolation bidirectional DCDC module, an energy storage element, a high-voltage direct current capacitor and a medium-voltage direct current capacitor;

the controller is respectively connected with the input switch module and the isolated bidirectional DCDC module; the isolation bidirectional DCDC module is respectively connected with the high-voltage direct-current capacitor, the medium-voltage direct-current capacitor and the energy storage element; 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,

the controller is used for determining to use 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 the states of the energy storage element and the three-phase medium-voltage alternating-current bus; the direct current obtained after the medium-voltage direct current capacitor is charged is boosted by adjusting the pulse of the isolation bidirectional DCDC module so as to complete the charging of the high-voltage direct current capacitor; and controlling the input switch module to complete the pre-charging of the traction auxiliary converter.

2. The pre-charging apparatus of a traction-assist converter as claimed in claim 1, further comprising: a traction transformer and a traction motor;

the traction-assist converter further comprises: the system 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;

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

3. The pre-charging device of the traction auxiliary converter as claimed in claim 1, wherein the input switch module is composed of a main contactor and a pre-charging module in parallel; the pre-charging module is formed by connecting a pre-charging contactor and a pre-charging resistor in series.

4. A method for precharging a traction-assist converter, which is implemented by using a precharging apparatus for a traction-assist converter as claimed in any one of claims 1 to 3, the method comprising:

determining to use 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 the states of the energy storage element and the three-phase medium-voltage alternating-current bus;

the direct current obtained after the medium-voltage direct current capacitor is charged is boosted by adjusting the pulse of the isolation bidirectional DCDC module so as to complete the charging of the high-voltage direct current capacitor;

and controlling a main contactor in the input switch module to be closed to complete the pre-charging of the traction auxiliary converter.

5. The method of precharging a traction-assist converter as recited in claim 4, wherein said determining that charging of said medium voltage DC capacitor is completed using one of said energy storage element, a three-phase medium voltage AC bus and an input switch module based on the state of said energy storage element and a three-phase medium voltage AC bus comprises:

when the energy storage element is available and the three-phase medium-voltage alternating-current bus is electroless, determining that the energy storage element is applied to finish charging the medium-voltage direct-current capacitor;

when the three-phase medium-voltage alternating-current bus is electrified, determining that the three-phase medium-voltage alternating-current bus is used for charging the medium-voltage direct-current capacitor;

when the energy storage element is unavailable and the three-phase medium-voltage alternating-current bus is dead, determining that the input switch module is applied to finish charging the medium-voltage direct-current capacitor.

6. The method of precharging a traction-assist converter as recited in claim 5, wherein said determining that charging of said medium voltage DC capacitor is completed using said energy storage element when said energy storage element is available and said three phase medium voltage AC bus is dead comprises:

when the energy storage element is available and the three-phase medium-voltage alternating-current bus is dead, a first switch in the pre-charging device is closed, and the energy storage element supplies power to the medium-voltage direct-current capacitor through a non-isolated bidirectional DCDC module in the pre-charging device.

7. The method of precharging a traction-assist converter as recited in claim 5, wherein said determining that charging of said medium voltage DC capacitor is completed using said three-phase medium voltage AC bus when said three-phase medium voltage AC bus is charged comprises:

and when the three-phase medium-voltage alternating-current bus is electrified, closing a second switch in the pre-charging device, and applying the three-phase medium-voltage alternating current in the three-phase medium-voltage alternating-current bus to finish charging the medium-voltage direct-current capacitor.

8. The method of precharging a traction-assist converter as recited in claim 4, wherein said determining that charging of said medium voltage DC capacitor is completed using one of said energy storage element, a three-phase medium voltage AC bus and an input switch module is determined based on the state of said energy storage element and a three-phase medium voltage AC bus, further comprises:

acquiring initial voltage, final voltage, instantaneous current and sampling period of the medium-voltage direct-current capacitor;

and determining the capacitance value of the medium-voltage direct-current capacitor according to the initial voltage, the final voltage, the instantaneous current and the sampling period of the medium-voltage direct-current capacitor.

9. The method of pre-charging a traction-assist converter as claimed in claim 4, wherein the step-up of the DC voltage obtained after charging the medium voltage DC capacitor by adjusting the pulse of the isolated bidirectional DCDC module is performed to complete the charging of the high voltage DC capacitor, further comprising:

acquiring initial voltage, final voltage, instantaneous current and sampling period of the high-voltage direct-current capacitor;

and determining the capacitance value of the high-voltage direct current capacitor according to the initial voltage, the final voltage, the instantaneous current and the sampling period of the high-voltage direct current capacitor.

10. A pre-charge system for a traction-assist converter, comprising: a train central controller and a plurality of pre-charging devices for traction-assist converters according to any one of claims 1 to 3;

each pre-charging device is connected with each other through the three-phase medium-voltage alternating-current bus;

the train central controller is respectively connected with the controllers of the pre-charging devices;

and the train central controller is used for determining the pre-charging sequence of each pre-charging device according to the state of the energy storage element of each pre-charging device.

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