Ivars Rankis

Dynamic behaviour of qZS-based bi-directional DC/DC converter in supercapacitor charging mode

This paper presents a bi-directional quasi-Z-source inverter (qZSI) based DC/DC converter for supercapacitor (SC) interfacing in high power applications. In the SC charging mode the proposed converter acts as a conventional VSI based step-down converter, but in the energy recovery mode it acts as a qZSI-based step-up DC/DC converter. The paper analyzes and discusses the operation of the converter in the SC charging mode. The analysis of the static model of the converter as well as the Bode diagram are presented. Theoretical results are verified by experimental results on a 500 W prototype converter.

Loss Reduction Method for the Isolated qZS-based DC/DC Converter

Abstract This paper presents an isolated quasi-Z-source inverter-based (qZSI) resonant DC/DC converter. The explanation of selection of the proposed topology is justified. Both the normal and the boost modes are discussed. Theoretical operation waveforms as well as basic expressions for the calculation of currents and voltages are proposed. A 1500 W laboratory prototype was built and experimentally verified at two operation points: that of light-load (300 W) and full-load (1500 W). All the experiments were also carried with resonant circuit and without it. The experimental results as well as performance of proposed qZSI based resonant DC/DC converter laboratory setup are presented and analyzed. Experimental and calculated characteristics showing the dependence of the load voltage and supply current on the load resistance in both modes were presented. The dynamic losses in the transistors were evaluated for the cases with the resonant circuit and without it. The main conclusions based on this study are summarized and the future tasks for development of proposed converter were defined.

Steady state analysis of the galvanically isolated DC/DC converter with a commutating LC filter

This paper presents an analysis of the continuous current and the discontinuous current mode operation of the transformer of a step-up DC/DC converter topology intended for applications with widely changing input voltages. The proposed topology consists of a LC network coupled with a single-phase inverter on the primary side and a full-bridge rectifier on the secondary side of an isolation transformer. When the input voltage is above the nominal value, the converter operates in the buck mode, but when the input voltage level is below the nominal value, the converter operates in the boost mode.

Comparative analysis of boost and quasi-Z-Source Converters as Maximum Power Point Trackers for PV panel integrated converters

This paper analyzes two maximum power point tracking (MPPT) converter topologies that are part of an interface converter for the integration of photovoltaics (PV) in the grid. Two different MPPT converter topologies (boost converter and quasi-Z-Source (qZS) converter) were selected and compared. Theoretical comparison includes an analysis of regulations for obtaining continuous source current and comparison of necessary parameters of the reactive elements of the systems. 270 W experimental prototypes of both converters were built and experimentally compared. Theoretical and experimental efficiency estimation is proposed and discussed. Also, the losses in diodes and MOSFETS are evaluated taking into account technical data from datasheets .

Analysis of heating processes of 32.3m 3 room — Heated up by central heating boiler equipped with automatic briquettes feeding system — ABFS

This paper presents analysis of heating processes of 32.3m³ room which is heated up by universal central heating boiler “Dacon - FB 36” which is equipped with experimental automatic briquettes feeding system - ABFS.

Transformer based AC pulse regulation systems

The paper is devoted to investigation of the pulse modulated systems with constant impedance load based on the application of auto-transformers in the primary circuit of pulse converters allowing to provide operation of a system with restricted range of modulated load signals and such operation conditions allow to obtain better electro-magnetic compatibility of converter with AC network without application of special filtering equipment but to respect to switches - with smaller current and voltage stresses. In the paper the main characteristics of autotransformers circuits giving possibility to provide engineering calculations are discussed in respect to the adjustability of the constant impedance load and operation parameters of the system. Some application examples are discussed - for instance for stabilizing of AC voltage of load with the changes of supply grid voltage.

Self-Excitation System for Synchronous Generator

Abstract Self-excitation for synchronous generator is described in the paper. The system is based on a buck converter input filter capacitor discharge through excitation winding of the generator. The buck converter is connected to the stator outputs through an uncontrollable diode rectifier, but excitation winding is used as a load. Input filter capacitor of the converter provides initial current pulse which magnetizes excitation system and produces the generator voltage increase, for this reason the capacitor is charged before self-excitation process starts. Results of the computer simulation and physical experiment are obtained and presented. These results show that the proposed self-excitation converter in conjunction with an input capacitor pre-charged from a low-power electronic generator actually magnetizes the generator excitation system therefore generator voltage and accordingly excitation current increases. Stabilization of generator output voltage occurs with a voltage surge, though its peak value slightly exceeds the reference one. The future investigation of the proposed self-excitation system may include definition of mathematical equations which describe transients in the generator’s self-excitation mode and development of control methods for purpose of self-excitation process control without voltage peaks. The computer model also should be improved.

The Single-Phase AC Regulator on Base of Bidirectional IGBT Switches

The Single-phase AC Regulator on Base of Bidirectional IGBT Switches In the work one of the methods for regulation of sinus shape AC voltage for middle-power loads with activeinductive character is observed. Such a regulator keeping output voltage of sinus shape must be fast-reacting and work in closed-loop system. Its shown, that for providing such features Buck and Boost pulse regulators can be applied. The only difference from DC pulse converters is that electronic switches in the system must be with bidirectional conductivity. For this reason an IGBT transistors can be applied with implemented in structure reverse diodes and if such two transistors are connected in series and with contrary conductivity then at activating both one of them will be in on-state. Realization of AC regulators with such switches is described in the work. Results of computer modeling also are given. Output voltage ripples are investigated on subject of their range and efficiency of filtering equipment on LC base. Such regulators can be applied for instance in electrical transport self supply systems.

Investigation of the Operation Speed of AC Voltage Sensor

Investigation of the Operation Speed of AC Voltage Sensor In the article the AC voltage sensor of industrial frequency-the signal former of the analogue controller with pulse-width modulation which, in its turn, controls the high-frequency electronic pulse AC voltage stabilizer, is considered.

Experimental Results from Physical Model of Bidirectional Power Flow Regulator for Power Substations of Electrical Transport

Experimental Results from Physical Model of Bidirectional Power Flow Regulator for Power Substations of Electrical Transport This article is about model of bidirectional power flow regulator for power substations of electrical transport. The paper presents an experimental model which is made in the laboratory of Power and electrical engineering of Riga Technical University. Also principal block scheme and principal schemes of that model are presented in the form of computer modeling as well as some main results of experiments are presented in the form of diagrams.