RU2710022C1 - Switching filter compensating unit - Google Patents

Abstract

FIELD: power supply system.

SUBSTANCE: invention relates to power supply systems of AC electric railways, in particular to devices for compensation of reactive power of traction load and filtration of higher harmonics of current and voltage in traction network, i.e. to filter compensating units (FCU). Disclosed is an additional reactor, voltage and current sensors and a control unit, which reduced current and voltage surges when switching FCU sections. Damping resistor is switched on during section switching. Damping resistor is bypassed in commutation at current passing through zero.

EFFECT: technical result consists in reduction of electric energy losses, id est energy saving, without damage to the transportation process when passing heavy-weight compounds by changing the value of FCU capacity.

1 cl, 1 dwg

Description

The invention relates to power supply systems for electric railways of alternating current, in particular, to devices for transverse capacitive compensation of reactive power of the traction load and filtering higher harmonics of current and voltage in the traction network, that is, filter-compensating installations (PKU).

PKUs are known that are connected between a supply contact wire or a 27.5 kV supply bus and a zero rail rail, containing a capacitor and a reactor connected in series, forming an LC circuit, tuned to filter the third harmonic component [1,2]. The principle of operation and explanations to the PKU scheme in the traction network are given in [1,2]. To limit inrush currents and overvoltages on the capacitor when switching on the FKU, a damping (starting) resistor is switched on in series in the LC circuit for the duration of the switching, which after switching on the FKU is shunted by a switch.

The disadvantage of these analogues is that the traction load on the inter-substation zone is constantly changing, while the value of the PKU capacity remains constant regardless of the load. The value of the PKU capacity according to existing regulatory documents is selected on the basis of obtaining the minimum loss of electricity or on the basis of the maximum possible increase in voltage to ensure the carrying capacity of the railway. In the second case, the capacity is approximately 1.5 times greater than in the first case. This means that if you select the capacity according to the first option to obtain minimal losses at medium loads, then this capacity is not enough to maintain the voltage during the passage of heavy trains. If you select a capacity such as to allow heavy trains to pass, then at moderate loads there will be overcompensation of reactive power, and at the same time voltage and energy losses can increase excessively. In this case, an emergency shutdown of the PKU may occur. In addition, at high voltage, the reliability of the capacitors decreases sharply. Consequently, the PKU must be adjustable and have at least two values for the above modes to ensure a reduction in energy losses, i.e. energy saving without prejudice to the transportation process when skipping heavy trains by changing the PKU capacity value.

Also known is a device for automatically controlling reactive power compensation, which has two power levels [3]. The disadvantage of this device is that when shunting one section of the device in the remaining section, surges and currents occur.

As the closest technical solution, we take a switched filter-compensating installation described in [4]. The presence of two sections in the capacitor bank provides two levels of power PKU - the smallest and largest.

The disadvantage of the prototype is that the steps of the FCCC at the same reactor inductance and different capacitance values have different resonant frequencies, which affects the filtering properties of the device. In addition, with an increase in the power of the PKU, i.e. when bypassing one section of the capacitor bank in the remaining LC circuit, there is no damping resistor, which causes significant inrush currents and overvoltages on the remaining capacitor.

The purpose of the invention is to increase the efficiency of the device, reduce the inrush current and voltage on the capacitor sections when switching to high power and thereby increase the operational reliability of the FCU and its durability.

This goal is achieved due to the fact that a damping resistor shunted by the second switch is connected to the switchable filter-compensating device containing the first switch connected by the first terminal to the supply bus and the second terminal through the reactor to the first terminal of the capacitor bank with two series-connected sections connected by the first terminal to the junction point of two sections of the capacitor bank, a second reactor is additionally introduced, connected between the second terminal of the condensate battery and the first output of the damping resistor, a current sensor connected between the second output of the damping resistor and the zero bus напряжения a voltage sensor connected between the supply bus and the zero bus and a control unit with two inputs and two outputs, the first input of the control unit is connected to the voltage sensor, and the second input is to the current sensor, the outputs of the control unit are connected to the control inputs of the second and third switch¸ and the second output of the third switch is connected to the first output of the damping resistor. In addition, a bipolar thyristor switch is used as the second switch.

The proposed device has two main distinguishing features from analogue [3] and prototype [4]. Firstly, when bypassing one section of the capacitor bank in series with the remaining section in order to limit overvoltages and overcurrents, a damping resistor is turned on. Secondly, for the same purpose, the damping resistor after the closure of one section is bridged with a bipolar thyristor key at the moment the current passes through zero.

In fig. 1 shows a diagram of the invention, which adopted the following notation:

1 - supply bus 27.5 kV,

2 - the first switch

3 - the first reactor

4 and 5 - the first and second sections of the capacitor bank,

6 - capacitor bank,

7 - connection point of the first and second sections of the capacitor bank

8 - the second reactor

9 - the third switch

10 - damping resistor,

11 - the second switch

12 - current sensor,

13 - zero tire - rail,

14 - control unit.

15 - voltage sensor.

The scheme works as follows. Before turning on the first - the main switch 2, which puts the device into operation, the switches 9 and 11 open. The switch 2 is turned on and the device with two series-connected capacitor sections is connected to the supply voltage through the damping resistor 10. After several periods of the supply voltage, when the transition process ends, the second switch 11 is turned on and the damping resistor 10 is shunted, the damping resistance becomes equal to zero and the PKU at normal loads operates in normal mode.

When heavy trains pass and the load increases, the voltage in the traction network drops. Having received a voltage reduction signal from the voltage sensor 15, the control unit 14 sends a signal to turn off the switch 11. After the switch 11 is turned off, the switch 9 is turned on. The second section of the FCU (capacitor 5 and reactor 8) is excluded from operation. The capacity of the PKU in this case increases, which provides the necessary increase in voltage in the contact network. After a short period of time, the damping resistor 10 is shunted by the switch 11.

In this case, the resonant frequency of the PKU remains the same, since both sections of the PKU are tuned to the same frequency of 142 Hz to filter the third harmonic with a slight detuning. There is no damping resistor 10 in the circuit of the shunted second section of the FCU 10. However, as the authors showed, no dangerous inrush currents and voltages occur in it. In the prototype, it was necessary to discharge the capacitor of the second section of the FCU necessarily through a damping resistor in order to avoid extracurrents when the capacitor is short-circuited. When a capacitor is discharged through a reactor, hazardous overvoltages and overcurrents do not occur. In a closed circuit there are non-dangerous fluctuations in voltage and current with a frequency of 142 Hz, which due to the small active resistance of the reactor gradually decay. But then, when the second section is bypassed, the damping resistor 10 is turned on in series with the first PKU section. This significantly reduces the inrush current and voltage on the elements of the first section. After several periods of the supply voltage after turning on the switch 9, the switch 11 is turned on, the shunt damping resistor.

Due to the presence of a current sensor 12, the control unit 14 provides a pulse to turn on the switch 11 (bipolar thyristor) at that time ¸ when the installation current passes through zero. This ensures a transient process with minimal excess current and voltage.

When the load in the traction network decreases, to switch the PKU into the normal energy-saving mode, the switch 11, and then the switch 9 are turned off.Then, after some time, the switch 11 is turned on, the shunt damping resistor 10 and the PKU are transferred to the normal energy-saving mode. The voltage across the capacitors decreases and they wear less. Power losses in this mode are minimal.

Before turning off the installation, turn off the switch 11 and the damping resistor 10 is introduced into the circuit of the PKU. After that, the main switch 2 is turned off.

The economic effect of the invention is expressed in increasing the reliability of the device, which allows it to be turned on and off as needed with variable traction load and transfer the device from unregulated to adjustable mode. The latter is relevant for eliminating the generation of reactive power at low traction loads and for increasing the voltage in the contact network at high traction loads.

Sources of information

1 . German L.A., Serebryakov A.S. Adjustable capacitive compensation settings in railway traction power supply systems: monograph. M .: MIIT, 2012 .-- 211 p.

2. Borodulin BM, German L.A., Nikolaev G.A. Condenser installations of electrified railways. - M .: Transport, 1983. - 183 p.

3. Patent No. 2459335 dated 04/22/2011. The device of switched single-phase transverse capacitive compensation (Vasiliev S.N., Goncharenko V.P., Latmanizov M.V., Mizintsev A.V.). Publ. 20.08.2012, Bull. 23.

4. Patent No. 2475912 dated 03/09/2011. Switchable single-phase transverse capacitive compensation (Serebryakov A.S., German L.A., Dulepov D.E., Semenov D.A.). Published on 02.20.2013. Bull. 5.

Claims (2)

1. Switchable filter-compensating installation, containing the first switch connected by the first output to the supply bus, and the second output through the reactor to the first output of the capacitor bank with two series-connected sections, a damping resistor shunted by the second switch, the third switch connected by the first output to the connection point two sections of a capacitor bank, characterized in that a second reactor is introduced, connected between the second terminal of the capacitor bank and the first terminal damped resistor, a current sensor connected between the second output of the damping resistor and the zero bus voltage sensor connected between the supply bus and the zero bus, the control unit with two inputs and two outputs, the first input of the control unit is connected to the voltage sensor, and the second input to the sensor current, the outputs of the control unit are connected to the control inputs of the second and third switches, and the second terminal of the third switch is connected to the first terminal of the damping resistor. 2. The device according to claim 1, characterized in that a bipolar thyristor switch is used as the second switch.

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