基于三维空间矢量的三角形联结级联SVG直流侧电压控制方法研究

三角形联结级联H桥拓扑静止无功发生器(SVG)能够动态补偿无功负序功率,提高功率因数,抑制电压闪变和波动,改善电网电能质量,近年来得到了广泛研究。对于级联H桥结构的静止无功发生器,其直流侧电压控制问题一直是研究的热点问题。空间矢量调制相对于载波调制,便于微机实时控制,具有电压利用率高和开关损耗小等特点。基于空间矢量调制的直流侧电压控制的方法在三角形联结级联H桥还没有应用。提出了基于三维空间矢量的直流侧电压三层控制结构:第一层为总的直流侧电压控制;第二层为相间均压控制,将每一相视为一个H桥,三相之间采用三维空间矢量法,在开关周期内通过能量函数选择合适的零序分量注入调制波中产生零序电流,实现三相之间的实时均衡控制;第三层为模块间均压控制,实现每相内部各H桥模块直流侧电压等于给定值。基于三维空间矢量的零序电流选择方法能够在单位开关周期内产生零序分量,从而产生任意次零序电流实现对直流侧电压控制,具有较快的动态响应速度,仿真和实验结果验证了该方法的正确性和有效性。

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.