Research On Single-Phase Grid-connected Photovoltaic Inverter Based On Dual-Core Controller

Photovoltaic(PV) generation has a bright prospect due to the enormous reserves and pollution-free. Grid-connected PV inverter is an important part of PV generation system. Moderate and small power single-phase grid-connected PV inverter is lowly-investment, more flexible and adaptable which can be used in the household, the company and other occasions. It's an effective way to promote the PV generation. Controller plays a important role in determining the inverter's performance and cost.The significant technologies of grid-connected PV inverter include the grid synchronized phase lock, maximum power point tracking and islanding detection. In this paper, the principle of these technologys were analysised, and some conventional approachs were introduced. Combined with the characteristics of moderate and small power PV inverter, the design solution was given. After analyzing the reason for perturb and observe(P&Q) method's misjudgment under rapidly changing environmental or shaded conditions, this paper proposed an optimized P&Q method based on power prediction and shadow judging algorithms.On the basis of two stages grid-connected PV inverter's topology, the control strategys were analyzed in this paper. A high gain boost circuit using two inductors as the system's DC-DC converter was designed. It can improve the inverter's DC input range availably. The grid-connected control strategy was presented and simulated, including the methods of inner cureent loop, external voltage loop modeling, and PI regulator design. Some optimized algorithms such as grid voltage feed-forward control, current prediction and DC off-set suppression were presented.The chip IRMCF143 was used as the system's controller, which integrated two processors specially for inverter control. This controller's internal blocks and mechanism were introduced as follows. The design scheme for 800W single-phase grid-connected PV inverter was presented at last. Through the design of the MCE processor and 8051 processor independently but organically, the system achieved the optimization of performance, cost, and time.Lastly, the prototype was implemented and the grid-connected PV inverter experiment platform has been built. As a result, the grid-connected operation was realized. The waveforms and data were recorded and analyzed, and experimental results showed that the current THD and efficiency reached less than 4% and more than 93% respectively. The system achieved the functions of the design scheme.