RU2370381C1 - Method for increase of energy indicators of ac electric locomotives - Google Patents

Abstract

FIELD: electricity. ^ SUBSTANCE: invention is related to the field of railway transport and is aimed at improvement of single-phase-direct current locomotives, which operate in mode of recuperative braking. Higher energy indicators of single-phase-direct current electric locomotives with rectifier-inverter converters is provided by increase of current inversion into contact circuit in mode of recuperative braking in zone of high speeds of electric locomotive motion through change of transformer transformation ratio in process of recuperation current. It is suggested to realise the method with the help of functional controller, which represents board of electronics installed in control unit of rectifier-inverter converter of electric locomotive, which provides for increase of voltage to maximum permissible level of traction motors operating in generator mode. ^ EFFECT: improved power ratio of electric locomotive. ^ 5 dwg, 3 tbl

Description

The invention is applied to railway transport and relates to a method that improves the energy performance of single-phase DC electric locomotives with rectifier-inverter converters (VIP) by increasing the inversion of current into the contact network in the mode of regenerative braking.

Regenerative braking is a resource-saving mode (inverting electrical energy into a contact network) and is used to maintain or reduce the speed of a train.

VIP is designed to rectify a single-phase alternating current with a frequency of 50 Hz into a constant, continuously regulating the supply voltage of traction motors in traction mode and converting direct current into a single-phase alternating current with a frequency of 50 Hz and smoothly regulating the counter-EMF of the inverter in the mode of regenerative braking [1]. Several VIPs are used on an electric locomotive, depending on its series.

Figure 1 presents a simplified schematic diagram of an electric locomotive in regenerative braking mode. The circuit diagram contains a traction transformer T having a primary winding (U ₁ ) and a secondary winding made in the form of three series-connected sections, two of which are of equal voltage to 315 V (a1-1 and 1-2), and the third to double voltage 630 V (2-x1), and four parallel branches of the VIP, parallel connected between the DC bus (Fig.1). Each branch of the VIP contains a pair of serially connected controlled arms of the thyristors, and their midpoints are connected to the corresponding terminals of the secondary winding of the transformer. The power part of the VIP consists of eight thyristor arms V1, V2, V3, V4, V5, V6, V7, V8, shown in figure 1. To the plus and minus buses of the VIP are connected through a smoothing reactor (1) parallel-connected traction motors of an electric locomotive operating in a generator mode, containing an armature (G1, G2, Gn) and field windings (OB1, OB2, OBn) connected independently to the rectifier excitation unit (WWW), Fig. 1. A block of ballast resistors (BBR) R _{b is} included in each generator circuit.

A known method of regenerative braking used on AC electric locomotives, the method includes four zones for regulating the rectified voltage on the generators, in order to control the speed of the electric locomotive (braking force) by applying control pulses (β is the angle of advance of the opening of the thyristors, α _p is the angle of regulation in phase) on certain shoulders of the VIP control unit of the rectifier-inverter converters (BUVIP) or microprocessor-based motion control and diagnostics system (MASD), and on the fourth zone of voltage regulation, the angle α _{p is} limited to 3.5 zones. Zone-phase regulation of the voltage of the VIP in the regenerative braking mode is presented in table 1 [1].

In order to switch from traction mode to recovery, it is necessary to transfer traction motors to generator operation. To do this, assemble a scheme of independent excitation of the engines. Field windings are connected to a separate field rectifier. In the recovery mode, the current I _d flows in the converter circuit due to the emf generator engine.

During recovery, the configuration of the VIP circuit remains unchanged. Therefore, the current I _d flowing in the motor circuit also coincides with the conductive direction of the VIP valves. The direction of the generator emf of an electric machine coincides with the current I _d flowing through it, which is a sign of an electric energy source.

The secondary transformer winding becomes the energy receiver. For an energy receiver, it is necessary that the voltage and current flowing through the transformer winding have opposite directions. From this it follows that the thyristors of the VIP open in a sequence that ensures the flow of current through the windings of the transformer with a predominantly negative secondary voltage. Under these conditions, the transmission of electric energy from generators G from a direct current circuit to an alternating current network of a contact network is ensured. In the regenerative mode, the VIP operates as a dependent inverter, this process of converting current is called the inversion of electrical energy.

In order to maintain the given braking force, the driver controls the counter-EMF of the VIP in the low and medium speed zone, and in the high speed zone, the excitation current is controlled by the brake lever by means of the WWW.

A block of ballast resistors is included in each generator circuit. BBR are used to equalize the currents of parallel connected traction motors and ensure stable operation of the regenerative braking mode, figure 1 [1].

It is known that the higher the voltage regulation zone of the VIP, the greater the inversion of electrical energy into the contact network generated by the generators. However, in all domestic modern single-phase direct current electric locomotives, in order to prevent overvoltage on the generators, the voltage generated by the secondary winding of the traction transformer and the VIP is limited to 3.5 zones, which amounts to 1180 V at the inverter output. A further increase in the voltage on the generators is impossible. With an increase in the speed of movement, the braking force is regulated, reducing the excitation current from 1000 A to the minimum, the voltage remains unchanged - 3.5 zones (1180 V), although with a decrease in the recovery current, losses in the BBB units also decrease, and the transformation coefficient of the transformer remains unchanged K _t - const. As an example, we give the calculation of the return of current i ₁ to the contact network with a typical control method in the regenerative braking mode. The calculation is carried out for a rated voltage in the contact network of 25 kV.

With the inclusion of a block of ballast resistors in the armature circuit, we determine the voltage drop across the BBB under the action of the recovery current according to the formula

where I _d is the recovery current of TED in generator mode;

R _BBR - active resistance of the block of ballast resistors (BBR-162).

The calculation of the voltage drop is performed for the recovery current I _d = 1000 A

The voltage at the inverter output at a current of 1000 A will be

- напряжение на выходе инвертора.Where

- voltage at the inverter output.

U _and = 1180-143 = 1037 V.

In this case, the transformation ratio of the transformer will be equal to

where U ₁ is the voltage of the primary winding of the traction transformer;

With a further decrease in the recovery current I _d, the transformation coefficient of the transformer K _t will remain constant (const), Fig.2.

Then the current return to the contact network is

At current I _d = 900 A with K _t = const

We will perform a similar calculation for the recovery currents I _d at a value of up to 100 A and return current to the contact network i ₁ , the calculation results are summarized in table 2.

According to the results of the calculation of Table 2, the construction of i ₁ = f (I _d ) of the return of electric energy to the contact network i _{1 was} performed depending on the regulation of the recovery current I _d , with a typical regulation method K _t = const, Fig.3.

The disadvantage of a typical method of regenerative braking is the low energy performance of an electric locomotive. For example, the power factor of an electric locomotive is not more than 0.84 [1].

The aim of the invention is to increase the energy performance of the electric locomotive in regenerative braking mode in the area of high speeds of the electric locomotive by changing the transformation coefficient of the transformer K _t (var - variable) when regulating the recovery current I _d , Fig.2.

The proposed method consists in the fact that when regulating the recuperation current I _d , in the zone of high speeds of the electric locomotive, the transformation coefficient of the transformer K _t = var, which affects the return of current to the contact network, according to formula (4), taking into account the decrease in drop, is additionally changed voltage on the BBR. For example, we give the calculation of the current return to the contact network with the proposed control method in the regenerative braking mode.

The calculation of the voltage drop is performed for a recovery current of 1000 A according to the formula (1)

The inverter voltage at a current of 1000 A is determined by the formula (2)

U _and = 1180-143 = 1037 V.

Define by the formula (3) the transformation ratio of the transformer

We determine by the formula (4) the current return to the contact network

With a decrease in the recovery current I _d , the voltage drop across the BBB also decreases, and therefore, it is possible to carry out a reduction in the transformation coefficient of the transformer.

So, at current I _d = 900 A

стало

. В результате напряжение на выходе инвертора может составлятьGiven the decrease in current, the voltage drop decreased, instead of

has become

. As a result, the voltage at the inverter output can be

U _and = 1180-128.7 = 1051.3 V.

Then the transformation ratio of the transformer will be

The return of current to the contact network will increase

The lower the recovery current, the greater the efficiency of inverting electrical energy into the contact network.

We will perform a similar calculation for the recovery currents I _d at a value of up to 100 A and return current to the contact network i ₁ , the calculation results are summarized in table 3.

According to the results of the calculation of Table 3, the function i ₁ = f (I _d ) of the return of electric energy to the contact network i ₁ is constructed depending on the regulation of the recovery current I _d , with the proposed regulation method K _t = var, Fig. 3.

Based on the calculation of tables 2 and 3, the economic efficiency (%) of the return of electric energy i ₁ (A) to the contact network was constructed with the proposed control method, Fig. 4. According to the calculations (tables 2 and 3), it was found that, on average, when regulating the recovery current from 1000 A to 200 A in the zone of high speeds of the electric locomotive, the savings amounted to 6.34% on average, Fig. 4.

It is proposed to increase the voltage to the maximum permissible level of traction motors operating in the generator mode due to the functional regulator, which is an electronics board 2 installed in the BUVIP of the electric locomotive, Fig. 5.

table 2 Recovery current I _d , A 1000 900 800 700 600 500 400 300 200 one hundred When K _t = const, K _t = 24.108 Return current to the contact network i ₁ , A 41.48 37.33 33.18 29.04 24.88 20.74 16.59 12.44 8.3 4.15

Table 3 Recovery current I _d , A 1000 900 800 700 600 500 400 300 200 one hundred When K _t = var 24,108 23.78 23.46 23.15 22.85 22.55 22.27 21,99 21.71 21.45 Return current to the contact network i ₁ , A 41.48 37.85 34.1 30,2 26.26 22.17 17.96 13.94 9.21 4.66

Literature

1. Electric locomotive VL85. The operation manual [text] / B.A. Tushkanov, N.G. Pushkarev, L.A. Pozdnyakova, etc. - M .: Transport, 1995. - 480 s: ill., Tab.

Claims (1)

A method of increasing the energy performance of single-phase DC electric locomotives in regenerative braking mode, which includes supplying control pulses to the inverter arms with a rectifier-inverter converter control unit or a microprocessor-based motion control and diagnostics system, and in the high-speed driving zone in the fourth voltage regulation zone on the generators , the control angle α _{p is} limited at the level of 3.5 zone, which determines a constant transformation coefficient of transformation torus, characterized in that in the zone of high speeds of the electric locomotive produce a change in the transformation coefficient of the transformer when regulating the recovery current by increasing the voltage to the maximum permissible level of traction motors operating in generator mode, taking into account the reduction in voltage drop across the blocks of ballast resistors by means of a functional regulator, which is electronics board installed in the control unit.

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