Research On Pre-Stage System Of Modular And Combined Photovoltaic Generation

The large scale grid-connected photovoltaic systems such as Photo Voltaic Power Plant and Bulding Integrated Photo Voltaic (BIPV) have been a main development trend of photovoltaic generation. The power mismatching of photovoltaic panels can be solved effectively by modular and combined photovoltaic generation system. The advantages such as high-efficiency, flexibly building and expanding, easy supervision can be acquired easily. For BIPV, the photovoltaic panels are fixed flexibly and environment difference is large. The good prospect for modular and combined photovoltaic generation system is present in BIPV.Three DC-Module-Based photovoltaic generation systems are studied, and paralleled DC-Module-Based structure is adopted through evaluating the system performancen in theory. Besides, the paralleled DC-Module-Based photovoltaic generation system is designed; Grid-connected mode and islanding mode are dicussed from the point of pre-stage system; The design demand of pre-stage paralleled dc-module is proposed.The principle of topology selection of dc-module converter is studied and applying the active-clamp interleaved Flyback-Boost converter as dc-module topology is proposed. The working theory of converter and design of circuit parameters are analysized. The simulation results prove the converter can accomplish power converting, voltage gain improving, input current sharing, the leakage energy recycling and zero voltage switching.The engineering analytical model of solar cell is built through mathematical derivation. The correctness is demonstrated through experiment and simulation methods. Based on this, the Maximum Power Point Tracking (MPPT) method of photovoltaic generation system is studied, and the two self-optimization algorithms are analysed contrastly. Consdering the contradiction of tracing precision and speed, the improved incremental conductance algorithm based on variable step is proposed, which is used as dc-module MPPT method. The simulation results prove that the new algorithm can ensure the racing precision and speed, and has a good tracing effect.The paralleled dc-module prototype is designed and produced, in which DSP TMS320F28035is adopted to realize numeric control. Power converting, MPPT, data acquisition and monitoring can be accomplished by the prototype. The experimental research of modular and combined photovoltaic generation system is carried out, which consist of dc converter’s function validating experiment, dc converter’s efficiency mensurating experiment, dc-module’s MPPT tracing experiment, paralleled DC-Module-Based system experiment and so on. The experiment’s results improve that the converter works nomally and efficiently. The dc-module can accomplish the maximum power point tracking. Besides, the paralleled DC-Module-Based photovoltaic generation system can run reliably at the mode of constant DC-bus voltage mode or variable DC-bus voltage mode.