Novel calculation of HVDC converter harmonics by linearization in the time-domain

There is an increasing interest in the steady-state analysis of high power converter circuits for the computation of both characteristic and uncharacteristic harmonics. Uncharacteristic harmonics arise due to asymmetries in excitation/operation and are of particular interest given their overall adverse effect on the power system. Frequency domain methods for harmonic analysis are efficient though not necessarily comprehensive; that is not all the necessary details of the system are simultaneously modeled. This paper presents a novel technique that is both efficient and comprehensive as the time domain nature of the differential/algebraic equations describing the power converter operation is retained. Efficient convergence of the time domain boundary value problem is assured by an appropriate linearization. Subsequent Fourier analysis of the the time domain solution yields the harmonic spectra. Comparison is made with time domain steady-state solutions obtained by brute-force computation.