Research On Single-phase PV Grid-Connected Micro-inverter

Photovoltaic power generation has become a new way of human use energy. What’s more,solar energy grid-connected photovoltaic power generation is the trend of Photovoltaic powergeneration.As the key equipment which connect the power equipment and power grid, thereliability and safety of solar photovoltaic grid connected micro-inverter is particularly important.The traditional architecture of grid-connected photovoltaic inverter whose connection modeis connecting photovoltaic array composed of the component series parallel with powergrid-connected inverter has some problems such as module and inverter power do not match whenthere are shadows, high working temperature, limited life and monitoring capacity. So the microphotovoltaic inverter is proposed to solve the above problems. The micro photovoltaic inverterpower is in100watt PV and each photovoltaic module is equipped with a micro inverter. Thanksto its unique architecture, the micro photovoltaic inverter can ensure that each PV module is in themaximum power point and has very strong anti partial shadow ability. In addition, it has theadvantages of modular design, plug and play, easy installation and easy to extend.Firstly, this paper analyzes the advantages and disadvantages of the traditional solarphotovoltaic grid-connected inverter and micro inverter. Then it expatiate the outputcharacteristics of photovoltaic solar cells. After comparing the existing maximum power pointalgorithm, this paper selects the perturbation and observation method as the algorithm andanalyzes the causes of errors produced by the algorithm. In turn, this paper presents an optimizedMPPT algorithm based on power prediction and verifies the effectiveness of it on the simulationplatform.Secondly, this paper proposes reactive power control strategy for single-phase grid connectedinverter. By constructing two virtual volume，it can turn single phase signal to three phase signal.Using coordinate transformation, it can realize independent control of the active power andreactive power. If adopting the above two technology, it can make the grid connected microinverter inject wattless component to the power grid and regulate the wattless power outputeffectively. Simulation results show the feasibility of the control strategy.Finally, this paper designs a set of solar photovoltaic micro inverter based on FreescaleMC56F8013Carle. The inverter is a two-stage design. The front stage which adopts upper andlower interleaved flyback circuit use a separate SPWM wave controller to boost and controlMPPT. The back stage which uses the sine inverting circuit realizes the parallel function. Thecontrol strategy of grid connected micro inverter is to track the grid voltage with the same frequency and phase by inner current loop and voltage outer loop way. At last, this paper sets upthe experimental environment and conducted the experiments. It is really exciting that theexperimental results verify the feasibility of the grid connected inverter designed by this paper.