Research On Micro-grid SAPF Based On Cascade H-Bridge

With the development of society,bringing the environment pollution and the shortage of energy and other issues seriously affect people's lives.The micro-grids connect the various distributed energy well together.Better to achieve the application of new energy and improve energy efficiency.However,there are a large number of rectifier inverter devices and non-linear loads in the micro-grid,which seriously affect the power quality of the micro-grid.Active power filter has the ability to compensate for harmonics and reactive current,and it has been widely used in the power quality management.With the upgrading of the grid voltage level,APF is not suitable for high voltage and high power working environment,and the switching frequency of electronic devices decreases with the increase of capacity.The lower switching frequency affects APF compensation performance.In this paper,the cascade H bridge SAPF topology is adopted.And the multi-level structure is analyzed and studied.A number of common harmonic detection methods are discussed,and the method based on instantaneous reactive power detection is introduced.An adaptive prediction algorithm based on improved momentum is proposed to detect the harmonics.Improve the accuracy of the detection of harmonics.The momentum term improves the fastness and steady state error of the detection algorithm.When the system load changes abruptly,it causes the current to fluctuate.At this time,the momentum term has a great influence on the update speed of the detection algorithm.When the steady state is reached,the momentum term converges to a minimum value,The impact is minimized.This not only improves the convergence speed of the algorithm,but also ensures the steady-state error of the algorithm,and the algorithm can track the system mutation well.The cascaded SAPF is controlled by the unipolar frequency doubling phase shift carrier modulation method.The influence of different modulation ratio cascaded SAPF output voltage and the distribution of the inherent output harmonics of the device are analyzed.The DC voltage of the device is controlled by stratification.The upper layer controls the total voltage of each phase,and the lower layer controls the DC side capacitor voltage of each H bridge.Simulink is used to build the simulation model of micro-grid and cascade H bridge SAPF,and simulation analysis is carried out.Set up the experimental platform prototype test analysis.