Power Drop Research Articles

Optimal real-time power dispatch of power grid with wind energy forecasting under extreme weather.

With breakthroughs in the power electronics industry, the stability and rapid power regulation of wind power generation have been improved. Its power generation technology is becoming more and more mature. However, there are still weaknesses in the operation and control of power systems under the influence of extreme weather events, especially in real-time power dispatch. To optimally distribute the power of the regulation resources in a more stable manner, a wind energy forecasting-based power dispatch model with time-control intervals optimization is proposed. In this model, the outage of the wind energy under extreme weather is analyzed by an autoregressive integrated moving average model (ARIMA). Additionally, the other regulation resources are used to balance the corresponding wind power drop and power mismatch. Meanwhile, an algorithm names weighted mean of vectors (INFO) is employed to solve the real-time power dispatch and minimize the power deviation between the power command and real output. Lastly, the performance of the proposed optimal real-time power dispatch is executed in a simulation model with ten regulation resources. The simulation tests show that the combination of ARIMA and INFO can effectively improve the power control performance of the PD-WEF system.

Effectiveness of Anodal otDCS Following with Anodal tDCS Rather than tDCS Alone for Increasing of Relative Power of Intrinsic Matched EEG Bands in Rat Brains.

This study sought to determine whether (1) evidence is available of interactions between anodal tDCS and oscillated tDCS stimulation patterns to increase the power of endogenous brain oscillations and (2) the frequency matching the applied anodal otDCS's frequency and the brain's dominant intrinsic frequency influence power shifting during stimulation pattern sessions by both anodal DCS and anodal oscillated DCS. Rats received different anodal tDCS and otDCS stimulation patterns using 8.5 Hz and 13 Hz state-related dominant intrinsic frequencies of anodal otDCS. The rats were divided into groups with specific stimulation patterns: group A: tDCS-otDCS (8.5 Hz)-otDCS (13 Hz); group B: otDCS (8.5 Hz)-tDCS-otDCS (13 Hz); group C: otDCS (13 Hz)-tDCS-otDCS (8.5 Hz). Acute relative power changes (i.e., following 10 min stimulation sessions) in six frequency bands-delta (1.5-4 Hz), theta (4-7 Hz), alpha-1 (7-10 Hz), alpha-2 (10-12 Hz), beta-1 (12-15 Hz) and beta-2 (15-20 Hz)-were compared using three factors and repeated ANOVA measurement. For each stimulation, tDCS increased theta power band and, above bands alpha and beta, a drop in delta power was observed. Anodal otDCS had a mild increasing power effect in both matched intrinsic and delta bands. In group pattern stimulations, increased power of endogenous frequencies matched exogenous otDCS frequencies-8.5 Hz or 13 Hz-with more potent effects in upper bands. The power was markedly more potent with the otDCS-tDCS stimulation pattern than the tDCS-otDCS pattern. The findings suggest that the otDCS-tDCS pattern stimulation increased the power in matched intrinsic oscillations and, significantly, in the above bands in an ascending order. We provide evidence for the successful corporation between otDCS (as frequency-matched guidance) and tDCS (as a power generator) rather than tDCS alone when stimulating a desired brain intrinsic band (herein, tES specificity).

Field study on the severity of photovoltaic potential induced degradation

Photovoltaic (PV) systems can be affected by different types of defects, faults, and mismatching conditions. A severe problem in PV systems has arisen in the last couple of years, known as potential-induced degradation (PID). During the early installation stage of the PV system, the PID may not be noticed because it appears over time (months or years). As time passes, it becomes more apparent since the output power may drop dramatically. We studied PV modules over the course of three years that were affected by PID. An electroluminescent and thermal imaging technique helped discover the PID. PID appeared in PV modules after being in different fields for 4–8 months, resulting in a 27–39% drop in power. An anti-PID box was fitted during the second year of the PV operation to recover the PID. Accordingly, it has stabilized the power degradation, but it could not restore the performance of the affected PID modules as compared with healthy/non-PID modules.

Effect of Fouling on the Performance of an Instream Turbine

As the tidal energy industry starts to mature towards commercial projects a key focus is on reliable power performance. As for any marine application, fouling poses a potential performance reduction risk for instream turbine deployments.
 SCHOTTEL HYDRO have developed their current commercial SCHOTTEL Instream Turbines. Four drivetrains with 6.3m rotors were deployed on the surface platform PLAT-I by Sustainable Marine Energy. One of PLAT-Is key features is access to the turbines for inspection and maintenance in situ. The system has undergone sea testing from 2017 to 2021 in Scotland and Nova Scotia (Canada).
 This paper presents the hydrodynamic rotor performance reduction due to fouling based on full-scale experimental results. An in-house blade element momentum model is used to quantify the changes of the hydrodynamic forces in terms of lift and drag for the hydrofoils used. Furthermore, the effect of fouling on the downstream wake was quantified in the field. The performance reduction due to fouling is significant and leads to a power drop of up to 43%, whereas the thrust is reduced by 25%. This is also reflected in a reduction of the turbine’s downstream wake as a “fouled” rotor extracts less energy from the flow. Modifications of the polar data, used for semi-empirical performance predictions, are able to predict the effect of fouling on the rotor performance.
 In general, the results derived from the testing prove the significance of access to the turbines in order to avoid reduction in the turbines’ performance due to fouling.

Effect of additional carrageenan concentration on the characteristics of wet noodles based on mangrove fruit flour variation

In general, wet noodles are made from tapioca flour, but the weakness of noodles made from tapioca flour is the lack of nutrients, high carbohydrate content, low protein content, low vitamin content and high gluten content. Making wet noodles with the fortification of mangrove fruits flour and carrageenan is expected to produce wet noodles with physical, chemical, and nutritional characteristics. The method used in this study was an experiment with a factorial randomized block design (RBD). The test was carried out with three replications (triple) with two test parameters, the concentration of carrageenan flour (8%, 12%, 15%) and three mangrove fruit species, namely, Avicennia marina, Bruguierra gymnorrhiza, and Sonneratia caseolaris. Based on the results, the addition of various concentrations of carrageenan flour in wet noodles and using different types of mangrove fruit flour gave significantly different effects (P<0.05) on several test parameters, namely proximate test, crude fibre content, antioxidant activity, water absorption, cooking time, power dropping of noodles, cooking loss, and sensory testing. The addition of carrageenan flour affected the physical and sensory properties of mangrove flour noodles. In addition, different types of mangrove fruit flour affect the increasing nutritional characteristics and antioxidant activity of wet noodles.

Design of a supervisory control system for autonomous operation of advanced reactors

Advanced reactors to be deployed in the coming decades will face deregulated energy markets, and may adopt flexible operation to boost profitability. To aid in the transition from baseload to flexible operation paradigm, autonomous operation is sought. This work focuses on the control aspect of autonomous operation. Specifically, a hierarchical control system is designed to support constraint enforcement during routine operational transients. Within the system, data-driven modeling, physics-based state observation, and classical control algorithms are integrated to provide an adaptable and robust solution. A 320MW Fluoride-cooled High-temperature Pebble-bed Reactor is the design basis for demonstrating the proposed control system.The hierarchical control system consists of a supervisory layer and low-level layer. The supervisory layer receives requests to change the system’s operating conditions (e.g., the current reactor power to meet a load-follow), and accepts or rejects them based on constraints that have been assigned. Constraints are issued to keep the plant within an optimal operating region. The low-level layer interfaces with the actuators of the system to fulfill requested changes, while maintaining tracking and regulation duties. To accept requests at the supervisory layer, the Reference Governor algorithm was adopted. To model the dynamics of the reactor, a system identification algorithm, Dynamic Mode Decomposition, was utilized. To estimate the evolution of process variables that cannot be directly measured (e.g., the propagation of delayed neutron precursors), the Unscented Kalman Filter, incorporating a nonlinear model of nuclear dynamics, was adopted. The composition of these algorithms led to a numerical demonstration of constraint enforcement during a 40% power drop transient (at a rate of 5%/min). Uncontrolled secondary-side temperatures were successfully constrained. Adaptability of the proposed system was demonstrated by modifying the constraint values, and enforcing them during the transient. Robustness was also demonstrated by enforcing constraints under noisy environments.

Computer Aided Intelligent Control of Inlet Air Cooling System in Combined Cycle Power Plant

In hot climate, the overall efficiency of combined cycle power plant (CCPP) decreases dramatically owing to the rise of environment temperature, which decreases the mass air flow to the compressor. Therefore, the gross power and thermal efficiency drop. Worldwide practice uncovers that gas turbines generate up to 20% less power in summer than in winter. A brief introduction of the CCPP and analysis of influence of ambient temperature are provided in this work. Furthermore, this essay gives a outline of the combined cycle based on several inlet air cooling technologies and why they are necessary. Since 1987, more and more inlet air cooling systems have been devised, each of which has its own advantages and limitations. They are mainly divided into 2 classes. Low cost and ease of operation are the main advantages of evaporation systems. However, they are strictly restricted by the wet-bulb temperature. In terms of the mechanical systems, which are not limited to it, command high initial and operating cost. The absorption chiller utilizes the waste heat of exhaust gases, which means they have great potential. In the end, economic criteria and problems to be solved are mentioned.

IMPROVMENT OF ENVIRONMENTAL PERFORMANCE TWO-STROKE DIESEL DURING OPERATION

The development of world shipping is taking place in the context of ever-increasing requirements to reduce the concentrations of toxic components of gaseous combustion products of hydrocarbon fuels. Concentration limits for these substances are regulated in accordance with Appendix VI of the MARPOL 73/78 Convention. Among the controlled components of diesel exhaust gases, nitrogen oxides are the most dangerous for humans and environment. However, a decrease in the content of nitrogen oxides is inevitably associated with limitations on the maximum cycle temperature, that is, thermal efficiency, and hence with a deterioration in the fuel efficiency of the engine. At the moment, in order to reduce emissions of nitrogen oxides by large transport diesel engines, the most widely used is the recirculation of exhaust gases into the air receiver. A significant disadvantage of using this scheme is the need for cooling the exhaust gases and their additional purification, which leads to an increase in the weight and size characteristics of the system and to its rise in price. Therefore, to reduce its cost, it seems logical to combine exhaust gas recirculation with other ways to reduce nitrogen oxide emissions. For engines in operation, one of these methods is to change the angle of fuel injection. It can be assumed that the later the fuel is injected into the cylinder, the lower the temperature of the air charge will be and, accordingly, the lower the maximum combustion temperature, and hence the amount of nitrogen oxides. The calculation of nitrogen oxide emissions was simulated for the main engine MAN-B&W 7S50MC-C installed on the vessel "LILA SHANGHAI". Initially, the model created using the AVL-BOOST package was verified based on the available indexing results. After verification, the calculation of emissions of nitrogen oxides NOx was made with a variation in the angle of the start of fuel combustion at the nominal mode. The composition of the gases in the receiver was taken unchanged. As the fuel combustion start angle shifted further from the TDC, deterioration in fuel efficiency and a drop in cylinder power were observed, while reducing the mass of emitted nitrogen oxides NOx. However, it can be said that the environmental friendliness of an engine improves much faster than its fuel and power characteristics deteriorate. The above calculations show that for engines already in operation, changing the fuel injection angle makes it possible to reduce nitrogen oxide emissions. Therefore, this approach can be combined without much difficulty with other methods, thus reducing the cost of environmental improvement of the engine.

Performance enhancement for exhaust thermoelectric power generation system by using porous pin fins based on a fully automatic optimization method

An intelligent optimization method combining Non-dominated Sorting Genetic Algorithm-II (NSGA-II) algorithm and Technique for Order Preference by Similarity to an Ideal Solution (TOPSIS) decision is implemented to design the optimal arrangement of porous pin fins in the flow channel of the exhaust thermoelectric power generation (ETEG) system. This method realizes the optimal arrangement of the porous pin fins while considering the two contradictory performance indicators at the optimization level: system output power (P) and pressure drop (Pd). In this work, the design of porous and solid pin fins is first compared. Secondly, four typical pin fins arrangement models are established with preliminary analysis. Finally, the NSGA-II-TOPSIS intelligent optimization method is implemented, which takes P and Pd as objective function, the position, number and relative distance of the porous pin fins as optimization variables simultaneously. Through iterative optimization, the optimal arrangement scheme achieves a proper balance between P and Pd. The main conclusions include: The design of the porous pin fins can increase 22.89% for P of the ETEG system while reduces 82.98% for Pd. The distribution of dense downstream of porous pin fins can best improve the ETEG system performance. After optimization, higher P and lower Pd of the ETEG system are obtained with fewer pin fins. A new index is proposed to evaluate optimal solutions, the optimal design with 2 porous pin fins reaches the highest value: 5.86 W Pa−1, which means that each pin fin is fully used.

Frequency regulation in adaptive virtual inertia and power reserve control with high PV penetration by probabilistic forecasting

The large-scale deployment of sustainable energy sources has become a mandatory goal to reduce pollution from electricity production. As photovoltaic (PV) plants replace conventional synchronous generators (SGs), their significant inherent rotational inertia characteristics are reduced. The high penetration of PV results in reduced system inertia, leading to system frequency instability. Virtual inertial control (VIC) technology has attracted increasing interest because of its ability to mimic inertia. Adoption of the energy storage system (ESS) is hindered by the high cost, although it can be used to provide virtual inertia. The determined forecast gives PVs the ability to reserve power before shading and compensate the power when a system power drop occurs, which can increase system inertia. Nevertheless, it has forecast errors and energy waste in a stable state. To improve the stability of the microgrid and improve the ESS efficiency, this study proposes an adaptive forecasting-based (AFB) VIC method using probabilistic forecasts. The adaptive power reserve and virtual inertia control are proposed to reduce energy waste and increase system inertia. The simulation results reveal that the proposed method has adaptive system inertia to reduce the reserved power, required ESS power capacity, and battery aging.

Modeling of the impact of neon seeding on the detachment in EAST by SOLPS-ITER

In the EAST radiative divertor experiments, stable detachment and divertor protection have been achieved with mixed impurity gas seeding. Experiments indicate that neon (Ne) is an appropriate external impurity for plasma detachment in EAST. In this work, the physical mechanism of plasma detachment with Ne seeding in EAST is studied by using the SOLPS-ITER code package. The electron temperature Tet on the upper outer divertor target decreases to below 10 eV with Ne seeding, which is mainly due to the power loss and upstream power drop caused by the impurity radiation. For Tet < 10 eV, the significant drop of the poloidal saturation ion current js,p occurs around the upper outer strike point. The simulation results show that the js,p drop is mainly driven by the rise of the momentum loss and the upstream pressure loss. The increase in the momentum loss is mainly caused by the plasma–neutral interactions in the region from the X-point to the upper outer divertor target. The upstream pressure loss around the X-point is related to the decrease in the upstream electron temperature Teu, which originates from the increased radiation loss with Ne seeding.

Integrating PZT layer with tuned mass damper for simultaneous vibration suppression and energy harvesting considering exciter dynamics: An analytical and experimental study

This paper analytically and experimentally investigates the potential of a tuned mass damper (TMD) with an integrated piezoelectric layer for simultaneous energy harvesting and vibration suppression. The system investigated is composed of a main beam that is excited by a shaker. A TMD comprising a unimorph piezoelectric beam is attached to the main beam. The shaker force drops at the system resonance frequencies means that a constant force sine sweep is difficult in practice, and does not allow model validation and empirical assessment of the TMD. Also, the force drop off phenomenon and an accurate validated shaker model are vital for the modelling, analysis and validation of nonlinear dynamic systems. This paper validates and analyses a linear model, in preparation for future studies of a nonlinear vibration absorber and energy harvester. Therefore, the force drop off phenomenon is examined comprehensively, and a constant shaker input voltage sweep is proposed instead of a constant force sweep. The continuous electromechanical equations governing the coupled system of the main beam-TMD-shaker are developed. The proposed model is then utilized to examine the shaker force drop off, TMD efficiency, and shaker electrical characteristics. The results show that the constant voltage sweep works well to investigate the performance of the TMD and capture the shaker force drop off phenomenon. The TMD suppresses the host structure vibration and harvests energy efficiently, and is demonstrated by extensive experimental investigations. The model is validated by the experiments, including the force drop off. The system parameters have significant effects on the dynamical response of the coupled system and the energy harvested; the effects on the harvested power, reduced vibration, applied force, and force drop off frequencies are demonstrated. Overall, the TMD is shown to be efficient and applicable in reducing vibration and harvesting energy.

The Impact of Soiling on PV Module Performance in Saudi Arabia

Solar photovoltaic (PV) deployment is rapidly expanding around the world. However, the soiling factor has an impact on its performance. Saudi Arabia has high solar irradiation and plans to diversify its energy mix for electricity generation by deploying more solar PV across the country. However, it is located in an arid and desert environment, making it a challenging project due to dust accumulation on solar modules. The soiling and PV performance in Saudi Arabia are examined in this paper. Furthermore, it highlights several mitigation techniques that can be used to maintain PV performance through preventive and restorative measures. Furthermore, this study looks into the size and characterization of dust in Saudi Arabia, as well as the entire life cycle of dust accumulation on PV modules. In this review study, the performance of solar PV systems is evaluated under soiling in different regions of Saudi Arabia. Depending on the local environment and other factors, the PV performance has been reduced by somewhere between 2% and 50%. A single sandstorm reduced the module power output by 20%. As revealed in Dhahran, the PV module was exposed to an outdoor environment and not cleaned for 6 months resulting in a power drop of more than 50%. It is strongly advised to clean PV panels once a month or fewer to maintain a high-performance system. However, in the event of a dust storm, it is advised to clean the system immediately to avoid a major decline in PV performance. The bi-facial PV solar panels technology associated with solar trackers and utilizing robotic cleaning systems have maximized the received solar irradiation and minimized the soiling loss efficiently. The most common elements found in dust particles are primarily derived from the natural desert. It has been noted that the composition and sizes of dust particles depend heavily on the location of the PV module. It is concluded that dust accumulation and cleaning costs are not a significant barrier to large-scale, cost-effective solar PV deployments in Saudi Arabia, particularly in the central region, which is considered a high-suitable region for utility-size PV plants due to many factors. The results of this study are essential for enlightening the PV engineering community, investors, and the research community about how soiling may affect regions with significant solar potential, such as Saudi Arabia, and what potential soiling mitigation strategies may be considered to maintain high-performance solar PV projects.

A novel approach to utilize Al2O3 and polyolefin encapsulant as an optical and electrical materials to mitigate potential-induced of PV modules

The combination of increasing photovoltaic (PV) installation operating voltages of over 1000 V and the discovery of modern PV technologies requires a thorough examination of the sensitivity to potential-induced degradation (PID). An additional dielectric aluminum oxide (Al2O3) layer was coated on a p-type crystalline silicon solar cell to mitigate the effect of PID by reducing the shunting path. We also investigated the effect of PID in the modules fabricated using the conventionally used ethylene-vinyl acetate (EVA) encapsulant and a newly developed next generation polyolefin elastomer (POE) encapsulant. The test was performed in a closed chamber by applying 1000 V between the electrodes and the Al frame and maintaining the conditions of a temperature 85 °C and a relative humidity of 85% for 96 h. Our results demonstrate that the design of the module structure using a POE encapsulant and a solar cell covered with an Al2O3 dielectric layer exhibited a power drop of only 1.37%, while the power drop observed with the conventionally used structure using EVA and without the Al2O3 dielectric layer on the cell was 7.61%. Therefore, the new design can successfully overcome the loss induced by PID in a PV system.

A New Strategy for PI Tuning in Photovoltaic Irrigation Systems Based on Simulation of System Voltage Fluctuations Due to Passing Clouds

One of the greatest challenges in stand-alone photovoltaic irrigation systems (PVIS) without batteries is the tuning of PID controllers and the evaluation of their performance once the system is tuned. Tuning method must be applied in clear days (constant irradiance) while performance must be evaluated in the most unfavourable circumstances, which occur when the passage of a cloud causes a sudden drop in available power. In short, tuning and testing must be done under different weather conditions. To solve this problem, a tuning method that is complemented by a method to simulate voltage fluctuations due to cloud passage has been developed. This allows tuning and evaluation of the system’s performance in the same session. Furthermore, the new PI tuning method achieves a better adjustment of the parameters and solves the instability problems that arise when applying traditional closed-loop tuning methods. Both methods use the feedforward input that most variable frequency drivers have. A signal generator is used to carry out the simulation of the clouds. This input is also used to introduce a triangular signal used for the tuning of the PI controller. The results show that the performance of the system, characterized by the voltage of the PV generator, with simulated clouds is similar to the response with real clouds. With regard to the tuning, the new method achieves better performance than previous methods. These methods can be applied on clear days, under conditions of constant irradiance, which greatly simplifies its implementation and greatly reduces the time required for commissioning the system.

The Influence of UV Light Exposure on the Reliability of Various Front Materials for Lightweight PV Module

The need for innovative design and materials is increasing for various types of photovoltaic (PV) installations in building integrated PV, agricultural, and floating systems. It is crucial to reduce the weight of the PV module to maximize its use in such applications. For this purpose, the front surface must be made of a polymer-based material instead of tempered glass. This study focuses on the analysis of the optical and ultraviolet (UV) reliability properties of various lightweight polymer front sheets. The results show that the transmittance and UV properties of the front material are good. Moreover, a PV module with a polymer front sheet rather than glass was constructed, and a characteristic investigation as well as UV reliability test were performed. The transmittance of the polycarbonate (PC) front sheet decreased by only <3% and the module fabricated with PC exhibited only an approximately 6% power drop after the UV reliability test; hence, the PC is suitable for use in the PV module industry.

Supply less sensitive ring voltage-controlled oscillator for microwave L-band frequencies

PurposeThe primary aim of this paper is to present a novel design approach for a ring voltage-controlled oscillator (VCO) suitable for L-band applications, whose oscillation frequency is less sensitive to power supply variations. In a few decades, with the advancement of modern wireless communication equipment, there has been an increasing demand for low-power and robust communication systems for longer battery life. A sudden drop in power significantly affects the performance of the VCO. Supply insensitive circuit design is the backbone of uninterrupted VCO performance. Because of their important roles in a variety of applications, VCOs and phase locked loops (PLLs) have been the subject of significant research for decades. For a few decades, the VCO has been one of the major components used to provide a local frequency signal to the PLL.Design/methodology/approachFirst, this paper chose to present recent developments on implemented techniques of ring VCO design for various applications. A complementary metal oxide semiconductor (CMOS)-based supply compensation technique is presented, which aims to reduce the change in oscillation frequency with the supply. The proposed circuit is designed and simulated on Cadence Virtuoso in 0.18 µm CMOS process under 1.8 V power supply. Active differential configuration with a cross-coupled NMOS structure is designed, which eliminates losses and negates supply noise. The proposed VCO is designed for excellent performance in many areas, including the L-band microwave frequency range, supply sensitivity, occupied area, power consumption and phase noise.FindingsThis work provides the complete design aspect of a novel ring VCO design for the L-band frequency range, low phase noise, low occupied area and low power applications. The maximum value of the supply sensitivity for the proposed ring VCO is 1.31, which is achieved by changing the VDD by ±0.5%. A tuning frequency range of 1.47–1.81 GHz is achieved, which falls within the L-band frequency range. This frequency range is achieved by varying the control voltage from 0.0 to 0.8 V, which shows that the proposed ring VCO is also suitable for low voltage regions. The total power consumed by the proposed ring VCO is 14.70 mW, a remarkably low value using this large transistor count. The achievable value of phase noise is −88.76 dBc/Hz @ 1 MHz offset frequency, which is a relatively small value. The performance of the proposed ring VCO is also evaluated by the figure of merit, achieving −163.13 dBc/Hz, which assures the specificity of the proposed design. The process and temperature variation simulations also validate the proposed design. The proposed oscillator occupied an extremely small area of only 0.00019 mm2 compared to contemporary designs.Originality/valueThe proposed CMOS-based supply compensation method is a unique design with the size and other parameters of the components used. All the data and results obtained show its originality in comparison with other designs. The obtained results are preserved to the fullest extent.

Analysis and improvement of output power drop of dynamic wireless power transfer systems with transmitting coil switching for inspection robots

Analysis and improvement of output power drop of dynamic wireless power transfer systems with transmitting coil switching for inspection robots

Suppression of scalar power on large scales and associated bispectra

A sharp cutoff in the primordial scalar power spectrum on large scales has been known to improve the fit to the cosmic microwave background (CMB) data when compared to the more standard, nearly scale invariant power spectra that arise in slow roll inflation. Over the last couple of years, there has been resurgent interest in arriving at such power spectra in models with kinetically dominated initial conditions for the background scalar field which leads to inflation of specific duration. In an earlier work, we had numerically investigated the characteristics of the scalar bispectrum generated in such models. In this work, we compare the scenario with two other competing scenarios (viz., punctuated inflation and a model proposed by Starobinsky) which also suppress the scalar power in a roughly similar fashion on large scales. We further consider two other scenarios involving inflation of a finite duration, one wherein the scalar field begins on the inflationary attractor and another wherein the field starts with a smaller velocity and evolves toward the attractor. These scenarios too exhibit a sharp drop in power on large scales if the initial conditions on the perturbations for a range of modes are imposed on super-Hubble scales as in the kinetically dominated model. We compare the performance of all the models against the Planck CMB data at the level of scalar power spectra. The model wherein the background field always remains on the inflationary attractor is interesting for the reason that it permits analytical calculations of the scalar power and bi-spectra. We also compare the amplitudes and shapes of the scalar non-Gaussianity parameter ${f}_{\mathrm{NL}}$ in all these cases which lead to scalar power spectra of similar form. Interestingly, we find that, in the models wherein the initial conditions on the perturbations are imposed on super-Hubble scales, the consistency relation governing the scalar bispectrum is violated for the large-scale modes, whereas the relation is satisfied for all the modes in the other scenarios. These differences in the behavior of the scalar bispectra can conceivably help us observationally discriminate between the various models which lead to scalar power spectra of roughly similar shape.

Comparison of Phase-Shifting Transformers Properties

This article presents different phase shifting transformers (PSTs) types and their influence on the transmitted active power and energy parameters. Typical PSTs, both symmetrical (SPST) and asymmetrical (APST), are compared to the asymmetrical controllable PST (ACPST). The ACPST allows for regulating both quadrature and longitudinal voltage, which makes this type interesting in practical applications and power flow optimizations. The collected data enable a direct comparison of these PSTs’ properties. APST allows high power transfer, but the voltage increase in some cases cannot be acceptable. SPST type in taken tests has the best properties concerning the transferred power, output voltage, and internal voltage drop. ACPST, in its primary mode, can be efficiently used as a substitute for the SPST. However, in some range of injected quadrature voltages, it can achieve even better properties than the SPST. The laboratory and simulation tests allow the development of the ACPST regulation to achieve the best properties among other PSTs, with the possibility to operate, e.g., on the constant ACPST output voltage, in quasi-symmetrical mode and any other, which may be needed in power systems.