Browsing by Keyword "Selective harmonic elimination (SHE)"
Now showing 1 - 2 of 2
Results Per Page
Sort Options
Item Circulating Current Control for Modular Multilevel Converters with (N+1) Selective Harmonic Elimination - PWM(2020-08) Perez-Basante, Angel; Ceballos, Salvador; Konstantinou, Georgios; Pou, J.; Sanchez-Ruiz, Alain; Lopez, Iraide; Martinez de Alegria, Inigo; POWER ELECTRONICS AND SYSTEM EQUIPMENTModular multilevel converters (MMCs) require control of the circulating current, i_circ, to improve their operation and efficiency. This is particularly important when low switching frequency modulation techniques, such as selective harmonic elimination (SHE-PWM) are applied. This work provides a novel method to control the circulating current along with (N+1) SHE-PWM. Unlike the case of (2N+1) SHE-PWM, explicit redundant levels are not available and, therefore, different modulation indexes, m_1 and m_2, are employed in the upper and lower arms to obtain the desired modulation index m_a. Unlike previous (N+1) circulating current methods, the distances between m_a, m_1 and m_2 remain constant to not disturb the phase output voltage, with an interchange of m_1 and m_2 between the arms used to follow the desired i_circ. The control adjusts the dc component of the circulating current and the energy stored in the SMs to their references, while maintaining the energy balance between the upper and lower arms. Simulation tests and experimental results, obtained from a single-phase laboratory prototype MMC, validate the proposed control technique.Item A universal formulation for selective harmonic elimination PWM with half-wave symmetry for multilevel voltage source converters(IEEE Computer Society, 2016-12-21) Perez-Basante, Angel; Ceballos, Salvador; Konstantinou, Georgios; Pou, Josep; Andreu, Jon; De Alegría, Íñigo Martinez; POWER ELECTRONICS AND SYSTEM EQUIPMENTSelective harmonic elimination (SHE) - pulse with modulation (PWM), when applied to multilevel converters (MCs), can be optimized in case a half-wave (HW) symmetry is implemented. This kind of symmetry is able to provide a wide variety of solutions. This paper proposes a novel method, based on optimization algorithms, which provides a universal formulation of the SHE-PWM problem with HW symmetry, in such a way that different equation systems are not required to find a solution when different switching patterns are considered. In this way, the proposed technique is able to search simultaneously both the switching patterns and their associated firing angles that solve the SHE-PWM problem, without using predefined waveforms. Therefore, the search process is significantly simplified and the flexibility to find solutions with different waveforms, throughout the reference modulation index, ma, range, is increased. Different sets of solutions provided by this method have been presented and simulation results, obtained from a five-level modular multilevel converter (MMC), have proved the validity of the new proposed technique.