基于DFT的无锁相环三相有功电流实时检测方法

摘要

在基于瞬时无功功率和傅里叶变换等的单相、三相电路谐波检测方法中,检测性能受锁相环的输出信号误差制约,而不带锁相环的检测方法难以分离基波有功、无功电流.考虑电网电压不对称且畸变的情况,文中提出一种基于迭代DFT变换的无锁相环三相有功电流、无功电流检测方法.利用αβ变换将三相变为两相,并将α轴和β轴分量构成复数,经迭代DFT变换后仅输出正序分量.再根据电压电流的相位特征求出功率因数,即可得到基波有功、无功电流.该算法具有计算量小、响应延时短且固定、不受电压畸变影响的特性.理论分析和仿真证实了所提出方法的正确性.%The effectiveness of single -phase and three -phase detection method based on instantaneous reactive power theory and Fourier transformer is limited by phase lock loop's (PLL) signal error. The detecting methods without PLL are difficult to detect active and reactive current of fundamental frequency. A PLL-less three-phase detecting method is presented to detect active, reactive and harmonics currents using iteration DFT. This kind of detecting method has strong immunity to voltage distortion, αβ transformer is used to transform three-phase into two-phase, and α-axis and β-axis components are combined into a complex. Positive sequence component can be obtained by iteration DFT. And the power factor can be obtained according to the phase difference of voltage and current. Active and reactive currents can be detected by above process. Theory analysis and results of simulation prove the validity of this method.