Research Of Grid Connected Photovoltaic Inverter Based On Direct Power Control

The neutral point clamped three level inverter is widely used in renewable energy power generation because of its advantages of higher power quality and less harmonic output waveform.In this paper,the mathematical model of neutral point clamped three level inverter,SVPWM modulation technology and islanding effect of grid-connected generation are studied based on neutral point clamped three level inverter,based on these research,improve the performance of photovoltaic inverter system.This paper summarizes the background and significance of the research,analyzes the structure of photovoltaic grid-connected power.This paper focuses on the research background and significance of three-level inverter,expounds the topology structure of three-level inverter,and analyzes the industry standard of current photovoltaic power generation.The key technology of grid-connected photovoltaic power generation is studied,including modulation technology of three-phase power network,maximum power point tracking technology of photovoltaic power generation,control method of grid-connected photovoltaic generation inverter,islanding effect of photovoltaic power generation,filter technology of photovoltaic generation and the corresponding filtering effect.This paper focuses on the research of neutral point clamped three level inverter,mainly analyzes the topology of neutral point clamped three level inverter,and focuses on the working principle of the inverter and switching between switching operation.This paper focuses on the mathematical model of neutral point clamped three level inverter,including the mathematical model of active inverter and passive inverter,and discusses the equivalent circuit diagram under different coordinate system;Finally,the advantages and disadvantages of this inverter are introduced.The modulation method of neutral point clamped three level inverter is studied.First,the SPWM and SVPWM modulations of three-level inverter are studied,then,a simplified reference vector of the traditional SVPWM modulation method is proposed.Based on the Matlab / Simulink simulation platform,the simulation results show that the effectiveness of SVPWM algorithm can not only get good waveform,but also simplify the computational complexity.According to the islanding problem,active frequency drift and power disturbance anti-islanding strategy are the main research methods,aiming at the effect of traditional active frequency drift scheme in islanding detection is not obvious,a method of changing injection disturbance waveform is proposed.The simulation results in Matlab / Simulink simulation environment show that the efficiency of the active frequency drift strategy,not only makes the time of islanding detection meet the national requirements,but the total harmonic distortion value is smaller.