Research On Topology Of Single-phase Non-isolated Photovoltaic Grid-connected Inverter And Anti-islanding Strategy

Since the Industrial Revolution,the unplanned and uncontrolled exploitation and utilization of traditional energy by human activities has caused serious environmental problems.The scientific and effective solution is to look for and to develop clean energy,reduce the environmental pollution caused by fossil energy,ensure the sustainable development of society.Therefore,green photovoltaic power generation has become a research hotspot.Firstly,the research background and current status of photovoltaic power generation technology and related grid-connected standards are introduced,the causes and harms of common-mode current in photovoltaic grid-connected inverter systems are described,and the main circuit topology,working process and the resulting common-mode voltage and common-mode current of the common single-phase photovoltaic grid-connected inverters are analyzed in details.The analysis indicates that the existing single-phase non-isolated photovoltaic grid-connected inverter topology,which can suppress common-mode current,cann't meet the requirements of loss,efficiency,and cost at the same time.Then introduce the causes and hazards of islanding effect and commonly used island detection methods.In view of the above analysis,this paper proposes a novel single-phase non-isolated photovoltaic grid-connected inverter topology with high efficiency,low loss and low cost that can suppress common-mode current in a distributed MPPT photovoltaic system.A detailed analysis of the circuit structure,operating principle,common-mode voltage and common-mode current and performance advantages was given.Then the paper discusses the control structure and principle of the single-phase photovoltaic grid-connected inverter system and the applicable island detection method,as well as introduces the design of system hardware circuit and software program.Finally,single-phase photovoltaic grid-connected inverter system,common-mode voltage and common-mode current based on this topology and single-phase photovoltaic grid-connected inverter system using AFD method are verified by simulation using Matlab/Simulink,and a hardware experimental platform are also established to experimentally study the SPWM drive waveform,current loop and grid outputcharacteristics.Simulation and experimental results demonstrate the feasibility of a novel single-phase non-isolated photovoltaic grid-connected inverter topology that can suppress common-mode current and the correctness of theoretical analysis.