Research On Single - Board Photovoltaic Grid - Connected Inverter

With the continuous decrease of PV panel’s production costs, household small PV systems are introduced into more and more people’s homes. The demand for relevant micro-inverters is increasing as well. The efficiency and appropriate topologies are hotspots of relevant researches. In this paper, a grid-connected inverter is designed for a single solar panel. The main contents of this paper are as follows:(1) The status of current researches on the micro inverter was introduced. Two-stage structure was chosen for this inverter.(2) Former stage of the inverter was designed. Through the comparison of various topologies, a new half bridge current fed LLC converter which is suitable to occasions with low input voltage and high input current was chosen as the former stage’s circuit. According to the comparison analysis with traditional LLC converter, the working principle and models of this new converter was proposed. The stability was analyzed through simulation by Saber and relevant compensation design was given. Several common maximum power point tracking algorithm was compared and analyzed. Variable step disturbance observation algorithm was chosen to be the MPPT algorithm of this paper.(3) Latter stage of the inverter was designed. The full-bridge inverter with sinusoidal pulse width modulation was chosen as the latter stage’s circuit to invert direct-current to sinusoidal waves. LCL filter was designed. The double loop control method with capacitive current inner loop and grid connected current outer loop was used to suppress the resonance peak of LCL filter and track the grid connect current. The phase-locking algorithm was used to connect the inverter to the grid.(4) The simulation and experiment was given. The simulation was achieved by Saber and Matlab. The inverter was realized by the control algorithms based on Microchip’s ds PIC30F2020. The experimental results and analysis was given and analyzed.