Harmonic Estimation Of Power System And Harmonic Suppression Of Inverter

With the improvement of people's production and living standards,the use of various types of non-linear electrical equipment has increased dramatically.A large number of harmonics are injected into the power grid,resulting in the increasing harmonic content in the power system,which seriously affects the power quality of the power grid.The efficiency and reliability of power system and all kinds of electrical equipment are also affected by harmonics,which make electrical equipment produce a lot of extra losses and reduce its service life,and even lead to safety accidents and even large-scale blackouts.Therefore,the research on harmonic estimation and suppression technology of power system has important theoretical significance and practical value.In order to solve the problem of harmonic pollution in power system,the harmonic detection and suppression technology in power system is deeply studied in this thesis.The main work is as follows:(1)In order to estimate the amplitude and phase of dynamic harmonics accurately,effective methods are taken to control the dynamic harmonics.In this thesis,the state estimation method of Genetic Algorithm Particle Filter(GAPF)is proposed based on the amplitude and phase of dynamic harmonics in power system.This method firstly optimizes the selection operation in the genetic operation,and adds the adaptive idea into the crossover and mutation operation,so that the crossover probability and mutation probability can adjust adaptively according to the individual fitness,thus overcoming the phenomenon of slow search speed and "premature" in the genetic algorithm.Secondly,the improved genetic operation was used to replace the resampling process in the particle filter,and the GAPF algorithm with strong parameter estimation ability was obtained,which not only solved the weight degradation and sample dilution problems caused by the increase of iteration times in the particle filter,but also retained its advantages in dealing with nonlinear and non-gaussian problems.Then,the GAPF algorithm is used to estimate the amplitude and phase of the dynamic harmonic model with noise interference.Finally,the harmonic detection results of GAPF algorithm are compared with those of particle filter algorithm,kalman filter algorithm and firefly optimized particle filter algorithm.Experimental results show that the GAPF algorithm has the advantages of higher accuracy and better real-time performance when estimating the amplitude and phase of dynamic harmonics in the non-linear and non-gaussian noise environment.(2)Cascaded multilevel inverter is an indispensable part of photovoltaic power generation.The control technology of cascaded multilevel inverters is deeply studied to reduce the harmonics injected into the power grid,so as to provide better power to the power grid.In this paper,the switching angle of cascaded multilevel inverters is taken as the research object,and the cascaded multilevel inverters are effectively controlled to reduce the harmonics injected into the power grid.In this paper,adaptive Ant Colony algorithm(Adaptive CAS)is used to solve the switching angle of cascaded multilevel inverters.Firstly,the topology and output voltage of cascaded multilevel inverters are fully analyzed,and the pulse width modulation equation of choosing harmonic elimination is established;secondly,the adaptive idea is added to the deterministic selection strategy and random selection strategy of the basic ant colony algorithm,which improves the search speed of the basic ant colony algorithm and avoids the "stagnation" phenomenon;secondly,the improved algorithm is used.The improved ant colony algorithm solves the switching angle of cascaded multilevel inverters,and controls the thyristor of the inverters by the switching angle,so as to effectively suppress the specified low-order harmonics.Finally,the harmonic suppression effect of particle swarm optimization(PSO)and genetic algorithm(GA)is compared and analyzed.The experimental results show that the switching angle obtained by the adaptive ant colony algorithm can control the cascaded multilevel inverters,which can better suppress the specified low-order harmonics.