Control and analysis of a unified power flow controller

This paper presents a control scheme and comprehensive analysis for a unified power flow controller (UPFC) on the basis of theory, computer simulation and experiment. This developed theoretical analysis reveals that a conventional power feedback control scheme makes the UPFC induce power fluctuation in transient states. The conventional control scheme cannot attenuate the power fluctuation, and so the time constant of damping is independent of active and reactive power feedback gains integrated in its control circuit. This paper proposes an advanced control scheme which has the function of successfully damping out the power fluctuation. A UPFC rated at 10 kVA is designed and constructed, which is a combination of a series device consisting of three single-phase pulsewidth modulation (PWM) converters and a shunt device consisting of a three-phase diode rectifier. Although the dynamics of the shunt device are not included, it is possible to confirm and demonstrate the performance of the series device. Experimental results agree well with both analytical and simulated results and show viability and effectiveness of the proposed control scheme </p

Zero dimensional Gorenstein algebras with the action of the symmetric group SkS_k

We consider irreducible decompositions of certain Artinian algebras with the action of the symmetric group. The equi-degree monomial complete intersection can be thought of as a k-fold tensor of an n dimensional vector space. Otherwise put the tensor space can be given a commutative ring structure. From this view point we show that, in the case n=2 or k=2, the strong Lefschetz property can be used efficiently to decompose the algebra into irreducible components. We apply the result to determin a minimal generating set of certain Gorenstein ideal. Also we show that the Hilbert function of certain ring of invariants is a q-anolog of the binomial coefficent

Upper Crustal Structure in the Northwestern Chubu District, Japan as Derive d from the Tedori-River Quarry Blasts.

The upper crustal structure in the northwestern Chubu region has been investigated from a number of quarry blasts at the Tedori-River Dam site, Ishikawa Prefecture. For effective observations of seismic waves from the blasts, mobile observations have been carried out during four months from May to August, 1978, at 107 sites including permanent stations along 14 profiles extending radially from the quarry site to a distance of about 150 kilometers. The results reveal some gaps in the travel-time-distance relations and regional irregularities in the apparent velocities, suggesting complicated structures in the upper crust over this region. Since most of the profiles have not been covered by reverse observations, two different simple layered models are tentatively proposed here. These are Model II, with two layers, 1st layer : 5.3km/sec (0≦H<2.5km) 2nd layer : 6.15km/sec (2.5≦H km) and Model III with three layers, 1st layer : 5.0km/sec (0≦H<0.5km) 2nd layer : 5.6km/syc (0.5≦H<4.0km) 3rd layer : 6.4km/sec (4≦H km) Spatial distribution of the differences between the observed travel times and the corresponding times calculated for Model II show that in the coastal area of the Sea of Japan there exists a low-velocity surface layer with a time delay of the order of 0.5 seconds. Lateral heterogeneities in the structure should be taken into consideration in investigating seismic activities in this region

Transient analysis of a unified power flow controller and its application to design of the DC-link capacitor

This paper presents a transient analysis of a unified power flow controller (UPFC), and design of capacitance of the dc-link capacitor based on that analysis. Active power flowing out of the series device in transient states is theoretically discussed to derive what amount of electric energy the dc link capacitor absorbs or releases through the series device. As a result, it is clarified that the active power flowing out of the series device is stored in the line inductance as magnetic energy during transient states. Design of capacitance of the dc-link capacitor is also presented in this paper, based on the theoretical analysis. Experimental results obtained from a 10-kVA laboratory setup are shown to verify the analytical results.</p

Structural diversity and evolution of the N-terminal isoform-specific region of ecdysone receptor-A and -B1 isoforms in insects

<p>Abstract</p> <p>Background</p> <p>The ecdysone receptor (EcR) regulates various cellular responses to ecdysteroids during insect development. Insects have multiple EcR isoforms with different N-terminal A/B domains that contain the isoform-specific activation function (AF)-1 region. Although distinct physiologic functions of the EcR isoforms have been characterized in higher holometabolous insects, they remain unclear in basal direct-developing insects, in which only A isoform has been identified. To examine the structural basis of the EcR isoform-specific AF-1 regions, we performed a comprehensive structural comparison of the isoform-specific region of the EcR-A and -B1 isoforms in insects.</p> <p>Results</p> <p>The EcR isoforms were newly identified in 51 species of insects and non-insect arthropods, including direct-developing ametabolous and hemimetabolous insects. The comprehensive structural comparison revealed that the isoform-specific region of each EcR isoform contained evolutionally conserved microdomain structures and insect subgroup-specific structural modifications. The A isoform-specific region generally contained four conserved microdomains, including the SUMOylation motif and the nuclear localization signal, whereas the B1 isoform-specific region contained three conserved microdomains, including an acidic activator domain-like motif. In addition, the EcR-B1 isoform of holometabolous insects had a novel microdomain at the N-terminal end.</p> <p>Conclusions</p> <p>Given that the nuclear receptor AF-1 is involved in cofactor recruitment and transcriptional regulation, the microdomain structures identified in the isoform-specific A/B domains might function as signature motifs and/or as targets for cofactor proteins that play essential roles in the EcR isoform-specific AF-1 regions. Moreover, the novel microdomain in the isoform-specific region of the holometabolous insect EcR-B1 isoform suggests that the holometabolous insect EcR-B1 acquired additional transcriptional regulation mechanisms.</p