RU99394U1 - AC ELECTRIC POWER SUPPLY SYSTEM - Google Patents

Abstract

1. The system of traction power supply of an alternating current electric locomotive, containing a traction transformer and a rectifier-inverter converter supplying the traction load, characterized in that it contains an active harmonic conditioner connected in parallel to the primary winding of the traction transformer, containing series-connected resistance R, inductance L, capacitance C and a generator current harmonics in the form of a chain of several series-connected single-phase bridge voltage inverters on IGBT modules, a processor device configured to control inverters to form at the output connected to a passive RLC circuit, width-modulated voltages that create counter-directed current harmonics in this circuit harmonics of the primary winding of the traction transformer. ! 2. The system according to claim 1, characterized in that the single-phase bridge voltage inverters are connected in series and are three-level. ! 3. The system according to claim 1, characterized in that the processor device contains current sensors for the locomotive TA1 and the active harmonic conditioner TA2, a voltage sensor for one of the traction transformer windings, voltage sensors on capacitors feeding the inverters from the DC side, a current harmonic filter that emits higher harmonics from current sensor signals. ! 4. The system according to claim 3, characterized in that the current harmonic filter is made in the form of an analog or digital notch filter. ! 5. The system according to claim 3, characterized in that the current harmonic filter is made in the form of a digital low-frequency filter having a cutoff frequency between the first and third harmonics, in series �

Description

The utility model relates to the field of electrified railways and can be used to compensate for reactive power and higher harmonics of the current of an electric locomotive, i.e. to improve energy quality.

Known three-phase active electric filter used in autonomous electrical systems of alternating current with powerful non-linear loads to reduce the higher harmonic voltage components and thereby improve the quality of electrical energy (RF patent No. 2121222 C1, IPC: Н04В 3/54, Н03Н 7/01, publ. . 10.27.1998) - an analogue.

A disadvantage of the known solution is that it does not take into account the effect of distortion on the shape of the current curve.

Known active filter for traction power supplied from an air contact network of an alternating current (RF patent No. 2083388 C1, IPC B60L 9/08, publ. 10.07.97) - analogue.

The known device can be located directly inside the EPS (electric locomotive), or at a traction substation. Using this device directly on the EPS allows you to increase the power factor of the traction unit.

The known solution has the following disadvantages:

- the adopted method of measuring higher current harmonics based on spectrum calculation using a discrete fast Fourier transform, and then, after removing the first harmonic from the spectrum, reconstructing a signal containing only higher harmonics is difficult to implement and not fast enough to use this signal in the loop feedback. This method is unsuitable for rapidly changing operating modes of the traction power supply system;

- it is necessary to have additional rectifiers to feed the inverter capacitors on the DC side. Among all the schemes for connecting inverters to a traction transformer proposed in the well-known solution, there is not a single circuit using a series-connected capacitor in the passive circuit, only inductors are offered, which leads to high resistance of this circuit for higher harmonics currents and to the need for correction of higher harmonics signals generated by inverters in side of increase;

- connecting an active harmonic conditioner (ACH) in parallel to one of the low voltage windings of the traction transformer is not feasible due to problems with the power supply of inverters on the DC side. These circuits must have rectifiers with very low internal resistances and are designed for very high currents due to the shunting of these circuits with a low-impedance motor load. Capacitors simply cannot be charged to the desired voltage.

A known traction power supply system for an AC electric locomotive designed to compensate for reactive power and comprising a traction transformer and a rectifier-inverter converter (RF patent No. 56734, IPC: H02J 3/18, published on November 10, 2007) is a prototype.

A disadvantage of the known solution is the low efficiency of reactive power compensation when working on AC electric locomotives.

The technical result, the achievement of which the claimed solution is directed, is to increase the reliability and efficiency of reactive power compensation and higher harmonics of the current of the electric locomotive, and to improve the quality of electricity.

The specified technical result is achieved by the fact that in the traction power supply system of an alternating current electric locomotive containing a traction transformer and a rectifier-inverter converter configured to supply traction load, an active harmonic conditioner is included in parallel with the traction transformer primary winding, containing in series resistance R, inductance L, capacitance C and current harmonic generator in the form of a chain of several series-connected single-phase bridge inverters voltage on IGBT modules, a processor device configured to control inverters to generate pulse-width modulated voltages on the output connected to a passive RLC circuit, creating current harmonics in this circuit that are opposite to the current harmonics of the primary winding of the traction transformer.

The system, characterized in that to reduce the voltage on the IGBT-transistors, single-phase bridge voltage inverters are connected in series and can be made three-level.

The system, characterized in that the processor device, contains current sensors of the AT1 locomotive and the AT2 active air conditioner, voltage sensor of one of the windings of the traction transformer, voltage sensors on the capacitors supplying the inverters from the DC side, a current harmonic filter that extracts higher current signals from the current sensors harmonics, moreover, the current harmonic filter is made in the form of an analog or digital notch filter, or in the form of a digital low-pass filter having a cutoff frequency between the first and third harmonics, in series with it, the digital phase shifter of the main harmonic of the current is up to an angle of 180 degrees, and an adder, to one of the inputs of which a signal from the current sensor is connected, and to the other, a signal of the first harmonic of the current shifted by 180 degrees.

As you know, the traction network as a single-wire line with the return of current through the earth is almost completely asymmetrical. As a result of this, the currents flowing in the traction network of railways, electrified both by the alternating current system and by the constant system, interfere with the air and cable lines of communication, broadcasting, telecontrol, etc., adjacent to it. It is also known that interference in communication lines due to magnetic influence and electromagnetic processes in the traction network is determined by the higher harmonic components of the traction current spectrum. In addition, current harmonics created by non-linear loads can be serious problems for power systems.

Harmonic components are currents with frequencies that are multiples of the main frequency of the power source. Higher harmonics of the current superimposed on the fundamental harmonic lead to distortion of the current shape. In turn, current distortions affect the voltage shape in the power supply system, causing unacceptable effects on system loads.

The principle of operation of an active harmonic conditioner (ACH) is based on the analysis of harmonics of the current of the nonlinear load and generation of the same harmonics of the current into the distribution network, but with the opposite phase. As a result of this, the higher harmonic components of the current are neutralized at the point of connection of the ACG. This means that they do not propagate from the nonlinear load on the network and do not distort the voltage of the primary energy source.

The inventive traction power supply system of alternating current with ACG is shown in Fig.1-6.

Figure 1 presents a schematic diagram of the inventive system, figure 2 is the current of one of the IGBT modules of a three-level inverter, figure 3 is the voltage on the IGBT module, figure 4 is a control signal from the current harmonic processor at pulse inverter modulators, figure 5 - output pulse-width modulated voltage pulses of three series-connected three-level IGBT inverters at a carrier frequency of 20 kHz; figure 6 - voltage at the reactor L (black) and the capacitor C (gray) before and after turning off the control of the inverters at the moment of 0.233 seconds.

The system contains a traction (power) transformer (EPS) 1, a rectifier-inverter converter 2, a passive power RL-C filter for smoothing rectified voltage ripples 3, a current harmonic generator 4, a processor device 9, galvanic isolation 5 and drivers 6. The processor device contains locomotive current sensor 7 (AT1) and active harmonic conditioner current sensor (AT2) 8, voltage sensor of one of the windings of the traction transformer 1, voltage sensors on the capacitors supplying the inverters 4 from the DC side, filter current harmonics, extracting higher harmonics from the current sensor signals, the current harmonic filter being made in the form of an analog or digital notch filter, or as a digital low-pass filter having a cutoff frequency between the first and third harmonics, and a digital main phase harmonic of the current harmonic connected in series with it to an angle of 180 degrees, and an adder, to one of the inputs of which a signal from a current sensor is connected, and to the other, a signal of the first harmonic of the current shifted by 180 degrees.

The inverter’s capacitors are fed on the DC side through inverters and a passive power RLC filter 3, through which the inverters are connected in parallel with the primary winding of the traction transformer 1. Additional rectifiers for supplying the inverters from the DC side are not required. A voltage limiter-regulator on capacitors connected to a voltage sensor of one of the secondary windings of a traction transformer generates the orthogonal component of this signal, which is summed with a certain weighting factor with the control signal of the processor device for higher current harmonics. The total signal is fed to the device for the formation of pulse-width modulated pulses, which are fed through galvanic isolation 5 to the drivers 6 of the inverter bridges. In order to reduce delays in the current harmonic compensation circuit and to reduce the influence of high-frequency inverter voltages on the voltage of the traction network, the carrier frequency of PWM modulation can be increased to 20 kHz. At such a frequency, the harmonics of voltage and current do not penetrate the traction network, and high-frequency voltages occur only at the inductance L. To reduce voltages and reduce the requirements for the level of insulation, the inductance L is made in the form of several series-connected sections. The RLC circuit, which is part of the ACG, is capacitive in nature at the fundamental frequency and serves to partially compensate the reactive component of the current of the electric locomotive.

An example of a specific implementation.

The applicant conducted studies of the inventive system with the following parameters: Rectifier load current 45 A, power transformer 6 / 0.4 kV distribution substation IrGUPS; isolation transformer 380/220 V (S = 1,5 kVA); inverter power rectifier; rectification voltage ripple smoothing filter (Rf = 50 m, Sf = 10 μF, electrolytic capacitor); Texas Instruments digital signal processor; an inverter based on IGBT transistors (IGBT transistors for current 100-150 A); filter connecting the inverter to the passive RLC circuit (Rf = 1 Ohm, Cf = 10 μF, LC circuit (L = 2 mH, C = 500 μF); inductance at the input of the rectifier (La = 1 mH); single-phase bridge rectifier (Ud = 250 V, Id = 45 A); rectifying load (Ld = 32 mH, Rd = 4 Ohms).

The inventive traction power supply system with ACG current reduces the non-sinusoidality of current and voltage, i.e. improves the quality of electricity. By the distortion coefficient of the sinusoidality of the voltage curve by average values three times, by the maximum values five times; reduction of current non-sinusoidality along the 3rd harmonic component in the same multiplicity; the non-sinusoidality of the current in the lower order of harmonics is also significantly reduced. In particular, the distortion coefficient of the sinusoidality of the current curve when using passive filters was Ki = 25.9%, the distortion coefficient of the sinusoidality of the current curve in accordance with the claimed solution decreased to Ki = 18.5%.

Claims (5)

1. The traction power supply system of an alternating current electric locomotive comprising a traction transformer and a rectifier-inverter converter supplying a traction load, characterized in that it comprises an active harmonic conditioner connected in parallel with the primary winding of the traction transformer, comprising a series resistance R, inductance L, capacitance C and a generator current harmonics in the form of a chain of several series-connected single-phase bridge voltage inverters on IGBT modules, a processor device GUT configured to control inverter for generating at the output, connected to the passive RLC-circuit a pulse-modulated voltage generating circuit in the harmonic current, harmonic current oppositely directed traction transformer primary winding. 2. The system according to claim 1, characterized in that the single-phase bridge voltage inverters are connected in series and are made three-level. 3. The system according to claim 1, characterized in that the processor device contains current sensors of the TA1 locomotive and active harmonic conditioner TA2, a voltage sensor of one of the windings of the traction transformer, voltage sensors on the capacitors supplying the inverters from the DC side, a current harmonic filter emitting from the signals of the current sensors higher harmonics. 4. The system according to claim 3, characterized in that the current harmonic filter is made in the form of an analog or digital notch filter. 5. The system according to claim 3, characterized in that the current harmonic filter is made in the form of a digital low-pass filter having a cutoff frequency between the first and third harmonics, a digital phase shifter of the main current harmonic connected to it up to an angle of 180 °, and an adder in series with one of the inputs of which the signal from the current sensor is connected to, and the signal of the first harmonic of the current shifted by 180 ° to the other.