Research On Protection About PV Grid-connected System

With the energy shortage and the environmental problems brought by the consumption of traditional fossil fuel energies, it is an irresistible trend to exploit new energy in recent years. Photovoltaic power generation(PV) as the main form of the development and utilization of solar energy is developed rapidly. So, it has been an hot subject research that how to design some protection circuit to deal with various faults which occuring at the PV system at present.The reliable security of PV system is the basis guarantee for either independent PV system or PV grid-connected system. However, the factors effected on PV system operation are much and complex, and they may cause the serious Electro Magnetic Interference(EMI) for nonlinear element in DC-DC convertor and invertor when the switch action quickly in short time. In addition, it also may cause over voltage or shortage voltage fault in the DC bus and over current fault in invertor when the control system operation instruction confuse or hardware circuit occur fault suddenly. So, this paper studies deeply all kinds of fault occurred possibly in PV system and developes an effective protection scheme.The thesis firstly explaines the research status about protection of PV system, and analysis overall structure and control principle of PV system, it illustrates all kinds of faults occuring at PV system from the standrad requirement for grid-connected system. Then, it studies deeply driving and protection circuit of power tube IGBT, and makes an improvement for the shortage about EXB841. Lastly, it verifies the optimization of the circuit designed accroding to PROTEUS simulation software.Then the thesis analysises detailedly the transduction pathway of EMI about PV system, and builds simulation model of commom mode current about invertor in simulation environment. It indicates that the parasitic parameter about all kinds of elements affect commom mode current about invertor differently by adopting control variate method.Finally, the thesis main does some design withhardware and hardware. It can achieves some common protection function, such as to detect the voltage in DC bus, and toachievesover current protection and overheating protection for invertor and so on. Lastly, it does some experiments about over voltage and over current protection by building experimental platform and analysises experimental results simply, that can verifies the feasibility of protection about PV system designed accroding to the experiment.