Research On Harmonic And Reactive Power Compensation Based On Tuning Filter And D-STATCOM

The rapid development and widespread use of new-style electrical equipments in distribution networks brings unavoidable power quality problems to the power system,mainly including harmonic pollution,low power factor,three-phase voltage imbalance,voltage fluctuation,which directly affect the safety,stability and economic operation of the electric equipments in the power system.The harmonic control in power grids is dominated by the installation filter,the passive filter(PF)compared to the active filter is still the main device for harmonic control.D-STATCOM can not only improve the power factor of the power grid,but also can solve the three-phase unbalanced power quality problem,which is mainly because the compensation of reactive power and unbalance are its basic functions.Aiming at the problems of harmonic pollution,low power factor and three phase unbalance in distribution network,the compensation scheme that the passive filter and the static synchronous compensator operate together can be used to improve the power quality of the power system.Firstly,according to the working principle of the traditional passive filter,the reason of the detuning due to the influence of parameter changes is analyzed,and a transformer-type tunable passive filter based on thyristor control is proposed.The equivalent circuit model is used to detailedly derive the mathematical relationship between the trigger angle of hyristor and the parameters L and C of tuning filter.The simulation model of the tunable passive filter is constructed and its filtering and tuning performance is simulated.It is proved that the tunability of this based on thyristor-controlled transformer-type passive filter is effective.Secondly,D-STATCOM is chosen to compensate reactive power and imbalance in power system.At the same time,the topology and advantages of D-STATCOM are introduced in the dissertation.However,the accurate detection of the compensation current command information required by the power grid is the key to the efficient operation of D-STATCOM.When the grid voltage is distorted or unbalanced,the traditional i_p-i_q instruction current detection method will have detection errors because it can not accurately detect the positive sequence component of voltage fundamental wave,which can have a effect on the accuracy of the compensation command current detection and can make the compensation greatly discount.Therefore,an improved i_p-i_q compensation instruction current detection method is proposed.This method can eliminate the detection errors of the power grid under non-ideal conditions and thus can accurately detect the compensation command current,which is verified by simulation.Finally,the theoretical analysis shows the characteristics and advantages of the parallel operation of the passive filter and D-STATCOM.Based on the previous simulation model by increasing the harmonic load,the filtering effect of D-STATCOM running alone is not ideal.In this case,the measure is to add a passive filter on the load side.The theoretical analysis and simulation experiments are combined to verify the correctness and feasibility of the compensation for parallel operation of passive filter and D-STATCOM.