Abstract
In this project, a grid-connected boost-half-bridge photovoltaic (PV) microinverter system and its control techniques are presented. In order to achieve low cost, easy control, high efficiency, and high reliability, a boost-half-bridge dc-dc converter using minimal devices is introduced to interface the low-voltage PV module. A full-bridge pulse width-modulated inverter is cascaded and injects synchronized sinusoidal current to the grid. An ANFIS (Adaptive Neuro Fuzzy Interference System) current controller is proposed and it is used to regulate the grid current. High power factor and very low total harmonic distortions are guaranteed under both heavy load and light load conditions. Dynamic stiffness is achieved when load or solar irradiance is changing rapidly. In addition, the dynamic behaviour of the boost-half-bridge dc-dc converter is analysed; a customized maximum power point tracking (MPPT) method, which generates a ramp-changed PV voltage reference, is developed accordingly. Variable step size is adopted such that fast tracking speed and high MPPT efficiency are both obtained. A 210W prototype was fabricated and tested. Simulation and experimental results are provided to verify the validity and performance of the circuit operations, current control, and MPPT algorithm.