Selective harmonic compensation by smart inverters using multiple-complex-coefficient-filter (MCCF) during unbalanced fault condition

An improved methodology for selective harmonic detection and compensation (SHC) is proposed for smart inverters used as a Shunt Active Power Filter (SAPF). It is equally applicable in abnormal operating conditions such as in the event of an asymmetrical grid fault. A Multiple-Complex-Coefficient-Filter (MCCF) based Phase Locked Loop (PLL) is designed and tested for 5th and 7th harmonic compensation. Associated harmonic as well as fundamental current controllers in Synchronous Reference Frame (SRF) are designed and verified through simulation. Multiple linear rotating Proportional-Integral (PI) controllers are deployed for regulating the line current. MATLAB-SimPowerSystems package is used as a software platform for the demonstration of controllers' transient and steady-state performance. The proposed approach can selectively detect and effectively reduce harmonics to meet IEEE standards. This approach can also be extended to n number of harmonic compensation in a fast and accurate manner.