Search

Three-phase phase-modular isolated power factor correction rectifiers are an interesting alternative to phase-integrated three-phase rectifiers as matrix-type phase modules allow a single-stage isolated energy conversion between the three-phase mains and a dc bus. Therefore, this paper presents a phase-modular isolated matrix-type rectifier which can be connected to the mains either in star (Y) or delta ( \Delta) configuration, enabling a wide input voltage range. Additionally this allows to select the voltage and current stresses of the phase module switches according to the used semiconductor technology, for example {\text{650 V}} Si or GaN devices could be used in rectifiers powered from the {400} or \text480 V\text{rms} mains. A detailed analysis of the operating principles and switching behavior of the converter is presented, showing that zero voltage switching can be achieved in the phase modules. Additionally a third harmonic current injection concept is proposed which allows an up to {15} \% higher output voltage in \Delta -mode. The concepts are validated with measurements taken on a {\text{7.5}}\;{\text{kW}}, {\text{400}}\;{\text{V}} dc output voltage prototype converter achieving 97.2 \% efficiency and a total harmonic distortion of < 2 \% at rated power. [ABSTRACT FROM AUTHOR]

As wind power technology points to increase power ratings, the implementation based on a permanent-magnet synchronous generator (PMSG) with a full-power converter is expanding its market share. Multilevel converters, as for example, neutral-point clamped (NPC) converters, are therefore well suited for this application. Predictive current control presents similar dynamic response and reference tracking than other well-established control methods, but working at lower switching frequencies, and providing extensive flexibility to apply either online or offline different control laws to the same plant. In this work, the predictive current control is applied to both sides of the back-to-back NPC converter connecting a permanent-magnet synchronous wind power generator to the grid. DC-link neutral-point balance is achieved by means of the predictive control algorithm, which considers the redundant switching states of the back-to-back NPC converter. Reduced number of commutations, current spectrum control, and compliance with the low-voltage ride-through (LVRT) requirement are carried out with the predictive control. The obtained experimental results confirm the suitability of the proposed control approach. [ABSTRACT FROM PUBLISHER]

This paper presents a generalized multilevel direct power control (ML-DPC) scheme for grid-connected multilevel power converters. The proposed method extends the original DPC operating principle by considering only the closest subset of two-level voltage vectors to the present switching state. The implementation of this principle requires the power derivatives for feedback, which can present numerical problems when applied experimentally, mainly due to high measurement noise sensitivity. Therefore, a derivative estimator is proposed based on the converter-grid model in the synchronous reference frame. In addition, a virtual flux observer is developed to achieve synchronization and improve robustness in the presence of grid voltage harmonics. The proposed method is applicable to any multilevel converter topology of any number of levels. In this paper, simulations and experimental results are presented for a seven-level cascaded H-bridge converter. [ABSTRACT FROM AUTHOR]