When distributed generators are connected to the grid, it is required that the system withstand the voltage dip caused by the grid failure. This is known as the low voltage ride through (LVRT). One ...of the effective choices to realize the LVRT is a grid connected inverter with virtual synchronous generator (VSG). This paper present a VSG control with capability for LVRT. By using this control, the operation of inverter can be continued even if a severe voltage dip at the grid has happened.
The power capacity of distributed generators such as photovoltaic and wind turbine is growing, many of distributed generators are connected to a grid by inverters. The inverters are controlled by a ...PLL (Phase Locked Loop) in order to be synchronized with power system frequency. Power system will become unstable, if the capacity of inverter-connected-type distributed generators becomes larger and larger, because inverter frequency is controlled to follow the grid frequency. The concept of "Virtual Synchronous Generator" (VSG), which is to control inverters to behave like a synchronous generator, has been proposed. VSG has virtual inertia which is realized by an energy storage device to pretend rotor's inertia. In this paper, the control scheme of VSG is investigated which is based on the swing equation of a synchronous generator. Numerical simulation results show both ride-through capability of voltage dip and enhancement ability of grid stability.
The previous quantum mechanical close-coupling study of the dissociative collisions in He + H
2 (T-shape configuration) by the present authors Chem. Phys. Letters 216 (1993) 613 has been extended to ...a wide range of the total energy 4.8-7.5 eV. The dissociation process shows a clear vibrational enhancement. The dissociation probability has an undulation as a function of the total energy, and by using classical S-matrix theory it is shown that this feature is caused by interference of the contributions of multiple trajectories.
When a greatly varying load is connected to a weak system, stability of the system becomes a problem. In these days, because the use of renewable energy is accelerating, not only the loads but also ...the distributed power sources can be critical factors in destabilizing the system. The virtual synchronous generator (VSG) control allows a static inverter to behave similar to a synchronous generator (SG). Using this VSG technology, we can decrease the introduction ratio of SGs with fossil fuels, and thus, we can combine various types of power sources. At the same time, if the combination of governor and rotor inertia is represented in a first-order lag element, the VSG can suppress the frequency fluctuations in microgrids. In this paper, we present a design guideline of a VSG. The simulation results by EMTP-RV confirmed that the parallel-connected VSG can suppress the frequency fluctuation. In addition, the results were almost consistent with the experimental test results.
The rise of inorganic-biological hybrid organisms for solar-to-chemical production has spurred mechanistic investigations into the dynamics of the biotic-abiotic interface to drive the development of ...next-generation systems. The model system, Moorella thermoacetica-cadmium sulfide (CdS), combines an inorganic semiconductor nanoparticle light harvester with an acetogenic bacterium to drive the photosynthetic reduction of CO^sub 2^ to acetic acid with high efficiency. In this work, we report insights into this unique electrotrophic behavior and propose a charge-transfer mechanism from CdS to M. thermoacetica. Transient absorption (TA) spectroscopy revealed that photoexcited electron transfer rates increase with increasing hydrogenase (H^sub 2^ase) enzyme activity. On the same time scale as the TA spectroscopy, time-resolved infrared (TRIR) spectroscopy showed spectral changes in the 1,700-1,900-cm^sup -1^ spectral region. The quantum efficiency of this system for photosynthetic acetic acid generation also increased with increasing H2ase activity and shorter carrier lifetimes when averaged over the first 24 h of photosynthesis. However, within the initial 3 h of photosynthesis, the rate followed an opposite trend: The bacteria with the lowest H^sub 2^ase activity photosynthesized acetic acid the fastest. These results suggest a two-pathway mechanism: a high quantum efficiency charge-transfer pathway to H^sub 2^ase generating H^sub 2^ as a molecular intermediate that dominates at long time scales (24 h), and a direct energy-transducing enzymatic pathway responsible for acetic acid production at short time scales (3 h). This work represents a promising platform to utilize conventional spectroscopic methodology to extract insights from more complex biotic-abiotic hybrid systems.
We investigated the effects of indium doping on the superconducting properties of YBCO sintered samples and thin films. In sub(2)O sub(3)-doped YBCO and YBa sub(2)Cu sub(3-x)In sub(x)O sub(y) ...sintered samples showed a gradual decrease in the critical temperature (T sub(c)) with increasing indium content; however, a T sub(c) value above 80 K was maintained even up to 30 vol.% addition and x = 0.4, respectively. Ba sub(3)Cu sub(3)In sub(4)O sub(12) was detected by X-ray diffractometry and energy-dispersive X-ray spectroscopy as a reaction product for both sintered samples. The normalized J sub(c) under a magnetic field of 0.1 T showed a maximum at x = 0.3. Indium-doped YBCO films prepared by pulsed laser deposition showed a similar dependence of T sub(c) on indium content as the sintered samples.
Peak E substance, a trace impurity in L-tryptophan, has been associated epidemiologically with an outbreak of eosinophilia-myalgia syndrome (EMS) in the USA in 1989. After fractionation and ...purification of this substance, nuclear magnetic resonance and fast-atom-bombardment mass spectroscopy were used to identify the molecular structures of peak X/X' (formed by the decomposition of peak E substance in a simulated gastric fluid) and peak Y/Y' substances (which are believed to be the intermediates in the transformation of peak E substance to peak X/X' substances). The analyses were also performed on synthesized peak E substance obtained from the reaction of tryptophan with acetaldehyde. The results indicated that the synthesized substance was of high purity and was suitable for use in studies investigating the relationship between peak E substance and EMS onset.
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