A DC TO AC CONVERTER WITH A HIGH FREQUENCY LEVEL

Abstract

Two block diagrams of DC-AC converters with a voltage curve of a given frequency close to the sinusoidal shape without a high-frequency section and with a high-frequency section are considered. In the converter circuit without a high-frequency link, an autonomous voltage inverter (AVI) is used, and in the converter circuit with a high-frequency link, a high-frequency AVI (AVI HF) and a direct frequency converter with quasi-single-band modulation (DFC QF) are used. In both of these converter circuits, for electromagnetic isolation between the DC voltage source and the load, a power transformer is envisaged, to match the input and output voltages. To improve, ensure and obtain on the load the output voltage curve close to the sinusoidal shape, filters are used, which is the simplest way of improvement without a selective elimination of distorting harmonics of non-sinusoidal periodic voltage with multiple switching of valves, without pulse-width modulation, and so on with the complication of voltage inverter and DFC control systems. At the same time, in the first converter circuit, one filter is used: connected between the output of the inverter and the input of the output transformer, and in the second converter circuit, two filters are used, one of which is connected between the output of the AVI HF and the high-frequency transformer, and the other - between the output of the DFC with the QF load. Since the output voltages of AVI and DFC are non-sinusoidal periodic functions, using the methods of harmonic analysis and switching functions, mathematical descriptions of the output voltages of AVI and DFC are obtained in the form of a trigonometric Fourier series. A numerical assessment of the weight and size parameters of transformers and filters in relative units is carried out. It is shown that the use of a converter with a high-frequency link based on AVI HF and DFC with QF allows to significantly reduce the mass and dimensions of power electromagnetic elements.