| Global energy depletion and environmental pollution problem has become a hot issue thatpeople are concerned about, and to solve the problem people began to develop new energy whichis other than traditional energy. New energy mainly includes solar, wind, geothermal, biomassand nuclear fusion energy and so on. Solar energy as the main force of new energy is in fullspeed development, and the grid-connected photovoltaic invert as the main form of solar energyutilization will also get considerable development.At present the emphasis of grid-connected photovoltaic system are transmission efficiencyof energy and problem of grid-connected stability. In this paper, single-phase full-bridge inverteris the object of study, it has different operating mode in the different switch mode. The paperfirstly analyzes the inverter circuit operating modes in the four different switch modes, as well asthe mathematical model of the inverter. And then the hysteretic loop comparator control methodand the current control method based on SPWM are analyzed in detail. The simulation andcomparison are finished by Matlab/Simulink. Due to the switching frequency of hysteretic loopcomparator control method is unfixed, the design of the filter inductor is difficult to design, sothe current control method based on SPWM is chosen. In addition, the paper also brieflyintroduces the maximum power point tracking and the prevention of islanding effect.Signal detection mainly uses the voltage and current sampling circuit which can test thereal-time DC and AC signal. The zero-cross detection circuit can get square-wave signal whosefrequency and phase are the same as the network voltage. So we can get the network’s frequencyand phase through the zero-cross detection circuit. Signal is processed by the DSP chipTMS320F28335, it mainly includes SPWM wave, analog to digit (AD) convert, grid voltage’sfrequency and phase detection. Then the phase-locked and the feedback control are completed. |
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