Autonomous single-phase inverter with high quality of output voltage

The solution of the relevant problem of improving the quality of the output signal of autonomous voltage inverters is presented. In contrast to the pulse width modulation (PWM) traditionally used for this purpose, a topology containing a single-phase bridge inverter and a direct-current source switch at the input is proposed, which makes it possible to form an eight-step voltage with a total harmonic coefficient of 6.9% on the load, which meets the requirements of modern standard on the quality of electricity. The novelty of the technical solution is confirmed by the utility model patent. The optimization of the curve of the multistage signal approximating the sinusoid, using the minimum harmonic coefficient criterion, was carried out with the help of evolutionary modeling (genetic algorithm). The study of electromagnetic processes was carried out by the method of simulation. The received results confirmed the invariance of the harmonic coefficient of the inverter output voltage throughout the range of the load power factor variation 0 ≤ cos φ ≤ 1 and the stability of the system with instantaneous increase and decrease of the load. The importance of the proposed and investigated circuit solution is determined by the advantages of step modulation in comparison with the pulse-width modulation: - low dynamic losses in key elements, allowing the inverter to be used in a wide frequency range; - independence of the harmonic coefficient on the frequency and nature of the load; - reduction of mass-dimensional parameters, due to the lack of the need to install a filter at the output of the inverter, because the guaranteed quality of electricity meets the requirements of the standard; - in comparison with the method of pulse-width modulation, absence of a negative influence on the characteristics of consumers and the terms of their operation, if no higher-harmonic filters are used. The scope of the above inverter circuit includes radioelectronic equipment, communication equipment, electric drives. The greatest advantages of the proposed circuit solution are manifested when the inverter is connected to the local power supply system with renewable energy sources (solar panels, batteries), since in this case the installation of galvanically isolated rectifiers as the sources of direct current at the input of the AIN is not necessary.