Browsing by Keyword "Modular multilevel converter"
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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 Reliable Modular Multilevel Converter Fault Detection with Redundant Voltage Sensor(2017-01) Picas, Ricard; Zaragoza, Jordi; Pou, Josep; Ceballos, Salvador; POWER ELECTRONICS AND SYSTEM EQUIPMENTThis paper presents a fault-tolerant configuration for the modular multilevel converter (MMC). The procedure is able to detect faults in voltage sensors and semiconductor switching devices, and it can reconfigure the system so that it can keep on operating. Both switch and sensor faults can be detected by comparing the output voltage of a set of submodules (SMs), which is measured by a so-called supervisory sensor, with two calculated reference voltages. Faults in the supervisory sensors are also considered. Sensor faults are overcome by using a measuring technique based on estimates that are periodically updated with the voltage measurements of the supervisory sensors. Additional SMs are included in the arms so that the MMC can bypass a faulty SM and continue operating without affecting the output voltage of the phase-leg. Experimental results obtained from a low-power MMC prototype are presented in order to demonstrate the effectiveness of the proposed techniques.