KR20210068212A - Discharge control apparatus and method for high voltage capacitors of semiconductor transformer used in train - Google Patents

Abstract

The present invention relates to a discharge control apparatus and a method for high voltage capacitors of a semiconductor transformer used in a train. The discharge control apparatus for high voltage capacitors of a semiconductor transformer used in a train, which includes a plurality of input capacitors and one output capacitor, includes: a discharge device connected in parallel only to the output capacitor; and a control unit for outputting a total command power to be transmitted from the input capacitor based on a difference between the output capacitor discharge command voltage and the output capacitor voltage (V_out), calculating one cell command power from the total command power, and switching and controlling the semiconductor elements of the input-side converter and the output-side converter of the railway vehicle semiconductor transformer according to a phase difference (D_Φ) of the output voltage between an input-side converter and an output-side converter of the semiconductor transformer, so as to control the discharge based on the phase difference (D_Φ).

Description

Discharging control apparatus and method of high voltage capacitor of semiconductor transformer of railway vehicle {DISCHARGE CONTROL APPARATUS AND METHOD FOR HIGH VOLTAGE CAPACITORS OF SEMICONDUCTOR TRANSFORMER USED IN TRAIN}

The present invention relates to an apparatus and method for controlling discharge of a high-voltage capacitor of a semiconductor transformer for a railway vehicle, and more particularly, to a semiconductor transformer for a railway vehicle having a plurality of input capacitors and one output capacitor, in which only the output capacitor is provided with a discharge device The present invention relates to an apparatus and method for controlling the discharge of a high-voltage capacitor of a semiconductor transformer of a railway vehicle, which enables discharge of an input capacitor as well as an output capacitor.

In general, a large-capacity transformer is used for AC line operation in railway vehicles.

At this time, the transformer commonly used in the railroad car serves to convert 60Hz/25kV of the AC line into 60Hz/1-2kV in a hydraulic manner.

However, recently, research is being conducted to apply a semiconductor transformer composed of a semiconductor/high-frequency transformer instead of a hydraulic/low-frequency transformer for high efficiency and light weight of railway vehicles. At this time, the semiconductor transformer is composed of a plurality of semiconductor elements, a plurality of high-frequency transformers, and a plurality of capacitors, and is used to replace the hydraulic/low-frequency transformer and converter of the existing railway vehicle.

On the other hand, power conversion devices (eg, transformers) used in railway vehicles have a function of discharging the high-voltage capacitor (ie, high-voltage capacitor) in the device when the operation is stopped. At this time, to discharge the high-voltage capacitor, the most common method is to connect the discharge resistor to the capacitor in parallel. However, since the discharge capacity is set small as the loss occurs in the regular discharge resistor, the actual power conversion device is discharged when the operation stops. The disadvantage is that it is remarkably slow.

Accordingly, in order to discharge the high-voltage capacitor for a short time, a method of connecting a resistor having a large discharge capacity connected in series with the semiconductor device in parallel to the capacitor is used (see FIG. 1 ). 1 is a circuit diagram exemplarily showing a conventional high-voltage capacitor discharge device.

As described above, the semiconductor transformer includes a plurality of semiconductor elements, a plurality of high-frequency transformers, and a plurality of high-voltage capacitors. Therefore, when the semiconductor transformer is stopped, the voltage applied to the high-voltage capacitor must be lowered to a low voltage in a short time. Accordingly, as shown in FIG. 1, a discharge device is used in which a discharge resistor having a large discharge capacity connected in series with a semiconductor device is connected in parallel to the high-voltage capacitor for short-time discharge of the high-voltage capacitor.

However, as shown in FIG. 2, in order to discharge the high-voltage capacitor in the conventional semiconductor transformer generally applied to railway vehicles, a discharge device is installed in two places per cell (eg, the high-voltage capacitor of the input-side converter and the high-voltage capacitor of the output-side converter). must be connected, and as the semiconductor transformer has a plurality of cells, the number of discharge devices increases in proportion to the number of cells. For reference, although FIG. 2 shows a semiconductor transformer composed of two cells, it may be composed of more cells.

In addition, in using the discharge device, not only a semiconductor device and a discharge resistor are added, but a gate driver circuit for driving a semiconductor device and a control wiring for controlling the semiconductor device must be included per one discharge device. Therefore, the complexity of the semiconductor transformer is complicated. not only increases, but also increases the size, weight, and unit cost.

As described above, since the semiconductor transformer of a railway vehicle includes a large number of high-voltage capacitors, if a discharge device for short-time discharge (that is, a discharge device in which a discharge resistor is connected in series to a semiconductor device) is connected to all capacitors, There is a problem of increasing the size, weight, and unit price.

Therefore, there is a need for a technology for discharging all high-voltage capacitors in a semiconductor transformer while minimizing the number of discharge resistors included in the discharge device.

The background technology of the present invention is disclosed in Korean Patent Laid-Open No. 10-2006-0050621 (published on May 19, 2006, a capacitor charging device, a semiconductor integrated circuit therefor, and a capacitor charging/discharging system).

According to one aspect of the present invention, the present invention was created to solve the above problems, and in a railway vehicle semiconductor transformer having a plurality of input capacitors and one output capacitor, a discharge device is provided only for the output capacitor, An object of the present invention is to provide an apparatus and method for controlling the discharge of a high-voltage capacitor of a railway vehicle semiconductor transformer, which enables discharge of an input capacitor as well as an output capacitor.

Discharge control apparatus of a high-voltage capacitor of a railway vehicle semiconductor transformer according to an aspect of the present invention, in the discharge control apparatus of a high-voltage capacitor of a railway vehicle semiconductor transformer comprising a plurality of input capacitors and one output capacitor, only the output capacitor Discharge devices connected in parallel; and calculating the total command power to be transmitted from the input capacitor based on the difference between the output capacitor discharge command voltage and the output capacitor voltage (V _{out ), and calculating one cell command power from the total command power, and the semiconductor transformer} in accordance with the input-side converter and a phase difference between the output voltage between the output-side converter (D _Φ), and the switching control of the semiconductor elements on the input side converter and the output converter of the railroad car semiconductor transformer, the discharge control of the phase difference (D _Φ) It characterized in that it comprises a; control unit to implement.

In the present invention, the control unit, based on Equation 1 below, calculates the power (P) delivered by _{the phase difference (D Φ} ) of the output voltage between the input-side converter and the output-side converter of the semiconductor transformer do it with

(Equation 1)

Here, V _in and V _out are the magnitude of the input/output voltage, D _Φ is the phase difference of the output voltage between the input/output converters, L is the transformer leakage inductance, n is the transformer turn ratio, and f _s is the frequency (f _s ).

In the present invention, the control unit, the output capacitor discharge command voltage and the output capacitor voltage (V _out ) based on the difference between the PI controller for calculating the total command power to be transmitted from the input capacitor; a cell command power calculation unit calculating one cell command power by dividing the total command power by the number of cells; and a phase difference calculator that finally calculates the phase difference _{D Φ} calculated using Equation 1 above.

In the present invention, the control unit calculates the output capacitor discharge command voltage based on Equation 3 below,

(Equation 3)

Here, V _{out, t = 0} is the initial voltage of the output capacitor, V _{in, t = 0} is the initial voltage _{of the input capacitor, V in} is characterized in that the input capacitor voltage.

In the present invention, _{in order to discharge the output capacitor voltage (V out} ) to the required voltage (V _R ) in the required time (t _R ), based on the following Equation 6, the discharge resistance of the discharge device (R) determine the value,

(Equation 6)

Here, C _t is characterized as a total energy value calculated from energy stored _in all input capacitors (C in ) and output capacitors (C _{out ).}

According to another aspect of the present invention, in the method for controlling the discharge of a high-voltage capacitor of a semiconductor transformer for a railway vehicle, the method for controlling the discharge of a high-voltage capacitor of a semiconductor transformer for a railway vehicle, when the semiconductor transformer of the railway vehicle is stopped, the controller is switching on the device; measuring, by the control unit, the current input capacitor voltage and the output capacitor voltage, and automatically selecting an output capacitor discharge command voltage based on this in real time; and the control unit calculates the total command power to be delivered from the input capacitor based on the difference between the output capacitor discharge command voltage and the output capacitor voltage (V _{out ), and calculates one cell command power from the total command power,} and controlling the semiconductor elements of the input-side converter and the output-side converter according to the phase difference (D _Φ ) calculated according to the method to perform discharge control based on _{the phase difference (D Φ).}

In the present invention, _{after the step of performing the discharge control by the phase difference (D Φ} ), the controller discharges the output capacitor until the output capacitor voltage (V _out ) becomes smaller than the specified target voltage (VL). Repeatingly performing the step of automatically selecting the command voltage in real time to the step of performing the discharge control by _{the phase difference (D Φ);} and when the output capacitor voltage (V _out ) becomes smaller than a specified target voltage (VL), switching off, by the controller, a power semiconductor element of the discharge device.

In the present invention, in _{the step of performing the discharge control by the phase difference (D Φ} ), the control unit, based on Equation 1 below, the phase difference of the output voltage between the input-side converter and the output-side converter of the semiconductor transformer It is characterized in that the power (P) delivered by (D _{Φ) is calculated.}

(Equation 1)

Here, V _in and V _out are the magnitude of the input/output voltage, D _Φ is the phase difference of the output voltage between the input/output converters, L is the transformer leakage inductance, n is the transformer turn ratio, and f _s is the frequency (f _s ).

In the present invention, the control unit, the output capacitor discharge command voltage and the output capacitor voltage (V _out ) based on the difference between the PI controller for calculating the total command power to be transmitted from the input capacitor; a cell command power calculation unit calculating one cell command power by dividing the total command power by the number of cells; and a phase difference calculator that finally calculates the phase difference _{D Φ} calculated using Equation 1 above.

In the present invention, in _{the step of performing discharge control by the phase difference (D Φ} ), the control unit calculates the output capacitor discharge command voltage based on Equation 3 below,

(Equation 3)

Here, V _{out, t = 0} is the initial voltage of the output capacitor, V _{in, t = 0} is the initial voltage _{of the input capacitor, V in} is characterized in that the input capacitor voltage.

In the present invention, in _{the step of performing the discharge control by the phase difference (D Φ} ), the control unit, the output capacitor voltage (V _out ) to the required voltage (V _R ) to the required time (t _R ) In order to discharge, a value of the discharge resistance (R) of the discharge device is determined based on Equation 6 below,

(Equation 6)

Here, C _t is characterized as a total energy value calculated from energy stored _in all input capacitors (C in ) and output capacitors (C _{out ).}

According to one aspect of the present invention, in a railway vehicle semiconductor transformer having a plurality of input capacitors and one output capacitor, a discharge device is provided only on the output capacitor to discharge the output capacitor as well as the input capacitor. let it be

1 is a circuit diagram exemplarily showing a conventional high-voltage capacitor discharge device.
2 is an exemplary view showing a semiconductor transformer applied to a conventional railway vehicle.
3 is an exemplary view showing a schematic configuration of a discharge control device of a high-voltage capacitor of a semiconductor transformer of a railway vehicle according to an embodiment of the present invention.
4 is an exemplary view showing the output voltage and output current waveforms of the input-side converter and the output-side converter of the railway vehicle semiconductor transformer in FIG. 3 .
5 is an exemplary view showing the configuration of a control unit that performs phase control for generating a phase difference between the two converters in FIG. 3 .
6 is a flowchart for explaining a method of operating a control device for a discharge device of a high-voltage capacitor of a semiconductor transformer of a railway vehicle according to an embodiment of the present invention.
FIG. 7 is an exemplary view showing a change graph of an input-side converter current when an output capacitor voltage is adjusted according to the present embodiment in FIG. 3 .
FIG. 8 is an exemplary view showing a change graph of the input-side converter current when the discharge control according to the present embodiment is not performed, as compared with FIG. 7 .

Hereinafter, an embodiment of an apparatus and method for controlling discharge of a high-voltage capacitor of a semiconductor transformer of a railway vehicle according to the present invention will be described with reference to the accompanying drawings.

In this process, the thickness of the lines or the size of the components shown in the drawings may be exaggerated for clarity and convenience of explanation. In addition, the terms to be described later are terms defined in consideration of functions in the present invention, which may vary according to the intention or custom of the user or operator. Therefore, definitions of these terms should be made based on the content throughout this specification.

3 is an exemplary view showing a schematic configuration of a discharge control device of a high-voltage capacitor of a semiconductor transformer of a railway vehicle according to an embodiment of the present invention.

The high-voltage capacitor present in the semiconductor transformer for a railway vehicle according to the present embodiment includes a plurality of input capacitors and one output capacitor (that is, a plurality of output capacitors connected in series are considered as one output capacitor), as shown in FIG. As described above, in the present embodiment, the discharge device 100 is connected only to the output capacitor, and discharge of the input capacitor as well as the output capacitor is performed through the discharge device 100 .

In this case, the operation of the control unit 200, which is not described, will be described with reference to FIG. 5 .

4 is an exemplary view showing the output voltage and output current waveforms of the input-side converter and the output-side converter of the railway vehicle semiconductor transformer in FIG. 3, and the energy stored in the input capacitor is transferred to the output capacitor through the input-side converter and the transformer. , At this time, the input-side converter and the output-side converter operate as shown in FIG. 4 , and a current is generated in the transformer by the phase difference between the output voltages of the two converters (ie, the input-side converter and the output-side converter) and power is transmitted.

In the graphs shown in (a) and (b) of FIG. 4, the power delivered by the phase difference between the transformer input voltage and the transformer output voltage is calculated as in Equation 1 below, and the magnitude of the input/output voltage (V _in , V _out ), the phase difference of the output voltage between the input and output converters (D _Φ ), the transformer leakage inductance (L), the transformer turn ratio (n), and the frequency (f _s ) are determined.

A voltage level difference is generated by the transformer turn ratio n.

Meanwhile, when the discharge switch (ie, the discharge semiconductor device) of the discharge device 100 shown in FIG. 3 is operated, the voltage of the output capacitor is discharged over time, but the voltage of the input capacitor is maintained as it is.

Therefore, in order to discharge the input capacitor together, power transmission through control of the operation of the two converters is required. That is, the current is generated in the transformer by the phase difference of the output voltages of the two converters (ie, the input-side converter and the output-side converter), and the energy stored in the input capacitor must be transferred to the output capacitor through the input-side converter and the transformer. At this time, the transmitted power is determined by the _{phase difference (D Φ) as shown in Equation (1).} The controller 200 performs phase control by switching semiconductor devices of the two converters (ie, an input-side converter and an output-side converter) so that the phase difference D _{Φ occurs.}

FIG. 5 is an exemplary diagram illustrating the configuration of a control unit that performs phase control for generating a phase difference between two converters in FIG. 3 .

As shown in FIG. 5 , the controller 200 includes a proportional integral (PI) controller 210 , a cell command power calculator 220 , and a phase difference calculator 230 .

The control unit 200 _{controls only the output capacitor voltage V out} , and the PI controller 210 transmits it from the input capacitor based on the difference between the “output capacitor discharge command voltage” and the “output capacitor voltage V _{out ”} The total command power to be calculated is output, and the cell command power calculation unit 220 divides the total command power by the number of cells to calculate and output one cell command power, and the phase difference calculation unit 230 divides the total command power by the number of cells. The phase difference (D _Φ ) calculated using Equation 1 is finally calculated.

The controller 200 is to control the semiconductor switching element of the two converters (i.e., the input side converter, the output-side converter) according to the final calculation of the phase difference _(Φ D).

At this time, the instantaneous power P discharged by the discharge resistor R connected in parallel to the output capacitor is determined as in Equation 2 below.

At this time, in order for the output capacitor voltage to be constant, constant power must be supplied from the input capacitor as much as the power consumed by the discharge resistor.

Accordingly, as the power supply time increases, the voltage of the input capacitor decreases, the current flowing through the input-side converter increases for the same power supply, and when the voltage becomes very small, the current may increase infinitely. However, since the semiconductor device used in the input-side converter cannot operate beyond the rated current, the output capacitor voltage must be appropriately controlled to prevent the current from increasing indefinitely.

Therefore, in this embodiment, "output capacitor discharge command voltage" is applied as in Equation 3 in order to prevent overcurrent of the semiconductor device used in the converter.

Where V _{out, t = 0} is the initial voltage of the output _capacitor, V _{in, t = 0} is the initial voltage, V _in the input capacitor is a capacitor type voltage.

As shown in Equation 3, the “output capacitor discharge command voltage” decreases as much as the rate at which the _{input capacitor voltage V in decreases.}

At this time, the output capacitor voltage (V _out ) changes with time as shown in Equation 4, R is the discharge resistance value, and C _t is stored _in all input capacitors (C in ) and output capacitors (C _{out ) as shown in Equation 5} It is the total energy value calculated from energy.

_{In order to discharge the output capacitor voltage (V out} ) to the required voltage (V _R ) in the required time (t _R ) through the method according to this embodiment, it is necessary to determine an appropriate discharge resistance value. From Equation 4, it can be calculated as Equation 6 below.

At this time, since the input capacitor voltage (V _in ) and the output capacitor voltage (V _out ) change in the ratio of Equation (3), a required voltage can be set based on the _{input capacitor voltage (V in ).}

6 is a flowchart for explaining a method of operating a control device for a discharge device of a high-voltage capacitor of a semiconductor transformer of a railway vehicle according to an embodiment of the present invention.

Referring to FIG. 6 , when the railway vehicle semiconductor transformer is stopped ( S101 ), the controller 200 short-circuits (ie, switches on) the power semiconductor element of the discharge device for discharging ( S102 ).

The control unit 200 measures the current input capacitor voltage and the output capacitor voltage (S103), and the output capacitor discharge command voltage is automatically selected in real time according to Equation 3 (S104).

The control unit 200 calculates the total command power to be transmitted from the input capacitor based on the difference between the "output capacitor discharge command voltage" and the "output capacitor voltage (V _{out )", and one cell command from the total command power} By calculating power and switching the semiconductor elements of the two converters (ie, the input-side converter and the output-side converter) according to the _{phase difference (D Φ ) calculated using Equation 1, the phase difference (D Φ} ) discharge control is performed (S105).

In addition, the controller 200 _{repeatedly performs steps S103 to S106 until the output capacitor voltage V out} becomes smaller than the specified target voltage VL ( S106 ), and the output capacitor voltage V _out ) is smaller than the specified target voltage VL, the control unit 200 opens (ie, switches off) the power semiconductor element of the discharge device 100 ( S107 ).

7 is an exemplary view showing a change graph of the input-side converter current when the output capacitor voltage is adjusted according to the present embodiment in FIG. 3, and as shown in FIG. 7(d), based on Equation 3 It can be seen that when discharging is performed while adjusting the output capacitor voltage, the current does not increase, and the input-side converter current also decreases gradually as the input capacitor voltage of each module (ie, cell) gradually decreases.

8 is an exemplary view showing a change graph of the input-side converter current when the discharge control according to the present embodiment is not performed in comparison with FIG. 7, and as shown in FIG. 8(d), the output capacitor voltage is not adjusted. It can be seen that when the discharge is performed while maintaining the constant voltage, the input-side converter current gradually increases as the input capacitor voltage of each module (ie, cell) decreases.

As described above, the present invention has been described with reference to the embodiment shown in the drawings, but this is merely exemplary, and various modifications and equivalent other embodiments are possible therefrom by those of ordinary skill in the art. will understand the point. Therefore, the technical protection scope of the present invention should be defined by the following claims. Also, the implementations described herein may be implemented as, for example, a method or process, an apparatus, a software program, a data stream, or a signal. Although discussed only in the context of a single form of implementation (eg, only as a method), implementations of the discussed features may also be implemented in other forms (eg, in an apparatus or a program). The apparatus may be implemented in suitable hardware, software and firmware, and the like. A method may be implemented in an apparatus such as, for example, a processor, which generally refers to a computer, a microprocessor, a processing device, including an integrated circuit or programmable logic device, or the like. Processors also include communication devices such as computers, cell phones, portable/personal digital assistants ("PDAs") and other devices that facilitate communication of information between end-users.

100: discharge device 200: control unit
210: PI controller 220: cell command power calculation unit
230: phase difference calculator

Claims (11)

An apparatus for controlling the discharge of a high-voltage capacitor of a railway vehicle semiconductor transformer including a plurality of input capacitors and one output capacitor, the apparatus comprising:
a discharge device connected in parallel only to the output capacitor; and
Calculate the total command power to be delivered from the input capacitor based on the difference between the output capacitor discharge command voltage and the output capacitor voltage (V _{out ), and calculate one cell command power from the total command power,} According to the phase difference (D _Φ ) of the output voltage between the input-side converter and the output-side converter, the semiconductor element of the input-side converter and the output-side converter of the railway vehicle semiconductor transformer is switched and controlled to perform discharge control by _{the phase difference (D Φ)} A control unit for controlling the discharge of a high-voltage capacitor of a semiconductor transformer of a railway vehicle, characterized in that it comprises a.
According to claim 1, wherein the control unit,
Based on Equation 1 below, the high-voltage capacitor of a semiconductor transformer for a railway vehicle, characterized in that the electric power (P) transferred by _{the phase difference (D Φ} ) of the output voltage between the input-side converter and the output-side converter of the semiconductor transformer is calculated of discharge control device.
(Equation 1)

Here, V _in and V _out are the magnitude of the input/output voltage, D _Φ is the phase difference of the output voltage between the input/output converters, L is the transformer leakage inductance, n is the transformer turn ratio, and f _s is the frequency (f _s ).
According to claim 2, wherein the control unit,
a PI controller for calculating the total command power to be transmitted from the input capacitor based on the difference between the output capacitor discharge command voltage and the output capacitor voltage (V _{out );}
a cell command power calculation unit calculating one cell command power by dividing the total command power by the number of cells; and
Discharge control device of a high-voltage capacitor of a semiconductor transformer of a railway vehicle, comprising a; a phase difference calculator that finally calculates the _{phase difference (D Φ} ) calculated using Equation (1).
According to claim 1, wherein the control unit,
Calculate the output capacitor discharge command voltage based on Equation 3 below,
(Equation 3)

Here, V _{out, t = 0} is the initial voltage of the output capacitor, V _{in, t = 0} is the initial voltage _{of the input capacitor, V in} is the input capacitor voltage, characterized in that the discharge control device of the high-voltage capacitor of a railway vehicle semiconductor transformer.
According to claim 1, wherein the control unit,
In order to discharge the output capacitor voltage (V _out ) to the required voltage (V _R ) in the required time (t _R ), the discharge resistance (R) value of the discharge device is determined based on Equation 6 below,
(Equation 6)

Here, C _{t is the total energy value calculated from the energy stored in} all the input capacitors (C in ) and the output capacitors (C _out ) Discharge control device of the high-voltage capacitor of a railway vehicle semiconductor transformer.
A method for controlling discharge of a high-voltage capacitor of a semiconductor transformer of a railway vehicle,
When the railway vehicle semiconductor transformer is stopped, the control unit switching on the power semiconductor element of the discharge device;
measuring, by the control unit, the current input capacitor voltage and the output capacitor voltage, and automatically selecting an output capacitor discharge command voltage based on this in real time; and
The control unit calculates the total command power to be transmitted from the input capacitor based on the difference between the output capacitor discharge command voltage and the output capacitor voltage (V _{out ), calculates one cell command power from the total command power, and a specified method} According to the calculated phase difference (D _Φ ) according to the switching control of the semiconductor elements of the input-side converter and the output-side converter _{to perform discharge control by the phase difference (D Φ} ); Railroad vehicle semiconductor comprising a Discharge control method of high voltage capacitor of transformer.
7. The method of claim 6,
After the step of performing discharge control by the phase difference (D _Φ),
The control unit automatically selects the output capacitor discharge command voltage in real time until the output capacitor voltage (V _out ) becomes smaller than the specified target voltage (VL) or discharge control by _{the phase difference (D Φ)} repeating the step of performing; and
When the output capacitor voltage (V _out ) becomes smaller than the specified target voltage (VL), the control unit switches off the power semiconductor element of the discharge device; Discharge control method.
7. The method of claim 6,
In the step of performing discharge control by the phase difference (D _Φ),
The control unit is
Based on Equation 1 below, the high-voltage capacitor of a semiconductor transformer for a railway vehicle, characterized in that the electric power (P) transferred by _{the phase difference (D Φ} ) of the output voltage between the input-side converter and the output-side converter of the semiconductor transformer is calculated of discharge control method.
(Equation 1)

Here, V _in and V _out are the magnitude of the input/output voltage, D _Φ is the phase difference of the output voltage between the input/output converters, L is the transformer leakage inductance, n is the transformer turn ratio, and f _s is the frequency (f _s ).
The method of claim 8, wherein the control unit,
a PI controller for calculating the total command power to be transmitted from the input capacitor based on the difference between the output capacitor discharge command voltage and the output capacitor voltage (V _{out );}
a cell command power calculation unit calculating one cell command power by dividing the total command power by the number of cells; and
A discharge control method of a high-voltage capacitor of a semiconductor transformer for a railway vehicle, comprising a; a phase difference calculator that finally calculates the _{phase difference (D Φ} ) calculated by using Equation (1).
7. The method of claim 6,
In the step of performing discharge control by the phase difference (D _Φ),
The control unit is
Calculate the output capacitor discharge command voltage based on Equation 3 below,
(Equation 3)

Here, V _{out, t = 0} is the initial voltage of the output capacitor, V _{in, t = 0} is the initial voltage _{of the input capacitor, V in} is the input capacitor voltage, characterized in that the discharge control method of the high-voltage capacitor of a railway vehicle semiconductor transformer.
7. The method of claim 6,
In the step of performing discharge control by the phase difference (D _Φ),
The control unit is
In order to discharge the output capacitor voltage (V _out ) to the required voltage (V _R ) in the required time (t _R ), the discharge resistance (R) value of the discharge device is determined based on Equation 6 below,
(Equation 6)

where C _t is the total energy value calculated from the energy stored _in all input capacitors (C in ) and output capacitors (C _{out ).}

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