Browsing by Keyword "pulse width modulated inverters"
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Item Elimination of Low-Frequency Ripples and Regulation of Neutral-Point Voltage in Stacked Multicell Converters(2017-01) Ghias, Amer M.Y.M.; Pou, Josep; Acuna, Pablo; Ceballos, Salvador; Heidari, Alireza; Agelidis, Vassilios G.; Merabet, Adel; POWER ELECTRONICS AND SYSTEM EQUIPMENTThis paper introduces a modulation method for the stacked multicell converters (SMCs). The proposed method is implemented using phase-disposition pulse width modulation and is capable of balancing and regulating the voltages of all the capacitors in the topology, i.e., the flying capacitors and the dc-link capacitors. The proposed method is also able to eliminate the low-frequency voltage ripples that may appear in the neutral point (NP) of SMCs. In SMCs with two stacks, the NP voltage level can be generated by direct connection of the output to the dc-link NP, but also using two extra states available. This redundancy is used to regulate the NP voltage. Furthermore, since the proposed method can eliminate the low-frequency voltage ripples in the capacitors, the capacitances of all the capacitors of the SMCs can be reduced, while maintaining high quality of the output voltages and currents. This enables the use of film capacitors. Simulation and experimental results are presented from a three-phase five-level 2× 2 SMC to verify the effectiveness of the proposed method.Item Modulation Strategy for Multiphase Neutral-Point-Clamped Converters(2016-02-01) Lopez, Iraide; Ceballos, Salvador; Pou, Josep; Zaragoza, Jordi; Andreu, Jon; Kortabarria, Iñigo; Agelidis, V.G.; POWER ELECTRONICS AND SYSTEM EQUIPMENTThis paper presents a novel modulation strategy for n-phase neutral-point-clamped (NPC) converters. The proposed modulation strategy is able to control and completely remove the low-frequency neutral-point (NP) voltage oscillations for any operation point and load types. Even when unbalanced and/or nonlinear loads are considered, the NP voltage remains under total control. Consequently, the strategy is very attractive for n-phase active filters. In addition, it enables the use of low-capacity film capacitors in NPC converters. The proposed modulation takes the carrier-based modulation strategy as a basis. It is formulated following a generalized approach that makes it expandable to n-phase NPC converters. In addition, the NP voltage is controlled directly using a closed-loop algorithm that does not rely on the use of the linear control regulators or the additional compensators used in other modulation algorithms. Therefore, no tuning of parameters is required and it performs optimally for any operating conditions and kind of loads, including unbalanced and nonlinear loads. Although the high-frequency harmonic content of the output voltages may increase, the weighted total harmonic distortion generated by the proposed strategy is similar to that of a standard sinusoidal pulse width modulated strategy. The proposed modulation algorithm has been tested in a four-leg NPC converter prototype performing as a three-and four-phase system and operating with balanced and unbalanced loads.