Autonomous Voltage Inverter Research Articles

Analysis of optimal operating modes of the induction traction drives for establishing a control algorithm over a semiconductor transducer

The study addresses determining optimal operating modes of the induction traction drive. We identified optimal operating modes of the autonomous voltage inverter at different temperatures of windings of the traction motors for a tram carriage and a diesel locomotive.The identification is carried out of optimal parameters in the operating modes of autonomous voltage inverter of the traction drive of a tram and a diesel locomotive. We obtained dependences of performance efficiency and electromagnetic torque of the induction traction motor on the rotation frequency and temperature of the windings for the following modes: acceleration, recuperative braking, and maintaining preset speed.We determined operating modes of induction traction drive of the tram Tatra T3 VPA and the diesel locomotive 2TE25A over the entire range of motors' rotation frequency at spatial-vector and one-time pulse-width modulation of the semiconductor inverter for different values of temperature of the motor's windings. A technique was devised for this purpose, which is based on solving a problem on the optimization of parameters of the traction drive using a combined method that employs genetic algorithms and the Nelder–Mead method.It was established that dependences of change in the transition point from the spatial-vector to the one-time PWM on the temperature of traction motor for a tram and a diesel locomotive are not similar. Different level of the location of this point is predetermined by the different load in magnetic circle of the motor, by different level of saturation coefficient. The difference in saturation coefficient is 0.15‒0.4 r.u.

Управляемая вибрация звеньев подвижности производственного механизма

Introduction. The work subject is investigating friction characteristics of the moving surfaces of the production mechanism (PM) links including executive mechanisms (EM), and work tools (WT) of technological machines (TM) in the low-speed zone of an asynchronous motor (AM) powered from an autonomous voltage inverter (AVI) in the “AVI - AM” system. The work objective is to find a technical solution to the reduction of the friction effect in the PM links on the frequency-controlled drive (FCD) mechanical characteristics in the low- and creep-speed zone, and also, to the validation of the rated vibration feasibility of the mobile links in the PM guides under the starting-braking AM modes. Materials and Methods. To solve the research problems, the concept of bimodal AVI control that provides the formation of quasi-sinusoidal voltage for AM power supply in the “AVI - AM” system with the harmonic coefficients K u u > 8% is used. The program control of the amplitudes of the fundamental 5th and 7th harmonics of the stator current is applied. These harmonics form the fluctuating torques on the AM shaft and cause the normalized vibration of the PM links. Research Results. The justification and experimental proof of the AVI control feasibility providing a project change in the AM shaft vibration amplitude and a decrease in the effective friction coefficient of the PM moving links aiming at the elimination of the seizure of the links under the PM operation conditions are obtained. Such an effect is possible under the AM rotor spinning in the low current frequency (0.5-20 Hz) zone which is typical for the slow-speed motion of PM under the starting-braking FCD modes. Discussion and Conclusions. The application domain of the developed technical solution covers many PMs with FCD for which the short-time operation modes (with CY of 40% and more) are considered basic. Thus, the use of the effect of vibration linearization of the friction coefficient in the PM links allows the following: to reduce the AM breakaway voltage and significantly extend the FCD speed control range, to increase the ride quality and improve the PM out put link kinematics on which the WT is fixed.

МАТЕМАТИЧНЕ МОДЕЛЮВАННЯ ПРОЦЕСІВ В ЕЛЕКТРОПРИВОДІ ВОДЯНОГО НАСОСА З АКУМУЛЯТОРНИМИ БАТАРЕЯМИ

Розглядається схема електроживлення електроприводу водяного насоса підвищувача тиску води системи внутрішнього протипожежного водопроводу від резервного джерела з акумуляторними батареями і автономними інверторами напруги, її математична модель та результати моделювання електромагнітних і електромеханічних процесів в двигуні під час пуску і роботи насоса у випадку відсутності основного електроживлення від мережі, що забезпечує використання внутрішнього протипожежного водопроводу при надзвичайних ситуаціях протягом розрахункового часу. Така резервна система може використовуватись також для підтримки неперервності технологічних процесів.
 Загальна математична модель електроприводу формувалась з математичних моделей окремих елементів схеми, які представлені багатополюсниками, а процеси в них описуються замкненою системою рівнянь, – диференційних, алгебраїчних та логічних. Розрахункову схему моделі електроприводу сформовано шляхом з’єднання між собою зовнішніх віток окремих елементів-багатополюсників, а саме: джерела живлення з акумуляторною батареєю, інверторів напруги(катодні та анодні вентильні групи), трансформаторів та асинхронного двигуна. Спосіб з’єднання між собою зовнішніх віток багатополюсників математично описується матрицями з’єднань, які складаються для кожного елемента за принципом: кількість рядків матриці рівна кількості незалежних вузлів схеми, а кількість стовпців рівна кількості зовнішніх віток елемента. Обчислення реалізовано мовою FORTRAN. Загальні підпрограми призначені для виконання математичних операцій над матрицями; чисельного інтегрування систем диференційних рівнянь методом Рунге-Кутта 2-го порядку; розв’язування систем алгебраїчних рівнянь методом Гауса; визначення моментів природного закривання вентилів. Отримано результати моделювання при прямому пуску асинхронного двигуна від мережі, встановлено струм статора; кутову швидкість обертання ротора та електромагнітний момент і момент навантаження. Результати обчислень підтверджені даними експериментальних досліджень, практично співпадають криві струму і напруги живлення асинхронного двигуна від мережі і автономного джерела з акумуляторною батареєю при пуску і роботі насоса, форма вихідної напруги джерела і тиску насоса, впродовж тривалої роботи електроприводу насоса.

Improving the energy performance of an ac electric locomotive using a new compensator control structure

A device for improving the power factor for ac electric locomotives that are based on an adjustable passive reactive-power compensator is described. This compensator configuration allows an increase in the power factor of an electric locomotive in all its operating modes. The control of the compensator unit is based on the method of extremal voltage control at the output of an autonomous voltage inverter (AVI). The voltage is chosen on the basis of the numerical differentiation of the dependence of the power factor on the AVI voltage. The mathematical simulation of the operation of the compensator with an extremal regulator, which was performed in the MATLAB package, showed that the proposed device is highly efficient.

Features of traction electric equipment of prospective electric rolling stock

On the main railways in Russia, two types of current in the contact wire are used: dc voltage of 3 kV and ac voltage of 25 kV with a frequency of 50 Hz. Therefore, prospective electric rolling stock should have double the power. Improving the capacity and structural speed of locomotives is based on the use of asynchronous traction motors (ATDs) with a squirrel-cage rotor allowing increasing the tractive force and the weight of the train and the capacity and speed of cargo delivery, increasing reliability and reducing life cycle costs, and increasing service life. Electrical equipment for such rolling stock should be used when working from either contact system, dc or ac. In this article, the scheme of power circuits is considered using the example of a module of a traction drive in one bogie of dual-system electric locomotives. It is proposed to use the secondary winding of the traction transformer as a choke of the input filter when powered from a dc contact system. Regulation of operation modes of asynchronous traction motors is carried out from static semiconductor converters with a two-tier structure. Input transducers provide the exchange of electric energy between the contact system and the intermediate link of dc voltage, and the output converters regulate the traction motors by changing the magnitude and frequency of voltage on the stator windings of ATD depending on the speed of the locomotive and its operating mode. 4QS input converters and output converters are autonomous voltage inverters of the intermediate ac: in the case of single-phase input and output, they are three-phase. The basic ratios are given to determine voltages and currents of 4QS converters, to determine the variable component of a rectified current 4QS converter, and to formulate requirements for a resonant L2C2 filter configured for a frequency of 100 Hz. Expressions are given for determining the ratio of the input power of the converter, as well as recommendations for determining the basic parameters of electrical equipment.

Construction and modelling energy saving stand on the basis of the asynchronous generator for testing of internal combustion engines

The problem of energy efficiency testing process of internal combustion engines, as well as ways of modernization of testing equipment for internal combustion engines is considered in this paper. The proposed installation of the load for the internal combustion engines, where a braking device is an asynchronous machine with wound rotor and connected to the rotor of the asynchronous machine autonomous voltage inverter has been considered. This setting provides the energy transfer to the grid obtained from the stator and phase rotor of asynchronous generator. The synthesis of the asynchronous machine control system and independent voltage converter, which allow control the internal combustion engine load, regardless of the shaft speed and reactive power network has been performed. Synthesized control system allows compensate the reactive power in the network, regardless of the stand operation mode. A computer model of the entire test stand control system is performed. A computer simulation of the internal combustion engine test station in such modes, as maintenance of constant torque and maintenance of the constant internal combustion engine rotation speed is carried. The energy data of test stand for an internal combustion engine are obtained. Disadvantages of the test stand design are found and analyzed

Research and development of conversion of direct current voltage to the quasi-sinusoidal voltage with pulse-width modulation

Practically all widely used variable-frequency alternating-current electric drives with autonomous voltage inverters (AVIs) use pulse-width modulation (PWM) according to one of the following techniques: sinusoidal, space-vector, and relay. Fulfilling the relay PWM requires an analog–digital converter (ADC) with high resolution and sample rate. Vector PWM has a nonsinusoidal output voltage that causes additional losses in the motor. The main problem of a symmetrical (centered) sinusoidal PWM is underuse of a dc link. For a long time, the vector PWM method was taken to be most promising one due to the absence of this defect. In practice, this technique is applied in areas without a strong voltage criterion, for which reason it has limited use. Moreover, due to another significant problem, which is the “dead” time on the sector borders at the vector PWM, different modified methods for constructing the sinusoidal PWM have become widespread, especially in modern asynchronous motor control systems, with the development of digital microprocessor systems. To determine the quality of different types of PWMs, a complex model of an electric drive, incorporating an inverter control system that implements different algorithms of constructing the discrete PWM signals is developed. The model and the electric circuit are constructed in LabVIEW and NI Multisim, respectively. The obtained simulation data can be used to select the optimal method of controlling the AVI. The analysis that has been conducted allows one to select an optimal PFWM control strategy in terms of research results concerning electric power quality and mechanical properties.

Braking mode simulation of induction motor of variable-frequency drive using stator current harmonics **

The work objective is to study electrodynamic processes in the frequency-controlled drive (FCD) by the mathematical modeling method, in particular, in the two-current mode of the dynamic braking considering the 5th and 7th current harmonics of the induction motor (IM) stator. The features of forming IM stator current low frequencies (0.2-15 Hz) by the autonomous voltage inverter (AVI) followed by the additional electricity loss in the FCD, and the appearance of torque ripple on the IM shaft causing jerkiness of the actuating mechanism (AM) of the production machine (PM) executive device (ED) in the low speed zone and complicating their locating in the prearranged position, are given. It is hard to implement the FCD scheduled deceleration without trajectory correction at the friction forces ambiguity in the ED AM mobility links and availability of the torque ripple on the IM shaft. To solve this problem, the authors offer, first, to use a spatial-vector pulse-width modulation (SV PWM) with m-fold submodulation of the carrier frequency (CF) and without submodulation in the IM braking mode. Secondly, it is reasonable to apply (momentarily in a low speed area) the principle of linearization by oscillation to reduce the K friction coefficient to a decreased value in the ED AM mobility links by the IM rotor microvibration due to the 5th and 7th harmonics of the stator current. Thus, the work on modeling FCD (in Matlab + Simulink software package) allows more accurately define the impact of the 5th and 7th harmonics of the IM stator current on the capability of the software implementation of the two-current mode of the FCD dynamic braking while reducing the total energy loss in the ED AM low-speed motion area. In addition, the applicability of the proposed solutions of the electric drives of mechatronic and robotic multipurpose systems with higher requirements for positioning in the basic AM - AVI circuits is confirmed.

Determination of Energy Loss in Power Voltage Inverters for Power Supply of Locomotive Traction Motors

The present work aims to research for power loss in electric power converters of locomotives. In locomotives with induction motors is apply autonomous voltage inverter that operates with high frequency switching. This produce large power losses, which reduce the overall efficiency of locomotive. The exact definition of these power losses allow more accurately determine the energy efficiency of the power inverters.

Increase in the Power Factor of the Electric ac Loco-motive due to a New Structure of Compensator Operation

The paper presents a device developed on the basis of the adjustable passive reactive power compensator and intended for the increase in the power factor of the electric AC locomotive. Such configuration contributes to the increase in the power factor of a locomotive in its all working modes of operation due to approximation of its power factor value to the maximum possible values. The compensator is operated by the method of extreme voltage control of autonomous voltage inverter. Mathematical modeling of work of an electric locomotive equipped with such compensator was performed with MATLAB package and showed a possibility of increase in the power factor up to 0.98.

Losses of power in asynchronous traction engines of prospective electric rolling stock

Powered by autonomous voltage inverters, asynchronous traction engines of prospective electric rolling stock show signs of deterioration in current and voltage, which decreases the efficiency and power factors of these engines compared with corresponding indicators for engines powered by sine voltage power generators. As a result of harmonic analysis of curves of output voltage and current of two-level autonomous voltage inverters with amplitude pulse-width output voltage modulation, performed in the MatLab/Simulink and Mathcad software package, it was found out that the use of pulse-width modulation of autonomous inverter output voltage in a DTA-1200A prospective asynchronous traction engine leads to only a minor impairment of its energy indicators. At the same time, the use of multilevel autonomous voltage inverters, which require more complex and expensive converter electric equipment, is currently hardly justified.

Методы широтно-импульсной модуляции мощных активных выпрямителей при несимметрии напряжения

Powerful main electric drive rolling mills are made, usually multi pulses using synchronous motor and frequency converters, consisting of active rectifier and autonomous voltage inverter. Such schemes allow the use of PWM techniques that provide low frequency switching power switches acceptable harmonic structure of the network current transformers and voltage at the point of common coupling. This is due to the property of three-phase systems, ensuring the absence of harmonic multiples of three. These properties are valid only if the symmetry of voltage, so unbalanced currents appear in all odd harmonic spectrum and the application of a low switching frequency becomes invalid. The article presents the results of a study on the mathematical model of the main drive of a cold rolling mill 2000 different methods of PWM in balanced and unbalanced modes. Methods PWM five switchings per quarter period (removing 11, 13, 23, 25 harmonics), with nine switching quarter period (removing 3, 5, 7, 9, 11, 13 harmonics), a method of switching the PWM a quarter of the period and the classical method of PWM. In symmetric modes of the most effective method SHE PWM with five switching quarter period. When the supply voltage unbalance similar results give the classic method of PWM and SHE PWM method with nine switching quarter period. The application of these methods in single-ended modes rather than the other.

Static and dynamic characteristics of antiparallel diode as part of switching power module

A numerical simulation of the operation of a fast antiparallel diode in the switching power module of an autonomous voltage inverter is carried out. The time of turning off the transient and the static and transient heat losses in the diode are calculated as a function of the electrophysical parameters of the semiconductor diode structure.