Paweł Szcześniak

Comparison of control methods for a dynamic voltage restorer using a three-phase matrix converter

A dynamic voltage restorer (DVR) is used in a power distribution system to protect sensitive loads against voltage disturbances. The commonly used DVR system contains a converter with direct current (DC) link and energy storage elements. The DC energy storage part of the system is the most expensive element and has a large value. As an alternative, therefore, DVR systems can use alternating current AC/AC converters without DC energy storage. This paper presents the properties of a DVR system based on a direct matrix converter using three control methods: in-phase, pre-sag, and energy-optimal. The paper defines basic mathematical relationships and static characteristics and describes the range of voltage compensation by use of the described compensation methods. Simulation results are obtained and presented in order to verify the correctness of the compensation. The features of such a DVR system configuration are considered in the context of alternative applications for commonly used converters with DC-link energy storage power converters. Application of the matrix converter in electrical power systems is still not very popular, due to limited output voltage and the complex structure and process control. This article is an attempt to show the usefulness of the matrix converter in spite of its limitations and the complexity of the design.

Review of AC–AC Frequency Converters

This chapter concentrates on the reviewing of power frequency converter topologies, exploring of various alternative topologies and comparing of their relative advantages and disadvantages. It provides an outline of the structures and control strategies of power frequency converters. Furthermore, there will be shown the basic operating characteristics of several topologies of PWM AC–AC frequency converters. The major focus is given to the fundamentals of matrix converter.

Control Algorithm Concept for AC Voltage Stabilizer Based on Hybrid Transformer with a Matrix Converter

This paper presents the concept of a control algorithm and a study of its properties for an AC voltage stabilizer based on a three-phase hybrid transformer with matrix converter. Presented in this paper is an approach for obtaining continuous control of the voltage magnitude and phase shift using a conventional transformer with two windings and power electronics devices, referred to as a matrix converter. By adjustment of these voltage parameters we can reduce the effects of overvoltage and voltage sags. The concept of a closed-loop control algorithm and properties of the proposed voltage stabilizers are discussed in this paper.

Hardware realization of an SVM algorithm implemented in FPGAs

The paper proposes a technique of hardware realization of a space vector modulation (SVM) of state function switching in matrix converter (MC), oriented on the implementation in a single field programmable gate array (FPGA). In MC the SVM method is based on the instantaneous space-vector representation of input currents and output voltages. The traditional computation algorithms usually involve digital signal processors (DSPs) which consumes the large number of power transistors (18 transistors and 18 independent PWM outputs) and “non-standard positions of control pulses” during the switching sequence. Recently, hardware implementations become popular since computed operations may be executed much faster and efficient due to nature of the digital devices (especially concurrency). In the paper, we propose a hardware algorithm of SVM computation. In opposite to the existing techniques, the presented solution applies COordinate Rotation DIgital Computer (CORDIC) method to solve the trigonometric operations. Furthermore, adequate arithmetic modules (that is, sub-devices) used for intermediate calculations, such as code converters or proper sectors selectors (for output voltages and input current) are presented in detail. The proposed technique has been implemented as a design described with the use of Verilog hardware description language. The preliminary results of logic implementation oriented on the Xilinx FPGA (particularly, low-cost device from Artix-7 family from Xilinx was used) are also presented.

Modelling and analysis of three-phase hybrid transformer with buck-boost matrix-reactance chopper and active load

This paper deals with a three-phase power system with hybrid transformer (HT). The HT contains a conventional transformer with electromagnetic coupling and PWM AC line chopper integrated with the secondary windings through an electric coupling. The HT uses a three-phase Yy connected transformer with additional secondary windings and three-phase PWM AC line chopper with buck-boost topology. The paper gives a description of the three-phase power system with hybrid transformer (HT) and unsynchronized active load, as well as the mathematical and circuit models of the AC source with HT. The analysis of basic steady state properties of these models are verified by means of the simulation and experimental test results obtained for the power system with HT of about 6 kVA.

Summary of Book

This chapter concerns the summary of this book. The subject of further research and potential applications on matrix-reactance frequency converters are indicated. The practical implementation guidelines for the design of MRFCs are also depicted.

Concept of Matrix-Reactance Frequency Converters

This chapter aims to describe the concept and give a general description of the whole family of three-phase matrix-reactance frequency converters based on the unipolar PWM AC matrix-reactance chopper.

Modelling of Matrix-Reactance Frequency Converters

Matrix-reactance frequency converters are very complex devices, with many elements: semiconductor switches such as IGBTs, and passive elements, such as inductors, capacitors, resistors and integrated control circuits. Their operation is also complex. The analysis and modelling of such converters presents significant challenges, due to their discontinuous switching behaviour. Furthermore, given the increasing number of different modulation strategies it is necessary to study their impact in converter operation. In order to achieve the goal power converters must be appropriately modelled in simulation or analytical studies. Hence, it is necessary to create simple models. In this chapter, the averaged state space models of the discussed matrix-reactance frequency converters are described.