KR20120066376A - The brake chopper apparatus for propulsion system of ktx high speed train - Google Patents

Abstract

PURPOSE: A brake chopper device of a KTX high-speed railway propulsion control system is provided to simplify configuration of a main circuit by using two high power IGBT(Insulated Gate Bipolar Transistor)s. CONSTITUTION: An IGBT(100) is parallely connected with a load resistance(110). A snubber circuit(200) is parallely connected with the IGBT. The snubber circuit restricts overvoltage. The snubber circuit is composed of a snubber capacitor(210), a snubber diode(220), and a snubber resistance(230). The snubber diode and the snubber resistance are parallely connected with the snubber capacitor. A reflux diode interlinks an emitter and a collector of the IGBT. The snubber circuit is parallely connected with the reflux diode. The snubber circuit is cooled by a heat pipe type forced air cooling method.

Description

Brake Chopper Device for High Speed Railway Propulsion Control System {THE BRAKE CHOPPER APPARATUS FOR PROPULSION SYSTEM OF KTX HIGH SPEED TRAIN}

The present invention relates to a braking chopper device of a high speed railway propulsion control system of a TV, and more specifically, two large-power IGBTs (Insulated) instead of about ten power devices including a conventional two series gate turn off (GTO) device. By constructing main circuit using Gate Bipolar Transistor), it greatly improves reliability, and adopts heat pipe type forced air cooling to improve maintenance and reduce loss to prevent temperature rise inside propulsion control system. A braking chopper device for a control system.

Currently, the high-speed railway vehicles operating in Korea use power-intensive synchronous motor type propulsion control.

The propulsion control system of the TV is operated by the current-type converter / inverter method using the thyristor series for high power rather than the voltage-type converter / inverter which is commonly used in railway vehicles.

As described above, in the case of using a current source power circuit, the energy source supplied to the motor is in charge of a direct current inductor, and in reverse, the energy supplied from the converter is accumulated in the direct current inductor. Because it is superimposed on the converter, it is possible to return the current energy accumulated through the inverter operation to the tank line side.

In the TC propulsion control system, the accumulated energy is used in three ways.

For example, the converter is used as a top-level operation to regenerate power to the tramline. In the next-level operation, the power is used as the supply power for the internal blower inverter. Finally, the train passes the dead section. In the case where the regeneration to the tank line is inevitable due to the high supply voltage, the electric power consumed by dissipating the thermal energy by using the braking resistor is consumed.

In all of these operations, a current chopper system is used to control the flow of current in the series loop inside the system, which is Brake's Brake chopper system.

The braking chopper system of the high speed railway is composed of a current source, in which a general chopper system is composed of a voltage source and a load is connected in series to a chopper so that a stepped or stepped up voltage is supplied, and the load is connected in parallel with the chopper. Do.

That is, by controlling the conduction ratio of the current flowing through the chopper and the load, the method of reducing the magnitude of the average current in the entire series system is taken.

Therefore, the magnitude of the voltage applied to the both ends of the chopper is always fluctuate, and it is not easy to analyze the entire circuit since the conduction ratio is controlled for a fixed load.

On the other hand, the applied main circuit element is a GTO-diode circuit configuration in the form of two series circuits due to fluctuations in supply voltage, and protects the device by using a typical L-R-C-D snubber.

In the case of GTO thyristors, most manufacturers no longer manufacture new devices for small-capacity devices that are not intended for superpower control.

Accordingly, even in the high-speed railway, the high speed train suffers difficulties in troubleshooting due to the discontinuance of the device in the peripheral ring system, and the complex refrigerant snubber circuit and the liquid refrigerant deposition method of the cooling device for heat dissipation also become a major factor to make maintenance difficult. .

More specifically, as shown in FIG. 1 showing the structure of a brake chopper system used for controlling regenerative power and braking control of a train among propulsion control systems of currently operating high speed railway vehicles, the input / output terminals of the brake chopper and the load resistance are parallel to each other. Is connected.

Therefore, the brake chopper is normally disconnected from the current circuit because the main contactor (K-TT-01) is closed and the brake contactors (K-BK-01, K-BK-02) are open. It is fed in series to the current circuit.

At this time, when the brake chopper is off, the braking resistor (ZB-BK-01) is connected in series, and all current flowing through the propulsion control circuit passes through the resistor, so most of the regenerative energy generated from the motor is dissipated through the resistor. Done.

In this case, the railroad car is rapidly deteriorated, so there is a risk of an accident, and to compensate for this, a brake chopper must be used. In other words, if the conduction ratio of the braking chopper is continuously controlled, the braking resistor and the chopper device appear as if they are variable skin resistance, so that the necessary braking amount can be controlled (see FIG. 2).

On the other hand, the braking chopper performs an important function even in the regenerative operation to the tank line side. For example, the regenerative current is returned to the side line by the reverse operation of the input converter. Can't.

Accordingly, in the propulsion control system, a complex control structure provided by the input converter is in charge of the regenerative control and the braking chopper is used for smooth control performance.

In the snubber circuit, two pairs of off snubbers composed of L-R-C-D, which are frequently used for GTO switches, are connected to respective GTOs. Snubber diodes and high-speed capacitors are deposited inside liquid-cooling enclosures, and bulky inductors and resistors are externally mounted using wiring.

In addition, there are two sets of capacitors, which are composed of ten elements and a series in parallel, inside the enclosure, but there is a lot of room for improvement from the viewpoint of maintenance because the structure is very complicated and generates a lot of heat.

The present invention was created due to the necessity of improvement in the related art as described above. The high voltage IGBT (Insulated Gate Bipolar Transistor) is applied to a brake chopper device which is essential for regeneration and braking of electric power in the propulsion control system of a KTX high speed railway vehicle. By constructing the new chopper device, the main circuit is greatly simplified compared to the existing system, the reliability of the snubber circuit is maximized according to the characteristics of the system operating in parallel with the load, and the maintenance is possible through the forced air cooling method. The main purpose is to provide a braking chopper device for the new type of high speed railway propulsion control system which can improve the temperature and reduce the loss of the propulsion control system.

The present invention provides a braking chopper device of a high speed railway propulsion control system of the TV, as a means for achieving the above object; At least one Insulated Gate Bipolar Transistor (IGBT) connected in parallel with a load resistor; Provided is a brake chopper device for a high speed railway propulsion control system of the TV high speed rail, comprising a snubber circuit of the off snubber type connected in parallel to the IGBT to limit the overvoltage.

At this time, the snubber circuit is characterized in that it is composed of a snubber capacitor, a snubber diode and a snubber resistor.

In addition, the snubber circuit is connected in parallel with a reflux diode connecting the collector and the emitter of the IGBT, and the snubber diode and the snubber resistor are also characterized in that they are connected in parallel with the snubber capacitor.

In addition, the snubber circuit is characterized in that it is cooled by heat pipe type forced air cooling (steel providing cooling).

According to the present invention, the main circuit can be simply configured by using two large power IGBTs instead of about 10 power devices including the existing two-series GTO devices, which simplifies the configuration of the main circuit and facilitates control. It is accurate and greatly improves reliability, and it is easy to maintain by adopting the forced pipe type of heat pipe type, and the loss is reduced by that, so that the temperature rise inside the propulsion control device can be suppressed.

1 is a circuit configuration diagram of a conventional GTO braking chopper mounted on a BT high speed rail vehicle.
FIG. 2 is a waveform diagram illustrating an operation waveform of a main device according to FIG. 1.
3 is a circuit diagram of an IGBT brake chopper for a TV high speed rail vehicle according to the present invention.
4 is a circuit diagram illustrating an equivalent circuit of the brake chopper including the snubber circuit according to FIG. 3.
5A and 5B are graphs confirming whether spikes are generated at voltages across the switch with or without snubber circuits.
Figure 6 is an equivalent circuit diagram for confirming the cooling performance of the IGBT braking chopper for the TV high-speed railway vehicle according to the present invention.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

As shown in FIG. 3, the IGBT braking chopper device for a BT high-speed railway vehicle according to the present invention operates with a circuit configuration connected in parallel with a load resistor (braking resistor) 110 as before, and the configuration is simplified as a main circuit element. IGBT 100 is used.

In addition, the IGBT 100 includes a snubber circuit 200 connected to the IGBT 100 to limit the overvoltage generated when the switch-off occurs due to parasitic inductance included in the circuit.

At this time, the snubber circuit 200 is connected in parallel with the reflux diode 120 connecting the collector (C) and the emitter (E), the snubber capacitor 210, snubber diode 220 and snubber Including a nubber resistor 230, the snubber diode 220 and the snubber resistor 230 are connected in series with the snubber capacitor 210, respectively.

That is, the snubber diode 220 and the snubber resistor 230 are connected in parallel to each other.

Therefore, when the parasitic inductance occurs when switching off, the parasitic inductance is moved to the snubber capacitor 210, the spike voltage is limited, and at this time, the stored energy is discharged through the snubber resistor 230, it is possible to suppress the overvoltage Will be.

In addition, in the case of the IGBT 100, the power IGBT released to date has a tendency to rapidly increase as the allowable voltage increases, so considering the sufficient voltage margin, the 6500V class IGBT may be used, but V _{CE (SAT)} is 5.3. It reaches V (at 125 ° C) and the conduction loss is very large, so its practicality is low.

In the present invention to solve this problem was solved by applying a heat pipe type forced air cooling type, in the embodiment used a 4500V / 600A class two parallel IGBT structure.

And, the maximum output of the braking chopper is very large, instantaneous performance of 2.2MW class, while the existing device performs a switching operation at 300Hz, in the device according to the present invention has an improved switching operation of 500Hz ~ 1kHz.

Here, the design specifications of the brake chopper device of the present invention shown in Figure 3 are as follows.

(1) Input voltage: 0 ~ 3000V variable

(2) Output current: 0 ~ 800A variable

(3) Snubber circuit: R-C-D off snubber

(4) Power semiconductors: IGBT 4.5kV / 600A 2P

(5) Circuit method: current type parallel load chopper circuit

(6) Cooling method: heat pipe forced air cooling

(7) Operating frequency: 500 Hz or 1 kHz

On the other hand, since the chopper circuit of the brake chopper device according to the present invention is a load parallel type chopper device that operates as a current source, the analysis conditions are different from the general chopper method using a voltage source.

Therefore, the equivalent circuit of the brake chopper including the snubber circuit is displayed as shown in FIG. 4, and the analysis conditions are limited as follows in consideration of the characteristics of the chopper circuit.

(a) The snubber circuit applies an off snubber composed of R-C-D.

(b) The braking resistor R _Z is always connected in parallel with the IGBT.

(c) The parasitic circuit inside the IGBT is negligible because it is very small compared to the parasitic components of the real circuit.

(d) The current I _F flowing through the braking circuit is always assumed to be continuous during the chopper circuit operation. Therefore, even if the chopper IGBT is off, current continues to flow through the load resistor R _L and the braking resistor R _Z.

(e) The reflux current flowing through the reflux diode inside the IGBT does not occur due to the configuration of the circuit.

Under these conditions, if the motion is analyzed for the equivalent circuit, it is interpreted as follows.

In addition, the symbols of the equivalent circuit used in Figure 4 are shown in Table 1 below.

First, when the switch transitions from on to off, ignoring the snubber circuit, the voltage V _CE across the switch can be expressed as follows.

At this time, since the input current I _F of the brake chopper device is continuous, the current increases toward the braking resistor as the current decreases as the IGBT is turned off.

Therefore, the voltage variation is expressed as follows.

And, when the IGBT is off, most of the current still flows to the IGBT side. That is, since I _F = i _c , the first term on the right side of Equation (2) is zero.

Therefore, in Eq. (1), the first and second terms on the right side are zero, so the voltage across IGBT V _CE is

It can be seen that it depends on the stray (parasitic) inductance value existing between the braking resistor and the IGBT. However, the magnitude of V _CE is not large because the variation of di _c is not large.

Looking at the moment when the IGBT is about 50% off, the braking resistor current and the IGBT current can be assumed to be I _F / 2 because the current I _F cannot change suddenly.

In this case, V _CE increases the voltage mainly due to the inductance component inside the braking resistor.

For example, assuming that L _SZ = 10uH, L _σ = 2uH, dt = t _off = 1.5us, di _Z = 340A, di _c = -340A, the maximum value of V _CE is

This results in a fairly high V _CE voltage.

Finally, looking at the conditions when the IGBT is off 100%, I _C = 0, I _F = I _Z, so the result of equation (1) is as follows.

According to the equivalent circuit analysis, it is very important to design the inductance included in the braking resistor to minimize the spike voltage generated when the switch is off. Next, the inductance component is shortened by shortening the length between the braking resistor and the IGBT. It is necessary to make it smaller.

On the other hand, the snubber circuit can only offset the parasitic inductance components by designing sufficient capacitance components. In this case, the snubber circuit should be designed so that the magnitude of the discharge resistance is also large enough.

To this end, the snubber circuit is an R-C-D snubber circuit, it is preferable to apply an off snubber.

That is, the overvoltage limiting snubber circuit is a kind of off snubber circuit that limits the Ldi / dt overvoltage generated when the switch is turned off due to the parasitic inductance included in the circuit.

Assuming that the snubber circuit has been removed in FIG. 4, the voltage / current waveform at the time of switching off will be a waveform as shown in [Reference Drawing] (a).

On the other hand, in the case of a circuit with a snubber circuit, as shown in [b] (b), the energy of the parasitic inductance moves to the snubber capacitor, and the spike voltage is limited. Will be discharged.

[Reference Drawing]

At this time, the appropriate variable value of the snubber circuit is obtained as follows.

First, assuming that the magnitude of the variable voltage generated across the switch is ΔV _CE and the voltage of the snubber capacitor ΔV _C = ΔV _CE when the switch is off, the energy stored in the parasitic inductance is expressed as follows according to the energy conservation law. Is possible.

Equation (6) means that the size of the switch voltage ΔV _CE can be controlled using an appropriate snubber capacitor.

The magnitude of the voltage generated by the parasitic inductance when there is no snubber circuit is as follows.

Here, V _d means the magnitude of the input voltage in the steady state. The size of the snubber capacitor for limiting the magnitude of the variable voltage to 10% or less of the steady state can be obtained from Equation (6) as follows.

In addition, the energy stored in the snubber capacitor must be discharged again in the on section of the switch through the snubber resistor R _S.

In order to ensure sufficient discharge, the discharge time Ts is obtained as follows.

The appropriate snubber resistance value obtained from equation (11) is as follows.

In order to confirm the characteristics of the chopper device according to the present invention, a simulation was performed based on the equivalent circuit shown in FIG. 4.

At this time, the simulation tool used PSpice which is generally used in the analysis of electrical and electronic circuits.

In order to verify the effectiveness of the snubber circuit, a comparison was made between the absence of the snubber circuit and the absence of the snubber circuit, and the feedback control was performed at an initial operating condition of 680A.

As a result of the simulation, when the snubber circuit is not used as shown in FIGS. 5A and 5B (FIG. 5A), it can be seen that the voltage across the switch is more than 4500 V. However, in FIG. 5B using the appropriate snubber circuit, the voltage across the switch is shown. There was no spike in it. Instead, it can be seen that all of the instantaneous energy is stored in the snubber capacitor, and the stored energy is gradually discharged through the resistance during the on period of the switch.

Finally, the heat pipe type forced air cooling method of the chopper device according to the present invention should have the following design conditions.

That is, as in the equivalent circuit analysis, the loss of the main circuit element was analyzed for the load parallel chopper device operating as a current source.

For example, a modified circuit for thermal analysis of the equivalent circuit of FIG. 4 was prepared as shown in FIG. 6, and for convenience of calculation, the second loss induced in L and C was ignored, and the conditions are as follows.

(a) The chopper unit and the load are connected in parallel to the current source.

(b) The chopper circuit is only connected during braking and regenerative control of the propulsion control system and is otherwise disconnected from the main circuit.

(c) The losses incurred during switch operation are limited to static losses and switching losses.

(d) Static losses consist only of conduction losses (P _fw ) and switching losses consist of turn on losses (P _on ) and turn off losses (P _off ).

(e) Design not to exceed the temperature T _j = 125 ° C of the semiconductor junction.

In addition, symbols of the equivalent circuit used in FIG. 6 are shown in Table 2 below.

Under these conditions, losses can be obtained through the following process.

First, the conduction loss of the IGBT is obtained. D is gradually decreased from 1 and closes to 0 due to the operation characteristic. Therefore, when the average duty is assumed to be 0.5, the conduction loss of IGBT is as follows.

Then, the conduction loss of the diode Diode is obtained as follows. At this time, since the current flowing back to the diode side does not occur due to the characteristics of the braking circuit condition, the conduction loss of the diode is ignored.

In addition, the voltage across the IGBT at turn-on is equal to the voltage across the braking resistor.

Therefore, the turn-on loss of the IGBT is obtained as follows.

Similarly, the turn-off loss is

The reverse recovery loss of the diode is obtained as follows.

The sum of all the losses found above yields the time-averaged total loss of the IGBT.

As described above, the chopper device according to the present invention can greatly improve reliability by simply configuring two main power IGBTs using two large power IGBTs instead of about ten power devices including the existing two series GTO devices. have.

In addition, in the existing system, a vacuum cooling system is constructed using a cylindrical deposition tank filled with liquid refrigerant, but the maintenance and maintenance can be greatly reduced due to the considerable cost and equipment required for disassembly and reassembly.

In addition, the present invention not only improves maintainability by adopting a forced pipe type of heat pipe type, but also lowers the loss in terms of loss in comparison with the existing system, thereby preventing deterioration of the device and preventing long life. It can be realized.

100: IGBT 110: load resistance (braking resistance)
120: flyback diode 200: snubber capacitor
210: snubber diode 220: snubber resistor

Claims (4)

A brake chopper device for a high speed railway propulsion control system;
At least one Insulated Gate Bipolar Transistor (IGBT) 100 connected in parallel with the load resistor 110;
And a snubber circuit (200) of an off snubber type connected in parallel to the IGBT (100) to limit overvoltage.
The method according to claim 1;
The snubber circuit 200 is a brake chopper device of a high speed railway propulsion control system, characterized in that the snubber capacitor 210, the snubber diode 220 and the snubber resistor 230.
The method of claim 2,
The snubber circuit 200 is connected in parallel with a reflux diode 120 connecting the collector C and the emitter E of the IGBT 100, and the snubber diode 220 and a snubber resistor ( 230 is a brake chopper device of the GT high-speed railway propulsion control system, characterized in that connected in parallel to the snubber capacitor (210).
The method according to any one of claims 1 to 3
The snubber circuit (200) is a braking chopper device of the high speed railway propulsion control system of the GT high-speed railway, characterized in that the cooling by heat pipe type forced air cooling (steel providing cooling).

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