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Commutation failure is one of the most important factors threatening the safety of multi-infeed high voltage direct current systems. To mitigate commutation failure, we have proposed a novel hybrid line-commutated converter by adding fully controlled devices to the conventional line-commutated converter. It aims to achieve auxiliary commutation and forced commutation with the help of fully controlled devices. Based on the novel hybrid line-commutated converter topology, the study investigates how to select suitable fully controlled devices and how to design the appropriate parameters of the devices. First, this article studied the general characteristics of reverse-blocking devices, including reverse-blocking integrated gate-commutated thyristor (RB-IGCT) and asymmetrical IGCT with diode (including fast recovery diode and standard recovery diode). Then, the novel commutation principle is carefully proposed and analyzed. The comprehensive simulation results and comparison study of the novel commutation principle are conducted. Then, according to the proposed commutation principle, the voltage and current working stress of devices are illustrated. According to these, vital features of devices, including recovery speed, on-state voltage, current conduction ability, surge current, maximum turn-off current, robustness, and volume of devices, are carefully analyzed and compared. Related experiments are conducted to present the vital characteristics of devices in the equivalent operating conditions in converters. Finally, the advantages and disadvantages of RB-IGCT and IGCT with fast recovery diode and standard recovery diode are comprehensively presented, which offers valuable reference considered in engineering applications. [ABSTRACT FROM AUTHOR]

Recently, switched inductor (SI) and switched capacitor techniques in dc–dc converter are recommended to achieve high voltage by using the principle of parallel charging and series discharging of reactive elements. It is noteworthy that four diodes, one high-voltage rating switch, and two inductors are required to design classical SI boost converter (SIBC). Moreover, in classical SIBC, the switch voltage stress is equal to the output voltage. In this article, modified SIBC (mSIBC) is proposed with reduced voltage stress across active switches. The proposed mSIBC configuration in this article is transformerless and simply derived by replacing the one diode of the classical SI structure with an active switch. As a result, mSIBC required low-voltage rating active switches, since the total output voltage is shared into two active switches. Moreover, the proposed mSIBC is low in cost, provides higher efficiency, and requires the same number of components compared with the classical SIBC. The continuous conduction mode and discontinuous conduction mode analysis, the effect of nonidealities on voltage gain, design methodology, and comparison are presented in detail. The operation and performance of the designed 500-W mSIBC are experimentally validated under different perturbations. [ABSTRACT FROM AUTHOR]

One of the most important power quality issues is related to current harmonics generated by nonlinear loads such as diode and thyristor front-end rectifiers. Well-established solutions to overcome this problem, such as active power filters (APFs), have the required high power rating components as a major disadvantage. An alternative, called hybrid power filter (HPF), mixes low power rating active filters with passive filters. Unfortunately, many of these HPF topologies have, as a common disadvantage, a great number of passive components and/or transformers. Based on this fact, new concepts of HPFs, consisting of small-rated inverters and $LC$ filters, have been introduced with wide acceptance. The advantage comes from the fact that these HPFs are connected to the grid without any matching transformer. Recently, some topologies based on dual-converter configurations have been shown to be very attractive, where the APF (or HPF) must deal with highly nonlinear loads with high values of $di/dt$ and supplying the reactive power together with harmonic compensation. On the other hand, the drawback of dual converters is the high number of switch devices. Therefore, this paper proposes a transformerless HPF based on a new six-switch two-leg inverter with an enhanced harmonic compensation capability. Aside from presenting a reduced number of switches when compared with dual topologies, the proposed solution is capable of providing fully compensation even for loads with high harmonic content. Experimental results are presented for an HPF inverter prototype in order to demonstrate that the harmonic compensation performance meets the IEEE 519 standard. [ABSTRACT FROM PUBLISHER]