Selective harmonic elimination method for unequal DC sources of multilevel inverters

Abstract

This paper presented an analytical and closed-form solution for the harmonic contents that were injected in the five-level inverters from asymmetrical DC sources or batteries which were suitable for renewable energy sources. In the five-level inverters, two DC sources V 1 and V 2 were used to synthesize the output voltage. Therefore, two transcendental equations were formulated for the fundamental and the third harmonic orders based on the unequal DC sources V 1 and V 2 . These transcendental equations were solved analytically for low switching control technique. The proposed solution included the modulation index change which resulted in changing the fundamental component. Therefore, two switching angles are formulated and solved analytically to control the amplitude of the fundamental voltage and cancel the third order harmonic. A well-known third order equation was generated. Thus, a closed-form solution for the above two switching angles will be generated in terms of the modulation index. The proposed solution was tested for a wide range of V 1 /V 2 ratio. Some selected simulation and experimental results were provided to validate the proposed method for wide ranges of both modulation index and V 1 /V 2 ratio.

Low switching frequency modulation for generalized three-phase multilevel inverters geared toward Grid Codes compliance

“…Nowadays, there is only one well-established LSFM scheme geared toward grid-tied applications known as selective harmonic mitigation (SHM) which in turn is akin to the selective harmonic elimination (SHE) modulation technique [8]- [11]. However, SHE/SHM has some limitations that could be overcome by NLC [5], [12], especially those related to dynamic performance under real-time operation and computational effort required while using lookup tables or curve fitting polynomials or any initial guessing and iterative routines [13], [14].…”

Classical Control for Unequal DC Sources Five-Level Inverter-Based SHE Technique

“…On the other hand, real-time solution is adopted to track modulation index changes [17][18][19][20][21][22][23][24][25]. These proposed techniques will be discussed in detail, based on symmetrical/asymmetrical DC sources MLI and higher/lower order harmonic eliminations.…”

“…This phenomenon causes mismatches among their DC sources. Given that these DC sources are typically unequal, different control algorithms should be applied [24][25][26], which are explained in the following paragraphs. In [24], an artificial neural network (ANN)-based algorithm was introduced to calculate switching angles in real time for unequal DC sources.…”

“…The ANN can guarantee a fast response due to decreasing of time computation, but the output angles returned by the ANN may not provide a satisfactory result, or harmonic elimination, at some points as it generalizes. In [25], an analytical solution based on the cosine term identities for multiple angles was proposed for MLIs with asymmetrical DC sources. The nonlinear transcendental set of equations is transformed into a third-order equation with well-known solutions.…”

Modeling and control of 41-level inverter using best switching angles calculation method

“…In applied power engineering fields, the multilevel inverter used in many applications [7][8][9], there are three conventional categories of the multilevel inverters: cascaded H-bridge, neutral point clamped and flying capacitor multilevel inverter [10][11][12]. The multilevel inverter used for Induction heating, Traction systems, Active filtering, Motor drives, High-voltage and Medium-voltage applications [13][14].…”