Research On Arc Fault Identification And Arc Suppression Strategy Of Photovoltaic DC Series Arc

With the increasing proportion of installed photovoltaic power generation capacity,the safety operation of photovoltaic system is increasingly concerned by scholars.The arc fault is an important factor threatening the system safety,the aging of electronic components in the PV system,the carbonization of line insulation,and the breaking of circuit breakers can produce arc,the series arc fault can not be detected and removed by the protection device in the system,and it is easy to induce fire accidents,which is the main reason of endangering the system safety.In addition,there is no zero crossing on the DC side of the photovoltaic system,it is more difficult to break off and extinguish the arc of the circuit breaker as the key equipment of the protection device than that on the AC side,the breaking performance of the circuit breaker is constantly affected by the constant erosion of the arc.Therefore,it is of great significance to study the series arc fault identification of PV system and the suppression of breaker breaking arc for system safety and reliable operation.The arc fault identification is closely related to its fault characteristics,based on the analysis of dynamic and static arc models,an improved Cassie arc model is proposed to analyze the complex series arc fault characteristics in PV system,the electrode spacing parameter is introduced in the model,the variation trend of arc voltage and current and arc state during steady-state combustion can be described by the model,the reliability of the model is verified by simulation.Based on the improved arc model,the simulation model of the PV system is built by the MATLAB/Simulink,the PV system is consisted of photovoltaic array,a Boost based circuit,and maximum power tracking,the improved Cassie arc model is connected in series with different areas of the PV DC side respectively,the complex arc failures of photovoltaic systems can be simulated,the current data in different fault areas are collected during steady arc combustion,the arc fault characteristics are analyzed from the time domain and the frequency domain,the arc fault feature vector is determined.Based on the characteristics of the vector analysis,an arc fault region identification method based on probabilistic neural network is proposed,in this method,the average current of the bus side,the average harmonic current of the bus side and the average harmonic current of the load side are taken as the characteristic input,and the different fault areas of PV system are regarded as output characteristic quantity,the harmonic mean value of characteristic quantity in frequency domain is limited to 0k Hz-50 k Hz.Based on sampled arc current data,the probabilistic neural network fault recognition model is established,BP neural network model is introduced for comparison,the results show that the recognition performance of probabilistic neural network is better than that of BP neural network,the fault area of the series arc can be identified to provide the direction for the protection device to remove the fault.Aiming at the arc problem of DC circuit breaker,based on the arc extinguishing principle of DC circuit breaker,the simulation model of DC circuit breaker is established,the influence of controllable and the uncontrollable parameters on arc burning time are discussed,the normal and short circuit breaking processes of the circuit breaker are analyzed in this paper,a hybrid DC circuit breaker arc suppression scheme based on photovoltaic charging is proposed.In this scheme,the IGBT switch is locked before the circuit breaker goes over zero and the arc is not quenched to accelerate the arc extinguishing,and the photovoltaic energy storage power supply system is designed to pre-charge the commutator capacitor and ensure the continuous operation of the circuit breaker.Based on the proposed scheme,a 150 V hybrid DC circuit breaker model is established,and the influence of IGBT switching device and RCD buffer circuit on breaker breaking is discussed.Based on the above analysis,the hybrid DC circuit breaker proposed is applied to photovoltaic DC system,the normal and short circuit breaker breaking process are analyzed by the simulation,the proposed scheme is verified.