Research On Dynamic Voltage Restorer Based On Three Single-phase H Bridge

Currently power quality sensitive electrical equipment large number of applications resulting in users advance more strict requirements in a variety of power quality parameters , While many loads especially power electronic devices, produce more and more interference to the stable operation of power grid, custom power is proposed for this contradiction. Dynamic Voltage Regulator (DVR) is one of those that has the advantages of fast dynamic response, high efficiency, low energy storage requirements, DVRhas becomes one of the most effective and the most economical means to retort voltage drop.Firstly,This paper summarizes the importance of power quality for custom and the main reasons that affect power quality and the principal means of improving power quality, also propose the topology of the dynamic voltage restorer applied in low and medium voltage level side and analysis of the different compensation strategies.Secondly, This paper detailed analysises the single-phase inverter in DVR, a single-phase inverter model is established, different modulation strategies are analyzed, the LC filter is designed. Followed Analysis of the shortcomings of the open-loop control, dual-loop control system with current feedforward is proposed. And the compound control system of dual-loop control system combined with the voltage command feedforward eliminate the phase difference between command voltage and output voltage and improve the dynamic response,That the coupling transformer has little effect on the inverter is concluded through analysis.Then put forward the theory of thyristor forced turn-off and used strategy on forced turn-off,analyze a variety of the wrong extreme situation near zero where maybe appear thyristor turn-off error,Analysises show that the strategy will not cause the error of turn-off thyristor, if reasonable strategy is adopt.Finally, the inverter carry out experience of sudden addition load and sudden reduction load throuhg chaging load,and execute instruction sudden addition and sudden reduction and force turn-off thyristor through the PC issue various instructions to DSP. The simulation and experimental verify the theoretical analysis,show that the the inverter can output stability voltage and turn-off thyristor will not be mistaken.