Comparison of Performance of Harmonic Filters Using PQ Theory

Harmonic currents produced by nonlinear loads, such as Variable Frequency Drives (VFDs), lead to voltage distortion due to voltage losses in the electrical distribution network. This voltage distortion effect, which correlates with the system impedance, negatively impacts the system's overall performance. It is crucial to assess the harmonic characteristics of the connected load to predict distorted voltage levels at the Point of Common Coupling (PCC). The grid system's harmonics are examined by simulating the grid in MATLAB, followed by FFT analysis to identify the harmonics present within the system. The shunt active power filter (SAPF) is a widely recognized solution for harmonic mitigation. However, while the SAPF lowers grid impedance, it can also lead to higher harmonic current distortion. To reduce total harmonic distortion, a hybrid filter comprising a series active power filter and a passive filter, grounded in the generalized theory of instantaneous power in three-phase circuits—commonly referred to as P-Q theory—is implemented in the system.