There is a strong trend in the photovoltaic inverter technology to use transformerless topologies in order to acquire higher efficiencies combining with very low ground leakage current. In this ...paper, a new topology, based on the H-bridge with a new ac bypass circuit consisting of a diode rectifier and a switch with clamping to the dc midpoint, is proposed. The topology is simulated and experimentally validated, and a comparison with other existing topologies is performed. High conversion efficiency and low leakage current are demonstrated.
The economic viability of renewable energy generation is vital for sustainability. Ensuring that optimal operation is always achieved, using energy management systems and control algorithms, is ...essential in this endeavor. Here, a new real-time pricing scheme, the Danish flexible pricing scheme, illustrates how residential PV and battery systems can optimize the electricity bill of households, without changing consumption behavior or providing grid services in exchange. This means that the only addition is PV production, storage, and control. A case study is constructed from Danish household consumption data, irradiance measurements, and recorded spot prices. With the input data, the pricing scheme, and the energy flow, simulation models are computed in MATLAB, thereby validating the algorithmic potential and finding the best strategy for charging and discharging the energy storage unit. Different methods are compared to list the viable options and evaluate them, based on the economic feasibility for the household. Furthermore, a discussion of the system implementation is also included to highlight technical difficulties, co-integration opportunities, short-comings, and advantages present in the case study. In conclusion, it is possible to make renewable energy generation, and storage, viable for a Danish residential household under the new pricing scheme.
A megújuló energia az egyik legmegfelelőbb megoldás a tiszta energia előállítására. A szél- és napenergia-berendezések hatalmas növekedést értek el az elmúlt évtizedekben, és a jövőben a fő ...energiatermelési technológiává válnak, megszüntetve a klasszikus energiatermelést, mint a szén és a gáz, amelyek a szén-dioxid és más üvegházhatású gázok kibocsátásának növekedését eredményezik. Ez a cikk áttekintést ad arról, hogy a hálózatra kapcsolt megújuló energiarendszerek, mint például a fotovoltaikus rendszerek, hogyan játszhatnak fontos szerepet a jövő energiaellátásában. Azt is mutatja, hogy az ilyen megújuló energiaforrásokat a tárolással kombinálni kell, hogy megfeleljenek a hálózati előírásoknak, és zölddé, valamint biztonságossá tegyék a jövő energiarendszerét.
CGE is a well‐established separation technique for the analysis of biologically important molecules such as nucleic acids. The inherent high resolving power, rapid analysis times, excellent detection ...sensitivity, and quantification capabilities makes this method favorable compared to conventional manual polyacrylamide and agarose slab gel electrophoresis techniques. In this paper we introduce a novel single‐channel capillary gel electrophoresis system with LED‐induced fluorescence detection also utilizing a compact pen‐shaped capillary cartridge design for automatic analysis of samples from a 96‐well plate. To evaluate the suitability of the system, 1000 genomic DNA(gDNA) samples were analyzed in gel filled capillaries and detected by the microball ended excitation and emission optical fiber based LED‐induced fluorescence detection system. Excellent migration time reproducibility of RSD <0.75% was obtained over the course of 1000 runs. The system rapidly distinguished between intact and degraded gDNA samples, therefore provided important information if they could be used for downstream quantitative PCR processing where high‐quality intact gDNA was key. We envision that this novel system design will rapidly find new applications in both research and clinical diagnostic laboratories as a highly sensitive and easy to use bio‐analytical approach.
This paper analyzes and compares three transformerless photovoltaic inverter topologies for three-phase grid connection with the main focus on the safety issues that result from the lack of galvanic ...isolation. A common-mode model, valid at frequencies lower than 50 kHz, is adopted to study the leakage current paths. The model is validated by both simulation and experimental results. These will be used to compare the selected topologies, and to explain the influence of system unbalance and the neutral conductor inductance on the leakage current. It will be demonstrated that the later has a crucial influence. Finally, a comparison of the selected topologies is carried out, based on the adopted modulation, connection of the neutral and its inductance, effects of unbalance conditions, component ratings, output voltage levels, and filter size.
► Simultaneous haplotyping of two miRNA-binding sites in the WSF1 is presented. ► A combination allele-specific amplification and capillary electrophoresis was used. ► Ultra-fast size determination ...of the generated PCR fragments was done by CGE. ► Excellent detection limit of 2ng/ml was demonstrated.
The transmembrane protein wolframin (WSF1) plays a crucial role in cell integrity in pancreatic beta cells and maintaining ER homeostasis. Genetic variations in the WFS1 gene have been described to be associated with Wolfram syndrome or type 2 diabetes mellitus. In this paper we report on an efficient double-tube allele-specific amplification method in conjunction with ultrafast capillary gel electrophoresis for direct haplotyping analysis of the SNPs in two important miRNA-binding sites (rs1046322 and rs9457) in the WFS1 gene. An automated single-channel capillary gel electrophoresis system was utilized in the method that provided dsDNA fragment analysis in less than 240s. The light-emitting diode induced fluorescence (LEDIF) detection system enabled excellent sensitivity for automated haplotyping of a large number of clinical samples. The detection limit was 0.002ng/μL using field amplified injection from water diluted samples. The dynamic quantitation range was 0.08–10.00ng/μL (R2=0.9997) in buffer diluted samples.
The penetration of solar energy in the modern power system is still increasing with a fast growth rate after long development due to reduced environmental impact and ever-decreasing photovoltaic ...panel cost. Meanwhile, distribution networks have to deal with a huge amount and frequent fluctuations of power due to the intermittent nature of solar energy, which influences the grid stability and could cause a voltage rise in the low-voltage grid. In order to reduce these fluctuations and ensure a stable and reliable power supply, energy storage systems are introduced, as they can absorb or release energy on demand, which provides more control flexibility for PV systems. At present, storage technologies are still under development and integrated in renewable applications, especially in smart grids, where lowering the cost and enhancing the reliability are the main tasks. This study reviews and discusses several active power control strategies for hybrid PV and energy storage systems that deliver ancillary services for grid support. The technological advancements and developments of energy storage systems in grid-tied PV applications are also reviewed.
This study proposes a common grounded Z-source DC–DC converter. In comparison to conventional Z-source converter, it converts voltage with higher voltage gain and lower voltage stress on the switch, ...diodes and capacitors. In addition, it needs smaller inductors in comparison to the similar converters. The converter is analysed and compared with other converters. Its main equations are obtained which show the converter advantages as lower voltage stresses, smaller inductors, higher efficiency and higher voltage gain in comparison to the reviewed converters. A prototype for the proposed converter is prepared based on analysis and theoretical parts. Experiments are done along the lines of the analysis. Experimental results and theoretical equations are used to prove the converter operation quality.
Nowadays, the penetration of inverter-based energy resources is continuously increasing in low-voltage distribution grids. Their applications cover traditional renewable energy production and energy ...storage but also new applications such as charging points for electric vehicles, heat pumps, electrolyzers, etc. The power ratings range from a couple of kW to hundreds of kW. Utilities have, in the last few years, reported more challenges regarding power quality in distribution grids, e.g., high harmonic content, high unbalances, large voltage and frequency excursions, etc. Phase-Lock-Loop (PLL) algorithms are typically used for grid synchronization and decoupled control of power converters connected to the grid. Most of the research within PLLs is mainly focusing on grid voltage angle estimation while the byproducts of the algorithms, e.g., frequency and voltage magnitude, are often overlooked. However, both frequency and voltage magnitude estimations are crucial for grid code compliance. Practical considerations for implementation on microcontroller boards of these algorithms are also missing in most of the cases. The present paper proposes a modified PLL algorithm based on a Synchronous Reference Frame that is suitable for both grid synchronization and frequency monitoring, i.e., the estimation of RMS phase voltages and frequencies in highly distorted distribution grids. It also provides the tuning methodology and practical considerations for implementation on commercial DSP boards. The performance of the proposed approach is assessed through simulation studies and laboratory tests under a wide range of operational conditions, showing that the proposed PLL can estimate the grid frequency, for all considered grid events, with an accuracy of less than ±5 mHz, which is a significant improvement on the current state-of-the-art solutions, having an accuracy of at least ±20 mHz or more.
Power ramp limitation (PRL) is likely to become a requirement for large-scale photovoltaic power plants (LPVPPs) in order to allow the increase of PV penetration levels. Especially in islands with ...reduced inertia capability, this problem is more stringent: high-power ramp can be caused by either fast irradiance changes or other participant generators for example wind power, or loads. In order to compensate for the power mismatch, LPVPPs must use active power reserve (APR), by either curtailment or auxiliary storage. The paper proposes a PRL control structure for dynamic APR sizing and deployment. The selected test case is the power system of Puerto Rico (PREPA), modeled using the modified IEEE 12 bus benchmark system, with different levels of PV penetration. It is shown that LPVPP with PRL can effectively reduce the ramping rate of the participating generators. Considering that the large area of LPVPPs acts as a filter against fast irradiance changes, the study also reveals the required plant size for which an auxiliary storage is no longer needed in order to comply with PRL requirements-an important economical aspect.
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