Open Circuit Fault Diagnosis Of Photovoltaic And Wind Power Converters Based On Current Characteristics

With the rapid development of modern society and the gradual shortage of global fossil energy,the development of renewable energy has become the only way to solve the problem of modern energy.Solar and wind power are two of the most promising types of renewable energy.Modern society is increasingly dependent on these two kinds of energy,and the reliability and stability of photovoltaic and wind power generation systems are becoming more and more important.Converters,which are mainly composed of power electronic devices,are an essential part of photovoltaic and wind power generation systems.Studies have shown that the switching tube device is the component with the highest failure rate in the converter.In order to ensure the stable operation of photovoltaic and wind power generation system,it is necessary to be able to quickly diagnose the fault of converter switch tube.In this thesis,the converters of photovoltaic and wind power generation systems are taken as the research object.Firstly,the simulation and modeling of these two power generation systems are carried out,and then the open-circuit fault diagnosis method of converter switches in photovoltaic and wind power generation systems is proposed.The research content of this thesis is mainly divided into two parts: First,analyzed the offgrid photovoltaic power generation system of three-phase voltage type bridge type inverter under different switch tube open-circuit fault of output current waveform,found that the output current is half cycle or failure to meet in the negative half cycle change to keep the phenomenon of zero,based on the current feature,designed a kind of based on the average output current in a cycle of fault diagnosis methods,According to the relationship between the calculated diagnostic variables and the adaptive threshold,the open circuit fault diagnosis of single and double switch is carried out.Secondly,the current waveforms of the rotor side converter in the direct-driven permanent magnet wind power generation system under different open circuit faults of the switch tube are analyzed.It is found that the current in the fault phase will continue to cross zero,and the non-fault phase current will also change specifically.Based on these two current characteristics,feature extraction is applied to single and double tube open circuit fault diagnosis.Then,according to the difference of the current continuous zero crossing position,a new open circuit fault diagnosis method for single-double switch is designed,which only needs to analyze the local current,and the calculation amount of the diagnosis method is reduced.Finally,simulation experiments are carried out to verify the diagnostic variables and adaptive thresholds of each phase of the three-phase voltage bridge inverter in the photovoltaic power generation system.According to the relationship between the two,the open-circuit fault diagnosis of the switch tube of the three-phase voltage bridge inverter can be accurately carried out.The final diagnostic signal can be obtained by calculating the current zero crossing sign and open circuit fault signal of each phase of the converter in the direct-drive permanent magnet wind power generation system.The diagnostic signal can quickly and accurately reflect the switch tube that has the open circuit fault.For the improved fault diagnosis method,the fault phase is judged according to whether the current continues to cross zero,the average value of the current before and after the zero crossing is calculated,and the fault phase switch tube is located according to the change of the average value.The experimental results show that the improved method can effectively diagnose single and double tube open circuit faults.In addition,a fault diagnosis experiment under wind speed disturbance is carried out,and the experimental results show that the proposed method is robust to wind speed disturbance.