Iterative Time-Frequency Harmonic Analysis: Problems and Solutions

This work discusses some characteristics of iterative harmonic analysis using interfaced electromagnetic transients and harmonic power flow programs. This approach allows combining the advantages of both program types. However, some problems arise, such as harmonic estimation inaccuracy and convergence issues, the first being originated by mis-synchronization, spectral leakage and picket-fences. These problems are highlighted in the present paper, and an application example is presented, in which two types of Flexible AC Transmission controllers, Thyristor Controlled Reactors and Static VAR Compensator, are included into the IEEE 14 bus system. The developed FFT-based algorithm, complying with IEC 61000, is evaluated, and it proves being adequate to avoid spectral leakage and picket-fences. Some alternatives to overcome convergence problems are presented.