Comparative analysis of the growth and survival of protozoa stages of Penaeus semisulcatus fed with four phytoplankton species

Four genera of phytoplankton including Tetraselmis, Chaetoceros, Sketetonema and Cholorella were used as food for protozoa stages of Penaeus semisulcatus in 10 treatmeants each with three replications of singular and double diets. In singular diet consisted of 40,000 cells/ ml of Skeletonenia, we recorded a survival rate 82°, growth rate 3.55 mm and period of development stage (Z1-MI) 92h which were higher than other treatments. In double diet comprised of Chaeloceros and Tetraselmis, the survival rate in Z 1 stake was 97/0, higher than other treatments while in Z2 and Z3 stages, the highest survival rate was 95%, achieved by a double diet consisted of Skeletonema and Chaetoceros. In the latter diet, the uowth rate and period of development for Z I -Ml stakes were 4.58mm and 72h respectively. According to the results, we conclude that the survival and growth rates in simuilar diets are higher than double diets of the phytoptankton species

Coordination of heat pumps, electric vehicles and AGC for efficient LFC in a smart hybrid power system via SCA-based optimized FOPID controllers

© 2018 by the authors. Licensee MDPI, Basel, Switzerland. Due to the high price of fossil fuels, the increased carbon footprint in conventional generation units and the intermittent functionality of renewable units, alternative sources must contribute to the load frequency control (LFC) of the power system. To tackle the challenge, dealing with controllable loads, the ongoing study aims at efficient LFC in smart hybrid power systems. To achieve this goal, heat pumps (HPs) and electric vehicles (EVs) are selected as the most effective controllable loads to contribute to the LFC issue. In this regard, the EVs can be controlled in a bidirectional manner as known charging and discharging states under a smart structure. In addition, regarding the HPs, the power consumption is controllable. As the main task, this paper proposes a fractional order proportional integral differential (FOPID) controller for coordinated control of power consumption in HPs, the discharging state in EVs and automatic generation control (AGC). The parameters of the FOPID controllers are optimized simultaneously by the sine cosine algorithm (SCA), which is a new method for optimization problems. In the sequel, four scenarios, including step and random load changes, aggregated intermittent generated power from wind turbines, a random load change scenario and a sensitivity analysis scenario, are selected to demonstrate the efficiency of the proposed SCA-based FOPID controllers in a hybrid two-area power system

Improving fault ride-through of three phase voltage source inverter during symmetrical fault using DC link fault current limiter

The majority of distributed generation (DG) units utilize three phase voltage source inverter (VSI) to exchange electric power with the utility grid. The VSI employs semiconductor devices (SDs) with limited current withstand capabilities which are very vulnerable during grid faults. However, to ensure a secure and reliable operation of power systems at high penetration level of the DGs, most of the new grid codes worldwide require that the VSIs must have fault ride-through (FRT) capability. This paper presents a DC link fault current limiter (DLFCL) based VSI FRT scheme to improve its FRT capability. In the proposed scheme, the DLFCL is connected in series with the DC side of the VSI to limit the output current during symmetrical grid fault. The DLFCL does not have considerable effect on the VSI performance during the normal operation, whereas it limits the output current in all phases to the safe area operation of the SDs of the inverter. The effectiveness of the proposed scheme is validated through the simulation studies in PSCAD/EMTDC software

How Historians Play God

This essay recounts the career of Jacques-Pierre Brissot, the leader of the Girondists during the French Revolution, in a manner designed to pose questions about the nature of historical research in general. How, in piecing together information taken from scraps of paper, do historians come to an understanding of other lives? Put in the abstract, the problem belongs to epistemology or ethics. Confronted in practice, it is more like the puzzles uncovered by archaeologists. The historian digs out a shard of evidence from the archives and asks: was Brissot, the ultimate idealist, a spy for the police? By stepping in and out of layers of time, the historian is actually playing a deeper game, one that he or she may be reluctant to admit.Histor

Optimum resistive type fault current limiter: An efficient solution to achieve maximum fault ride-through capability of fixed-speed wind turbines during symmetrical and asymmetrical grid faults

This paper proposes an optimum resistive type fault current limiter (OR-FCL) as an efficient solution to achieve maximum fault ride-through (FRT) capability of fixed-speed wind turbines (FSWT) during various grid faults. In this paper, a dedicated control circuit is designed for the OR-FCL that enables it to insert an optimum value of resistance in the FSWT\u27s fault current\u27s path for improving transient behavior of the FSWT. The optimum resistance value depends on fault location and prefault active power. The control circuit of the proposed OR-FCL is capable of calculating the optimum resistance value for all the prefault conditions. By using the proposed control circuit, the FSWT can achieve its maximum FRT capability during symmetrical and asymmetrical faults, even at zero grid voltage. Analysis is provided in detail to highlight the process of calculating the optimum resistance of the OR-FCL. Moreover, the effect of the resistance value of the OR-FCL on the FRT behavior of FSWT is investigated. To show the efficiency of the proposed OR-FCL, its performance during various operation conditions of the FSWT is studied. It can be proved that each operation condition needs its own optimum resistance value, which can be obtained by using the proposed control circuit during the fault to achieve the maximum FRT capability of the FSWT. Comprehensive sets of simulations are carried out in PSCAD/EMTDC software and the results prove the effectiveness of the proposed approach