A Parallel Compensation Technique to Improve the Convergence of Iterative Harmonic Analysis

—This paper was presented at the conference “ICHPS VI” (Bologna - Italy, 1994), but it is not available to the scientific community because the conference proceedings were never published. The recent interest in Iterative Harmonic Analysis (IHA) approaches has suggested proposing again the content of the missing paper, given its ability to overcome the convergence difficulties, which historically have limited the utilization of IHA. The paper focuses on the convergence difficulties of the iterative approaches based on sequential substitutions Gauss-Seidel type for updating converter injected currents and supply harmonic voltages for harmonic analyses in power systems. Explicit reference is made to the Iterative Harmonic Analysis (IHA) in its classical formulation, even if the results obtained apply to a wider set of cases. Two proposed series compensation techniques to improve IHA convergence are described and their applicability limits are analyzed. To overcome the limits, a parallel compensation technique is presented. A critical case-study, characterized by the presence of AC system shunt resonances which result in the divergence of IHA, is solved and the results obtained by different compensation impedance values are analyzed and discussed. The paper shows that the parallel compensation technique succeeds in overcoming both the convergence problems of IHA and the intrinsic applicability limits of series compensation techniques, also in presence of AC systems with critical shunt resonances.