Research And Implementation Of Solar PV Micro-inverter

In the increasingly tense situation of energy, the solar energy as a clean, pollution-free energy has been paid more and more attention. Solar power generation as the main form to utilize solar energy has developed a lot. PV (photovoltaic) system consists of PV array, battery, inverter and other parts. The inverter which converts the DC power into AC power is the core component. Be different from the central inverter, this article mainly focus on the micro-inverter technique.The micro-inverter system is a single-phase grid-connected system. On the basis of the analysis of several single phase system topologies, a flyback based high-frequency isolated topology is selected as the structure of main circuit. This structure is simple, low cost and small sized. This article describes the theory and working conditions of flyback converter and the inverter in detail.The control strategy of micro-inverter is discussed, firstly the equivalent model and output characteristics of PV cells is discussed and then the commonly used maximum power point tracking algorithm are compared. According to the system feature, perturb and observation method is selected as the MPPT strategy. It adjusts the duty cycle of MOSFET to change the equivalent load of PV system, which can make sure the load curve matches the output curve near the maximum power point. Inverter control uses current loop method, the current tracks with the grid voltage in phase and frequency so that the output power factor to be1. The island effect and commonly used preventive measures are both described.The hardware and software design process are introduced in detail. The hardware design includes the main circuit design, the power circuit and the sense circuit. The software design is mainly about the state machine and MPPT diagram.On the basis of the hardware platform, PV power generation experiments are completed, and the wave forms are recorded which verified that the design is correct and reachable.