Browsing by Keyword "multilevel converters"
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Item Control of Circulating Currents in Modular Multilevel Converters Through Redundant Voltage Levels(2016-11) Konstantinou, Georgios; Pou, Josep; Ceballos, Salvador; Picas, Ricard; Zaragoza, Jordi; Agelidis, Vassilios G.; POWER ELECTRONICS AND SYSTEM EQUIPMENTAmong the main control targets in a modular multilevel converter (MMC) is the control of the circulating currents within the phase legs of the topology. This paper presents a controller for the circulating current of the MMC that utilizes the available redundancies of the multilevel waveform in 2N+1 modulated MMCs in order to regulate the circulating current to its reference. The main advantages of the approach are the elimination of control loops that generate the reference voltages for the control of the circulating current, simple implementation and very fast dynamic performance. The controller is implemented at the modulation stage and its operation is independent of the circulating current reference. An extension of the controller to track large deviations in the circulating current is also demonstrated. The simplicity and effectiveness of the proposed controller is illustrated through detailed simulations and experimental results from a single-phase laboratory prototype.Item Interleaved Operation of Three-Level Neutral Point Clamped Converter Legs and Reduction of Circulating Currents under SHE-PWM(2016-06) Konstantinou, Georgios; Pou, Josep; Capella, Gabriel J.; Song, Kejian; Ceballos, Salvador; Agelidis, Vassilios G.; POWER ELECTRONICS AND SYSTEM EQUIPMENTInterleaving of voltage-source converter (VSC) legs enables higher output currents per phase, effectively increasing the power rating without increasing semiconductor ratings. However, the interleaved operation results in circulating currents between each phase converter legs as well as a zero-sequence circulating current (ZSCC), which become quite prominent when the converters operate with low switching frequencies. This paper demonstrates the interleaved operation of three-level converters under selective harmonic elimination pulsewidth modulation (SHE-PWM). A controller for the circulating current within the legs of each phase is also proposed. The controller is used in combination with optimally selected SHE-PWM patterns to generate the maximum number of voltage levels and minimize the peak value of the circulating current. Simulation and experimental results show the interleaved operation and the effect of SHE-PWM pattern selection in the overall system.