A. Dmowski

A novel series-resonant DC/DC converter with full control of output voltage at no-load condition-computer simulation based design aspects

A novel series-resonant converter (SRC) with added boost stage assuring full control over output voltage is presented. To make easy the design of a SRC, a computer program was prepared which builds a database consisting of different operating points of the SRC with varying LC values, providing a convenient tool for analyzing converter work and allowing selection of LC elements for a needed application. A half-bridge configuration works with switching frequency from 50 kHz up to 100 kHz, giving an output power of 1.5 kW. A full-bridge topology works in the same frequency range and gives output power of 4 kW. Both converters work on the rectified 380 VAC mains and the output voltage is max. 60 VDC. The boost stages were designed to allow output voltage regulation from 20 V to 60 V.<<ETX>>

Operation of photovoltaic power systems with energy storage

Photovoltaic (PV) power systems are described in the article. Power generated from renewable energy sources is not stable because of the energy fluctuations caused mainly by atmospheric conditions. Therefore, in order to improve the parameters and stability of the power system, PV power plants should cooperate with electrical energy storage system such as electrochemical batteries. Moreover, because of the reason that PV power plants are often located on the terrain which is accessible by the man, galvanic isolation may be obligatory. Since the efficiency of the power conversion in PV power systems has to be maximized, soft switched resonant power converters, in which switching losses are minimized, are utilized in such PV power systems. Moreover, grid-connected PV inverter which is a crucial element of the PV power system is presented in the article.

The control strategy for a Solid Oxide Fuel Cell Hybrid System

Based on mathematical modeling and numerical simulations, the control strategy for a Solid Oxide Fuel Cell Hybrid System (SOFC-HS) is presented. Adequate maps of performances with three independent parameters are shown. The independent parameters are as follows: stack current, fuel mass flow and turbine-compressor shaft speed. Those parameters can be controlled by external load, fuel valve and turbine-compressor shaft speed, respectively. The control system is purposed to meet many constraints: e.g. stack temperature, steam-to-carbon ratio, compressor surge limitation etc. The aim is to achieve maximum efficiency of power generated within those constraints. Governing equations of SOFC-HS modeling are given. An adequate simulator for the SOFC module was produced and described. Based on this simulator, the control strategy was obtained. The performance of this SOFC-HS is shown in various working environments.

The Control Strategy for a Solid Oxide Fuel Cell Hybrid System

Based on mathematical modeling and numerical simulations, the control strategy for a Solid Oxide Fuel Cell Hybrid System (SOFC-HS) is presented. Adequate maps of performances with three independent parameters are shown. The independent parameters are as follows: stack current, fuel mass flow and turbine-compressor shaft speed. Those parameters can be controlled by external load, fuel valve and turbine-compressor shaft speed, respectively. The control system is purposed to meet many constraints: e.g. stack temperature, steam-to-carbon ratio, compressor surge limitation etc. The aim is to achieve maximum efficiency of power generated within those constraints. Governing equations of SOFC-HS modeling are given. An adequate simulator for the SOFC module was produced and described. Based on this simulator, the control strategy was obtained. The performance of this SOFC-HS is shown in various working environments.

Electronics And Power Electronics Devices In Dissipated Power Systems With Fuel Cells

The fuel cell features are presented in the paper. During description of systems of supplying auxiliaries with fuel cells, special attention is paid to problems of electronics and power electronics. The article has presented range of schemes, with fuel link matches cooperating. Cooperation of fuel link from different kinds of electronics and power electronics will enable realization of the following electronic purposes: operation with stabilized constant DC output voltage, operation with stabilized constant AC output voltage and operation fuel cell a sources connected with inverter in distributed AC system. Accuracy of the choice of suitable solutions of power electronics systems will be confirmed by the chosen results of simulation and laboratory investigations.

High efficiency resonant converter based on MCT

The trend to reduce the weight and size of power converters resulted in an increase of switching frequency. The standard power device for medium and high power applications is the IGBT. Due to techniques to decrease switching losses, the space and weight limitation of modern converters are conduction losses. When switching losses are reduced, a further increase of efficiency with all its advantages is possible by the use of new power devices like MCTs (MOS controlled thyristors). The bad hardswitching behavior of the MCT practically eliminates the possibility of using it in a conventional high-frequency converter. All of the advantages of the MCT can be used in zero-current switching topologies (zero turn-on and off, ZCS). The paper presents an off-line (520 V DC-15 kW) resonant converter based on MCTs, operating at 100 kHz. A novel, advanced series-resonant converter topology with ZCS is also presented. It utilizes the advantages of low conduction losses of the MCT, promises eliminating turn-off losses and highly reducing turn-on losses. The full load efficiency of the converter is better than 98%. Design, simulation and practical results are discussed.<<ETX>>