针对采用虚拟磁链算法的无电网电压传感器存在的直流偏移等问题,提出基于一阶低通滤波器和高通滤波器串联结构的改进磁链观测器,利用改进的磁链观测器得出虚拟磁链,提高了观测的精度。在得到虚拟磁链的基础上,针对不同电网频率运行条件,利用锁相环思想提出电网角频率的计算结构,并由虚拟出的磁链与电压的关系来重构电网电压。此外,将所提无电网电压传感器策略应用于网侧变流器系统中,在两相静止坐标系下设计虚拟同步控制结构,相比于旋转坐标系,可省去控制内环的解耦环节,同时还能简化坐标变换环节,避免了因坐标变换中角度不准而引入的不稳定因素。最后,通过仿真与实验验证所提控制策略与磁链观测器的有效性与可靠性。
Abstract
This paper proposes an improved flux observer based on a series structure of a first order low-pass filter and a high pass filter to solve the DC offset problem of grid voltage sensorless strategy using the virtual flux algorithm, by utilizing this improved flux observer to derive the virtual flux, the precision of observation is enhanced. Based on the virtual flux obtained, a calculation structure of grid angular frequency is proposed using the idea of phase locked loop for different grid frequency operating conditions, and the grid voltage is reconstructed from the relationship between the virtual flux and voltage. In addition, the proposed grid voltage sensorless strategy is applied to the grid side converter system, and a virtual synchronous control structure is designed in a two-phase static coordinate system. Compared to a rotating coordinate system, the decoupling process of the control inner loop can be omitted, while the coordinate transformation process can be simplified, avoiding the instability factors caused by inaccurate angles in coordinate transformation. Finally, simulation and experiments verify the effectiveness and reliability of the proposed control strategy and flux observer.
关键词
变流器 /
磁链 /
无传感器控制 /
虚拟同步控制 /
静止坐标系
Key words
power converters /
flux linkage /
sensorless control /
virtual synchronous control /
static coordinate system
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