The analysis of operating conditions of traction drives of electric locomotives with asynchronous traction motors has been carried out. It was found that during operation in the output converter of an asynchronous motor, defects may occur, which leads to asymmetric modes of its operation. Models of a traction drive of an electric locomotive with asynchronous motors with scalar and vector control of the output converter are proposed, taking into account asymmetric operating modes. As a result of the simulation, the starting characteristics of the traction drive were obtained for various control methods both in normal and emergency modes of the drive. For the drive-in emergency mode, the following cases were investigated: the balance of the converter output voltages and the turn-to-turn circuit of 10% of phase A winding of the motor stator; imbalance of the output voltages of the inverter and an intact motor; imbalance of the output voltages of the converter and interturn short circuit of 10% of phase A winding of the motor stator. Comparison of the simulation results have shown that in emergency modes in the traction drive, the torque ripple on the motor shaft in the drive with vector control is 13% less, and in scalar control, the phase current unbalance coefficient is 22% less. The results of this work can be used to study the influence of the output converter control methods on the energy efficiency indicators of the traction drive of an AC electric locomotive.

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Analysis of Control Methods for the Traction Drive of an Alternating Current Electric Locomotive

This paper deals with the analysis of the operating conditions of traction drives of the electric locomotives with asynchronous traction motors. The process of change of the catenary system voltage was found to have a stochastic character. The method of current controller synthesis based on the Wiener–Hopf equation was proposed to enable efficient performance of the traction drive control system under the condition of the stochastic nature of the catenary system voltage and the presence of interferences, when measuring the stator current values of the tractor motor. Performance simulation of the proposed current controller and the current controller used in the existing vector control systems of the traction drives used in the electric locomotives was implemented. The results of the performance simulation of the proposed current controller were compared with the performance of the current controller in existing vector control systems of the traction drives. The results are applicable to the design of vector control systems of traction drives in electric locomotives and to the study of the influence of performance of electric traction drives in electric locomotives on the quality indicators of the power supplied by the traction power supply system under the actual operating conditions of the locomotive.

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Synthesis of the Current Controller of the Vector Control System for Asynchronous Traction Drive of Electric Locomotives

It is shown that the principle of control and voltage supply of the hybrid DC contactor network is realized by connecting the electronic circuit with one terminal between two counter-actuated power-operated semiconductor devices of the two-way key, which shunts the main contacts of the first pole of the contactor, and the second terminal Luce. As a result, the network voltage is fed to the electronic circuit only for a short period of time (several ms), which is determined by the value of the time flow of the load current through the shunted bidirectional NC under the disconnected load. The features of the process of current flowing from the main contacts to the circuits of switching on and off power controlled devices and the charge of the switching capacitor are determined. It was found that in order to ensure reliable switching in the entire range of switching currents of the contactor, it is necessary that the parameters of the elements of the switching circuit and the charge circuit of the switching capacitor were selected on the condition that the current in the switching circuit of the power NC at the moment of its switching was equal to the current in the charge circuit of the switching capacitor. In this case, the value of this current should not be less than the maximum switching-off current of a fully controlled NC. This makes it possible to reasonably approach the determination of the parameters of the elements, which ensure the secure locking of the two-directional NC. As a result of the studies, it was also shown that the proposed hybrid contactors due to the introduction of voltage control of the network compared to the existing ones have competitiveness enhancing properties. In particular, they increase the reliability of the work, they do not need to supply an additional source of power, they exclude standard drivers, minimize energy consumption. Thus, an exemplary aspect of using the scientific result obtained is the ability to create competitive on-line hybrid DC contactors with a voltage up to 1000 V and currents of 100 ÷ 600 A for alternative energy. Key wordhybrid contactor, main contact elements, two directional semiconductor key, voltage control

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Principles of constructing, calculation methods of direct current hybrid contactors for alternative energy

Now about 98% of shunting locomotives of Ukraine are morally or physically worn-out therefore there is a need for development and probe of new types of traction electric drives for locomotives. New designs of traction drives have to conform to the existing requirements for energy efficiency and environmental safety. The choice of the optimum configuration of transmission becomes complicated existence of a large number of alternative options of realization of all its components. For the solution of objective, the method with the application of the generalized function of desirability of Harrington was used. As the basic structure of traction electric transmission of shunting locomotive the hybrid system with stores of energy which allows increasing efficiency of locomotive considerably is accepted. In research options of execution both diesel-generator installation and the traction electric drive are presented.

Searching of The Optimum Configuration of The Traction Electric Transmission of The Shunting Locomotive

. The paper presents the results of studies of the influence of the quality of power systems on the characteristics of an asynchronous electric motor with a squirrel-cage rotor. During the research, a mathematical model of an induction motor, made in the MATLab software environment, was used. Based on the simulation results, the coefficients of the torque ripple and the phase current unbalance were determined. The results obtained are compared with previous studies of the manifestation of turn-to-turn closures in the phases of the motor stator winding, which also create an asymmetry of the rotating magnetic field.

Investigation of the influence of the quality of the power supply system on the characteristics of an asynchronous motor with a squirrel-cage rotor

An analysis of tasks on improving energy efficiency of electric traction systems reveals the need for the introduction of new technologies, namely modern rolling stock with a traction asynchronous electric drive, as well as traction substations, based on new technologies. To solve this class of problems, we have defined the need for an integrated simulation model of the electric traction system that would ensure a sufficient level of its reliability.This work reports details of algorithms for calculating the parameters in order to develop a simulation model of the integrated electric traction system of an underground rail system, which consists of electricity supply subsystems, electric drive of rolling stock, and mechanical part of the traction transmission.In the programming environment Matlab/Simulink, based on the known, actual and refined, estimation parameters, we developed a simulation model of the system of traction electric supply to an underground rail with a two-way power to two tracks. We have constructed a simulation model of the modern traction electric drive of the underground rail cars with a vector system to control an asynchronous electric drive and a uni-mass mechanical part, capable of taking into consideration the impact of the coefficient of adhesion.We have compared results from the imitational simulation of dynamic processes with oscillograms for the actual operation modes of an underground rail system, which confirmed the adequacy of the model to the examined object. The correspondence between results obtained from simulation is confirmed by the oscillograms from analysis of voltage and current of the contact network, as well as by characteristics of the traction and braking modes of rolling stock.We have simulated processes of work of the power supply system, a nonstationary regime at deterioration of adhesion conditions, and a recuperative braking mode with energy transferred to other trains.Using the developed model of the integrated system of electric traction would contribute to a more detailed study into the mutual influence of elements in the electric traction system. That would make it possible to improve the efficiency of making technical decisions related to meeting safety requirements, preventing the disruptions of normal operation, and bringing down operating costs

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Comprehensive approach to modeling dynamic processes in the system of underground rail electric traction

The analysis of operating conditions of induction traction motors as part of traction electric drives of electric locomotives reported here has revealed that they are powered by autonomous voltage inverters with asymmetric non-sinusoidal voltage. It was established that the induction motor operation may be accompanied by defects caused by the asymmetrical modes of the motor stator. A model of the induction motor has been proposed that takes into consideration changes in the values of mutual inductance of phases and complete inductance of the magnetization circuit due to changes in the geometric dimensions of the winding caused by a certain defect. An algorithm that considers the saturation of the magnetic circuit of the electric motor has been proposed.
This approach to modeling an induction motor is important because if one of the stator's windings is damaged, its geometry changes. This leads to a change in the mutual inductance of phases and the complete inductance of the magnetization circuit. Existing approaches to modeling an induction motor do not make it possible to fully take into consideration these changes.
The result of modeling is the determined starting characteristics for an intact and damaged engine. The comparison of modeling results for an intact engine with specifications has shown that the error in determining the controlled parameters did not exceed 5 %. The modeling results for the damaged engine demonstrated that the nature of change in the controlled parameters did not contradict the results reported by other authors. The discrepancy in determining the degree of change in the controlled parameters did not exceed 10 %. That indicates a high reliability of the modeling results.
The proposed model of an induction electric motor could be used to investigate electromagnetic processes occurring in an electric motor during its operation as part of the traction drive of electric locomotives

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Improving a model of the induction traction motor operation involving non-symmetric stator windings

The study considers switching surges at semiconductor switches of semiconductor devices of the direct current at the time of switching electric circuits; such surges occur due to the energy accumulated in the inductive elements of the mains at the load disconnection. As the cost of power semiconductor devices is determined not only by the voltage that they are able to handle but also by the class of the device that determines the amount of the blocked voltage, an important task is to use special measures to reduce these surges down to levels that are close to the network parameters. The aim of this study was to develop a methodology for calculating the parameters of a regulator of switching surges on the basis of a series of parallel-connected energy-intensive varistors used in semiconductor devices of the direct current. On the basis of studying the transient processes that occur in such surge restrictors of voltage in semiconductor devices of the direct current at load switching, analytical expressions have been developed for calculating the basic parameters of the voltage regulator. As a result, an engineering method has been devised for calculating the parameters of varistor surge regulators in hybrid and contactless semiconductor devices of the direct current at a given level of surge admissible for this class of devices. The research findings facilitate high accuracy at a small amount of time in choosing fully controlled semiconductor devices with regard to the current and voltage when designing modern switching semiconductor apparatus that work with the direct current; this helps solve the basic tasks of planning. The suggested voltage regulator for semiconductor switching apparatus of the direct current effectively limits switching surges in the circuits of power semiconductor devices to below 2.5 U nom . It significantly surpasses such parameters as the dimensions, weight and cost of resistive-capacitive surge limiters previously used in semiconductor contactors. Moreover, it can reduce the class level of fully controlled power semiconductor devices that are used in semiconductor switches of such apparatus.

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Methods of overvoltage limitation in modern dc semiconductor switching apparatus and their calculation

Operating modes of the single-phase 4qs transducer with pulse-width modulation as part of the AC electric rolling stock are investigated. The method is developed for determining the PWM parameters, at which the optimum transducer mode in terms of minimizing the reactive power in the “locomotive-traction network” system is implemented. The features of the developed method are the division of the process of determining the optimum PWM parameters into 2 steps. This allows removing unnecessary blocks from the simulation model and reducing the total simulation time. At the first step, the values of the power factor and current of the DC link in the whole range of coefficients of modulation and shift between the network current and the reference sine-wave signal are determined. Further, from the received data array, pairs of values of the PWM parameters, which ensure the highest power factor of the “electric locomotive-traction network” system are allocated and entered into the table system for setting the PWM parameters. At the second step, the dependences of power loss, and, consequently, both the efficiency and total harmonic distortion of the network current on the transducer clock frequency are determined. The determination of power loss is based on the calculation of the energy dissipated for 1 s on the IGBT transistor and snubber resistor depending on instant values of current through them

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Determination of optimal parameters of the pulse width modulation of the 4qs transducer for electriс rolling stock

The study showed that we can implement the principle of current control of the main circuit of a hybrid DC contactor by introduction of a small-size transformer of current into it. It has two primary windings, the first of which is connected to the first pole in succession with the main contact, the second one ‒ in series with a semiconductor switch, which shunts this contact in opposition to the first, and one secondary power supply. The study determined peculiarities of the processes of current flowing from the circuit of the main contacts, the commutation of a current transformer, the charging of a commutation condenser for locking of a semiconductor switch. The study showed that a magnetic wire conductor of a transformer is saturated and a control circuit is deenergized in a switched-on state. When a contactor is switched off, the charge of a commutation condenser capacitor goes due to a direct current under an action of EMF, which occurs on the secondary winding of a transformer during its re-magnetization in the opposite direction by current flowing in a shunting circuit. At the same time, at the given values of a cross section of a magnetic conductor and capacity of a condenser, a voltage level to which it is charged, does not depend on the number of turns of the secondary winding, but it is proportional to a square root of commutated current. The time of its charge under the same conditions is proportional to the number of turns of the secondary winding. This makes it possible to approach reasonably definition of parameters of elements that provide reliable locking of semiconductor switchers. The study showed that the proposed hybrid contactors, due to introduction of circuit current control, have properties that enhance their competitiveness compared to the existing ones. Specifically, they increased reliability, they do not need a power supply from an additional power source, they exclude standard drivers, they show minimized energy consumption. Thus, the application aspect of a use of the obtained scientific result is the possibility of creation of competitive reliable hybrid DC contactors for voltage up to 1,000 V and currents of 100‒630 A

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Marina Glebova

Papers

Comprehensive approach to modeling dynamic processes in the system of underground rail electric traction

Improving a model of the induction traction motor operation involving non-symmetric stator windings

Methods of overvoltage limitation in modern dc semiconductor switching apparatus and their calculation

Determination of optimal parameters of the pulse width modulation of the 4qs transducer for electriс rolling stock

Development of principles and methods for calculation of direct current hybrid contactors