Research on a novel detection method for fundamental positive sequence active current

The rapid and accurate fundamental positive sequence active current detection method is very important for the power quality control. However, many traditional methods need to use the phase locked loop (PLL), the low pass filter (LPF) or αβ and dq coordinate transforms which increase the complexity of the detection and have the large detection errors in three-phase unsymmetrical system. In view of these problems, this paper proposed a novel detection method. Firstly, this method, with the theory of the fan-in vector transformation, transfers a three-phase system into a single-phase system which simplifies the detection method. In addition, it designs the extractors for fundamental positive sequence current and voltage with the analyzing of the selective frequency characteristic of an amplitude integration signal. Finally, through the simple calculation, the fundamental positive sequence active current was detected. This detection method needs neither a PLL nor a LPF, and can omit some complex calculations for using αβ and dq coordinate transforms. It not only greatly reduces the calculation quantities and makes a better real-time detection but also achieves the accurate result in three-phase unsymmetrical system. Results of the simulation MATLAB/Simulink verify the validity and feasibility of the proposed method.