Dual Sequence Controller with Delayed Signal Cancellation in the Rotating Reference Frame

Manuscript submitted to the Twenty-second IEEE Workshop on Control and Modeling for Power Electronics (COMPEL 2021).<div>Abstract: Dual-sequence current controllers of voltage source converters (VSCs) feature two separate rotating reference frames (RRFs), commonly named dq frames, and rely on techniques that isolate the positive and negative sequences of three-phase measurements. One of these techniques is the delayed signal cancellation (DSC). It is performed in the stationary reference frame (SRF), also known as αβ frame. The DSC combines old values of one axis with new values of the other axis of the SRF. The results are, then, transformed into the RRFs for use in the current controller. This filtering process introduces an extra layer of complexity for dual-sequence current controllers, which could otherwise operate solely in the RRFs. This paper introduces a frequency adaptive DSC method that operates directly in the RRF. Moreover, an averaging of two of the proposed DSC filters with contiguous integer delays is employed for reducing discretization errors caused by grid frequency excursions. A formal proof of the equivalence between the αβ and dq DSC methods is presented. Furthermore, computer simulations of a case study support the interpretation of the results.</div>

Dual Sequence Controller with Delayed Signal Cancellation in the Rotating Reference Frame

Manuscript submitted to the Twenty-second IEEE Workshop on Control and Modeling for Power Electronics (COMPEL 2021).<div>Abstract: Dual-sequence current controllers of voltage source converters (VSCs) feature two separate rotating reference frames (RRFs), commonly named dq frames, and rely on techniques that isolate the positive and negative sequences of three-phase measurements. One of these techniques is the delayed signal cancellation (DSC). It is performed in the stationary reference frame (SRF), also known as αβ frame. The DSC combines old values of one axis with new values of the other axis of the SRF. The results are, then, transformed into the RRFs for use in the current controller. This filtering process introduces an extra layer of complexity for dual-sequence current controllers, which could otherwise operate solely in the RRFs. This paper introduces a frequency adaptive DSC method that operates directly in the RRF. Moreover, an averaging of two of the proposed DSC filters with contiguous integer delays is employed for reducing discretization errors caused by grid frequency excursions. A formal proof of the equivalence between the αβ and dq DSC methods is presented. Furthermore, computer simulations of a case study support the interpretation of the results.</div>

A characterization of Riesz-dual sequences which are near-Markushevich bases

The concept of Riesz-duals of a frame is a recently introduced concept with broad implications to frame theory in general, as well as to the special cases of Gabor and wavelet analysis. In this paper, we introduce various alternative Riesz-duals, with a focus on what we call Riesz-duals of type I and II. Next, we provide some characterizations of Riesz-dual sequences in Banach spaces. A basic problem of interest in connection with the study of Riesz-duals in Banach spaces is that of characterizing those Riesz-duals which can essentially be regarded as M-basis. We give some conditions under which an Riesz-dual sequence to be an M-basis for [Formula: see text].

A Synchronization Acquisition Method for the Dual-Sequence-Frequency-Hopping Communication System Based on Software Defined Radio at Low SNR

The Dual-Sequence-Frequency-Hopping (DSFH) communication system based on software defined radio (SDR) system belongs to the field of information and communication security of software engineering. At very low signal-to-noise ratio (SNR), which is lower than -10dB, the DSFH fails to synchronize. Synchronization acquisition method via a combined multi-signal detection (SAMCMD) is proposed. The feature of a short sequence of frequency hopping (FH) frequency point is utilized to express the information of the time of date (TOD), and the time accumulation of several FH signals is used to extend the detection time. This method can not only be appropriate for DSFH but also greatly improve the synchronization performance at low SNR. Explain the principle and structure of the SAMCMD. And obtain the performance of this method of the SDR synchronization acquisition. The conclusions are as below: 1) the longer detection time is, the better the anti-jamming performance of SAMCMD is; 2) SAMCMD can gain about 22.5dB-24dB when the SNR is -20dB and the acquisition probability requirement is 96.31% due to the extension of the detection time, compared with the traditional FH synchronization acquisition method.

A dual sequence and culture-based survey of maize rhizosphere protists reveals dominant, plant-enriched, and culturable community members

Protists play important roles in shaping the microbial community of the rhizosphere. However, there is still a limited understanding of how plants shape the protist community, and how well protist isolate collections might represent rhizosphere protist composition and function in downstream studies. We sought to determine whether maize roots select for a distinct protist community in the field, and whether the common or dominant members of that community are readily culturable using standard protist isolation methods. We sequenced 18S and 16S rRNA genes from the rhizospheres of maize grown in two sites, and isolated 103 protists into culture from the same roots. While field site had the greatest effect, rhizospheres in both sites had distinct protist composition from the bulk soils, and certain taxa were enriched in both sites. Enriched taxa were correlated to bacterial abundance patterns. The isolated protists represented six supergroups, and the majority corresponded to taxa found in the sequencing survey. Twenty-six isolates matched eight of the 89 core rhizosphere taxa. This study demonstrates that maize roots select for a distinct protist community, but also illustrate the potential challenges in understanding the function of the dominant protist groups in the rhizosphere.

IrAAC-based construction of dual sequence-defined polytriazoles

One novel dual sequence-defined polytriazole structure was demonstrated here, which could be easily achieved through a two-step iterative sequential growth strategy involving azidation and iridium-catalyzed azide-alkyne cycloaddition (IrAAC) reaction. The...