Research And Design Of High Efficient PV Grid-connected Inverter Based On Novel H6 Bridge

In recent year,as one of the efficient way to solve the energy crisis and evvironment problem,grid-conneted photovoltaic(PV)power generation system is developing rapidly in the world and getting more and more attention.The kernel equipment of grid-conneted photovoltaic power generation system is grid-conneted inverter,and its commercial value is mostly depend on its transfer efficiency.The formation rules of common inverter topology and a novel H6 bridge topology is summarized and proposed in this paper,this novel H6 bridge can suppress the common mode current efficiently and cause smaller losses.What's more,a improved relay-bypassed topology of the front step is proposed,this topology can cause smaller losses compared with the common single-mode topology and diode-bypassed topology of dual mode.On account of the two imporved topology,a suitable modulation type and dual-mode control strategy are set out.All of these are verified on the MATLAB/Simulink platform.A 3kW model machine is also designed to verify the novel topology and control strategy in physically.The specific work is listed as follows:(1)Based on consult a great deal of literature and datum,this paper sketches the photovoltaic power generation industry development situation both at home and aboard in recent years.At same time,this paper introduces grid-conneted inverter type and its research progress,and then,the key research topics that two-stage PV grid-conneted inveter is also bringed out.(2)Focusing on analyzing the formation mechanism and suppression method of common mode voltage of the inverter stage,and calculating the common mode voltage of different topology in detail.Summarizing the formation rules of common inverter topology and proposed a novel H6 bridge topology,what's more,this paper extend the novel H6 bridge and get a cluster of H6 bridges with similar property.Modulation type and operationg principle of this H6 bridge is analyzed in detail.Lastly,the losses of the novel H6 bridge and common inverter topology is compared in quantificationally,and it confirms that the novel H6 topology is conductive to improve the transfer efficiency.(3)With regard to the fisrt boosting stage,focusing on analyzing the operationg principle of the single mode topology and dual mode topology.Aimed at the dual mode topology,a improved relay-bypassed topology is proposed,and it is verified on the MATLAB/Simulink platform.Lastly,the losses of the dual mode topology andrelay-bypassed topology is compared in quantificationally,and it confirms that the relay-bypassed topology is conductive to improve the transfer efficiency.(4)On account of the two imporved topology,a suitable modulation type and dual-mode control strategy are set out.At the first boosting stage,focusing on analyzing the property of the PV cell and making its math model,and then,the math model and maximum power point tracing(MPPT)are verified on the MATLAB/Simulink platform.At the second inveter stage,focusing on analyzing the key technology that math model of the phase-locked loop(PLL)and the auasi-resonance controller,and discretizing them in engineering.(5)A 3kW model machine is designed with the two improved topology and dual mode control strategy above-mentioned.With regard to the hardware design,the withstand voltage of the power electronic switching tube in the novel H6 bridge is analyzed in detail.The circuit design of sampling circuit of alternating signals and dc signals,driving circuit and the relationship of main controller DSP and monitoring controller is introduced.With regard to the software design,the procedure frame and file system,the task configuration in application,five work mode switching details,the functional configurations of interrupt routine which runs in background based on real-time operating system(RTOS)are introduced in detail.The two improved topology and dual mode control strategy are verified with the model machine.