Research of DC voltage control based on space vector modulation method in the delta connection cascaded SVG

Static var generator (SVG) of delta cascaded H-bridge structure can dynamically track the change of reactive load,improve power factor,restrain the voltage sag and fluctuation,and improve power quality of the grid,so it is widely researched in recent year.The DC link voltage control is a hot issue to cascaded H-bridge SVG of delta connection structure.Compared with the carrier modulation method,Space vector modulation method is suitable for a real-time implementation in digital signal processors with wide linear modulation range and lower switching loss.But the DC voltage control method based on space vector modulation in delta connection cascaded SVG has not yet been applied for DC-side voltage control.Therefore,this paper proposes three layers control system,the first layer is total DC-side voltage active power control; the second layer is interlayer voltage balance control and each phase treats as a H-bridge and use 3D SVPWM method between each phrase; the third layer applies voltage balance control among each module in each phase to achieve equivalent result between the given value and the DC-side voltage of each H-bridge.The zero-sequence current based on 3D-space vector modulation can generate in each unit switching cycle,so it can produce arbitrary order zero sequence current to achieve the DC voltage control with high speed of dynamic corresponding.Lastly,the simulation and experiments results verify the correctness and validity of the method.