Performance of a Voltage Step-Up/Step-Down Transformerless DC/DC Converter: Analytical Model
The authors present an analytical model for a voltage step-up/step-down DC/DC converter without transformers. The proposed topology is a combination of classic buck and boost converters in one single circuit but with differing operational principles. The converter is developed for a wind power autonomous supply system equipped with a hydrogen electrolytic tank and a fuel cell for energy stabilization. The main power source of the hydrogen-based autonomous supply system is energized by a synchronous generator operating on permanent magnets and equipped with a diode bridge. The input voltage of the converter in this case varies in the range 0-700 V, while its output DC voltage must be 540 V according to the demand of other parts of the system. To maintain the rated voltage, a special electrical load regulation is introduced. The calculations of the converter, the generator (equipped with a diode bridge) as element of the power system supply joint, and the load replaced by resistance are verified with PSIM software.
The paper presents results of analysis of a possible solution for enhancement of frequency converter (FC) AC supply power parameters. The method proposed is based on switched stabilisation of DC current of FC front-end rectifier unit. Such stabilisation allows obtaining rather good AC supply power parameters, i.e., its power factor and total harmonics distortion (THD) indicator for phase current. The paper also demonstrates a possible realisation scheme, a simplified mathematical description of processes in the scheme, as well as methods for consideration of its parameters, accounting the rated power of FC and the appointed level of the rectifier DC current continuity ratio. The results of computer simulation, to a great extent, testify a possible enhancement level.
Investigation of the Input Unit of Frequency Converter
The paper considers scheme of single-phase input unit with AC circuit reactor of frequency converter, its operation, dependencies of characteristics on parameters of the scheme and influence on supply network.
According to the strategical objectives of the use of the renewable energy sources, it is important to minimise energy consumption of conventional power grid by effective use of the renewable energy sources and provi-ding stable operation of the consumers. The main aim of research is to develop technical solutions that can provide effective operation of the wind generators in the small power DC microgrids, which also means wind energy conversion at as wider generator speed range as possible.