Research And Design Of Single Stage Wide Input Tri-state Inverter For Photovoltaic Systerm

The traditional two stage inverter topology have two separated stage.The first stage of the inverter accomplish DC voltage boosting.The second stage inverte photovoltaic DC voltage.The topology structure is complex,much device,low efficiency.And the main problem is that there is a stored energy capacitor,the volume is big and the service life is short.The new type of photovoltaic power generation inverter with simple structure and high efficiency is great significance to the development of photovoltaic power generation.In this paper,the topology of a single stage current photovoltaic inverter is studied.Its operation principle and modulation strategy are analyzed.The specific research contents are as follows:the mode of operation is analysed,the state space average model is obtained.On the basis of the above analysis,the SPWM(Sinusoidal Pulse Width Modulation)method is proposed,which is suitable for this topology.It establishs matlab/simulation platform and the simulation results show that the inverter topology and modulation method can achieve the boost-buck voltage and inverter.It can complete the power decoupling between input and output.Considering the limitation of the range of the DC side input voltage of the inverter,H shape inductance is proposed to replace a single inductance.A single stage wide input photovoltaic tri-state power generation inverter is proposed.The operating principle of the inverter is analyzed,the steady-state and dynamic model is established,and the dynamic response characteristics are analyzed.PI control of output voltage and power is completed.The simulation model was built and simulate.The result show that single stage wide input photovoltaic inverter have good dynamic response,it can complete decoupling between the input power and output power.It5s the better topology to photovoltaic power generation system.Then photovoltaic model and the maximum power point tracking algorithm are studied,and the system selected the improved variable step size MPPT algorithm to complete the maximum power point tracking.Finally,the hardware and software of photovoltaic power generation system is designed.The photovoltaic power generation system prototype is completed.Experimental verification of photovoltaic system,including:the basic function of the inverter experiment,MPPT experiment,different load experiment,PI control experiment and system efficiency test.Experiments show that the photovoltaic power generation system is working properly,good output characteristic,variable step size MPPT algorithm can quickly and accurately track the maximum power point,the control strategy can make the output voltage and the MPPT coordination,efficiency of the system can meet the requirements of photovoltaic power generation system.