Research On H Bridge Voltage Equalization Control Method Of Static Var Generator

In recent years,with the continuous access of shock,non-linear and unbalanced loads,the problem of power quality becomes increasingly prominent,and reactive power compensation device plays a very important role,especially the H bridge cascade static device is widely used.However,cascade type Static Var Generator in the dc link of all the H bridge units are independent of each other,each unit H bridge dc capacitance voltage is different,the consistency of the voltage equilibrium problems in the practical application has not been well solved,so the Static Var Generator voltage H bridge equilibrium have important research value.First of all,the thesis reviews the cascading H bridge Static Var Generator circuit topological structure,analysis based on cascaded H bridge the working principle of Static Var Generator and H bridge cascade structure,determine the various components of series-parallel loss,loss of hybrid,switch loss,and trigger delay error problems such as the cause of dc side voltage imbalance.Secondly,the hardware structure of the H bridge of the ac system is improved,and the parallel equivalent adjustable resistance at the dc voltage side of the unit H bridge is established,and the equivalent mathematical model of the adjustable resistance is established.By adjusting the internal resistance of the unit,the unit voltage is maintained basically stable,and the voltage of each H bridge is basically balanced.Then,in the aspect of software control by adopting the combination of single phase and phase voltage balancing control,hierarchical control method to achieve H bridge with single phase control is through the control switch conduction time increment of equivalent voltage vector increment,to phase in the ac side into the corresponding voltage phasor H bridge,realize single-phase voltage balance between each H bridge unit module;Phase control is to inject zero sequence voltage into each phase of H bridge group and adjust it according to the established mathematical model of zero sequence voltage calculation to achieve voltage balance on the dc side of phase and realize voltage balance of H bridge through the layered control of single phase and phase.Finally,Matlab/Simulink simulation software was used to build the simulation model of H bridge cascade structure of Static Var Generator.The simulation model was applied to the single-phase control and phase control studied,and the validity and feasibility of the Static Var Generator H bridge voltage balance control method studied in this thesis were verified by simulation.