Improving of the vector control system structure of the active controlled rectifier

The vast majority of electricity is used by industrial facilities in a converted form. At the same time, the use of semiconductor converters to obtain the required load parameters is intensively increasing. Current trends in the development and improvement of semiconductor converters are aimed at energy saving by improving their quality of work and reducing the impact on the power supply, load, and related consumers. Frequency converter with DC insert has become widespread and widely used. Its scheme is mainly based on an uncontrolled diode rectifier and an autonomous voltage inverter. Uncontrolled rectifiers are simple and reliable, but have two main disadvantages: the impossibility to recover electricity to the supply network and distortions of the source current shape. We can get rid of these disadvantages by using an active rectifier made according to the voltage source scheme instead of an uncontrolled rectifier. The operation of an active rectifier significantly depends on the type of its control system structure. This article aims to to improve the structure of the switches control system of the active rectifier scheme – voltage source built using a vector calculation algorithm; creation of a MatLab model of a three-phase active-controlled rectifier operating with a fixed modulation frequency and analysis of the influence of the input inductance value on the quality of its operation. The simulation results confirm that the improved structure of the vector control system proposed by the authors ensures high-quality operation of the active rectifier and electromagnetic compatibility of the frequency converter with the power supply network at the level allowed by the standards; simplification of the representation mathematical apparatus of the generalized vectors of currents and voltages at the construction of a vector control system of the active rectifier – voltage source practically did not influence qualitative indicators of the converter work in any way; a network filter must be used to eliminate the final distortions introduced into the source voltage by an additional nonlinear load.

Operation of propeller motors composed of ship electric propulsion systems with semiconductor converters

The calculations of transient processes in ship electric propulsion systems (EPS) with semiconductor converters (SC) show that when the inverter transistors are locked, overvoltage occurs that may break through the insulation of propeller motors (PM). A feature of this overvoltage is its short duration and large value. Pulsed overvoltage of small duration and the EPS value of dozens or more kilovolts may occur in the circuits of the inverter supplying the PM winding. The main cause of overvoltage is the EPS self-induction resulting from rapid current reduction in circuits with inductances, including in motor windings, when the inverter transistors are locked. The paper presents the results of mathematical modeling of the processes arising when the inverter transistors functioning as part of the frequency converter are locked. The results of the analysis confirmed the possibility of overvoltage on the PM winding, which should be taken into account when designing the EPS and selecting equipment.

Research of processes in a converter with four-zone voltage regulation and electromechanical load

The new mathematical models of the electromagnetic processes is designed in three-phase electric circuit of the semiconductor converters with many-server zoned regulation phases voltages disregarding losses in semiconductor commutator for quick estimation of the influence parameter loads on level and form of the output voltage. mathematical model of the semiconductor converter is also used for study of the connecting processes in semiconductor converter with actively-inductive load. Will develop the method multivariable function, what fall into algorithmic equations of the analysis formed and connecting processes in furcated electric circuit with semiconductor commutator and reactive element, toward account of the particularities of the use phase and linear voltages to network of the power supply. Analysis of the electromagnetic processes is organized beside this article in electric circuit with semiconductor commutator. Mathematical model is created for analysis electro-magnetic processes in semiconductor converter with width pulsed regulation of the output voltage. The broughted graphs, which reflect the electromagnetic processes in electric circuit. Method much parametric functions was used when performing calculation. The mathematical model of the converter is created for eleven zoned regulations of the output voltage. Article is devoted to the development of a method of multi-parametric modulating functions by means of working out of new mathematical models and definition of functions and the algorithmic equations for the analysis on sub-system components of electromagnetic processes in electric circuits of variable structure with sinusoidal, direct and pulsing voltage. Introduction of functions with discrete parameters in the algorithmic equations for analysis of processes in circuits with semiconductor commutators simplifies modeling on subsystem components. The mathematical model of steady-state processes and transients in electric circuits of semiconductor converters of modulation type with multi-channel zonal use of phase and line voltages of a three-phase network of power supplies is developed. The mathematical model of electric circuits of thyristor shapers of electro-discharge pulses for the analysis and the matching of capacitors charging modes with decrease several times of electric resistance of technological load is also created.

THE INFLUENCE OF THE INPUT INDUCTANCE ON THE QUALITATIVE INDICATORS OF ACTIVE CONTROLLED RECTIFIER

The main part of electricity is used by industrial plants in a converted form and the use of semiconductor converters is growing rapidly. The requirements for the quality of semiconductor converters are increased. And their impact on the power supply, load and related consumers is increased too. One of the most popular converters in the segment of low and medium power drives is a frequency converter made on the basis of a three-phase stand-alone voltage inverter. A significant disadvantage of such converters is the use of a diode rectifier at the input of the circuit, which has disadvantages as the inability to recover electricity to the mains in the mode of dynamic braking of an induction motor and significant distortions of the mains current. These disadvantages can be eliminated by using an active rectifier instead of a diode rectifier, which provides a sinusoidal shape of the mains current in phase with the mains voltage and the possibility of bidirectional energy exchange with the load. The efficiency of the active rectifier-voltage source is determined by the selected control algorithm of the circuit switches and the correct task of the inductance of the input choke. A mathematical model of a three-phase active rectifier-voltage source, working with a fixed modulation frequency with a vector algorithm for building a control system and analysis of the influence of the input inductance on the quality of its work was created. From the simulation results it became obvious that the proposed structure of the control system provides stable operation of the converter and acceptable standards for electromagnetic compatibility with the mains at a fixed modulation frequency; the proposed algorithm for calculating the value of the input inductances allows you to correctly select their allowable value, and obtained in the simulation of the dependence allows you to most accurately determine the value of the input inductances on the allowable level of distortion of mains current and supply voltage.

Algorithm for reducing additional losses in asynchronous electric drives in plants with static power regulators

The ways to reduce losses of electrical energy in power supply systems of industrial enterprises containing powerful semiconductor converters and asynchronous motors are considered. The source of additional electric power losses related to subharmonic nature of voltage fluctuations from operation of converters using the principle of frequency-pulse control is determined. The operation algorithm for thyristor switches of semiconductor converters is proposed, that provides reduction of electric power losses in asynchronous motors connected in parallel with powerful converters. The voltage graphs and currents of simulation model in operation modes of converters show the potential to increase energy efficiency of operation of a wide range of industrial objects with asynchronous motors, connected in parallel and having cyclically changing load.

APPLICATION OF THE AVERAGE METHOD FOR ANALYSIS OF DC VOLTAGE CONVERTERS WITH INTERRUPTED CURRENTS IN INDUCTIVE ELEMENTS

The fundamentals of the state-space averaging method using Lagrange's theorems for calculating dc semiconductor converters, which operate in modes of intermittent currents in inductive elements, are considered. To implement the assumption introduced in the study, it is proposed to replace the capacitor in the output circuits of the converter equivalent circuit with a source of constant emf. This makes it possible to obtain a simplified mathematical model of the converter for calculating the integral characteristics, which corresponds to a jointly defined system of algebraic equations with averaged variables. Using the developed models, the parameters of the buck, boost, and inverting converters are calculated, the analytical and graphic dependencies of the limiting values of these parameters are determined, which ensure the specified operating mode. The obtained dependencies make it possible to compare the properties of converters and select their effective parameters. References 10, figures 1, table 1.

MODELING THYRISTOR TRANSDUCERS IN MATLAB ENVIRONMENT TAKING INTO ACCOUNT THE PECULIARITIES OF THEIR IMPLEMENTATION

The authors present the study of synthesis methods for simulating the models of semiconductor rectifiers. Simulation of semiconductor rectifiers is quite studied today, but many authors carry out synthesis in their own unique way. The need to apply high technologies in variable speed drives with the development of mechanisms and working machines is growing, the automated variable speed drive is being introduced increasingly, making the energy substrate for aggregates and working machines. The relevance of this work is explained by the fact that currently developing technologies make it possible to manufacture more advanced semiconductor elements. The more relevant and significant is the study of refined digital models of electric drives containing semiconductor converters. This paper will summarize known approaches to the development of rectifiers’ digital models, as well as it will offer the authors’ own vision of this issue – taking into account as many individual features of semiconductor elements and the entire electric drive system as a whole as possible. The option proposed for consideration differs in that when developing in Matlab environment the parameters of real existing power elements and their digital analogues are consistent. The article also examines the issue of creating a digital model of the electric drive reverse system including a thyristor transducer and an engine; the transition characteristics of the refined model are illustrated. The result of this study is the analysis of different approaches to modeling semiconductor converters in electric drive systems. In this regard, a refined approach to modeling semiconductor rectifiers was considered, consisting of maximizing approximation of the model structure to real implementation, taking into account all elements, included in the structure of the ventilated electric drive. The study suggests that the developed simulation models can be used for the design of a real power converter in the conditions of a production enterprise.