Layered power scheduling optimization of PV hydrogen production system considering performance attenuation of PEMEL

To analyze the additional cost caused by the performance attenuation of a proton exchange membrane electrolyzer(PEMEL)under the fluctuating input of renewable energy,this study proposes an optimization method for power scheduling in hydrogen production systems under the scenario of photovoltaic(PV)electrolysis of water.First,voltage and performance attenuation models of the PEMEL are proposed,and the degradation cost of the electrolyzer under a fluctuating input is considered.Then,the calculation of the investment and operating costs of the hydrogen production system for a typical day is based on the life cycle cost.Finally,a layered power scheduling optimization method is proposed to reasonably distribute the power of the electrolyzer and energy storage system in a hydrogen production system.In the up-layer optimization,the PV power absorbed by the hydrogen production system was optimized using MALTAB+Gurobi.In low-layer optimization,the power allocation between the PEMEL and battery energy storage system(BESS)is optimized using a non-dominated sorting genetic algorithm(NSGA-Ⅱ)combined with the firefly algorithm(FA).A better optimization result,characterized by lower degradation and total costs,was obtained using the method proposed in this study.The improved algorithm can search for a better population and obtain optimization results in fewer iterations.As a calculation example,data from a PV power station in northwest China were used for optimization,and the effectiveness and rationality of the proposed optimization method were verified.

Ling'ao Nuclear Power Plant is progressing as scheduled

Construction of Ling’ao Nuclear Power Plant in Guangdong Province, the country’s second-largest nuclear power project between 1996-2000, chalked up notable progress this year. On July, 15, all foreign suppliers in the project were given official notice that both sides should start to implement the contracts. "The move marked a significant step forward in the project’s construction," said Zeng Wenxing, General Manager of Ling’ ao Nuclear Power Co Ltd, set up in

Integrated Frequency-constrained Scheduling Considering Coordination of Frequency Regulation Capabilities from Multi-source Converters

As the proportion of renewable energy(RE)increases,the inertia and the primary frequency regulation(FR)capability of the power system decrease.Thus,ensuring frequency security in the scheduling model has become a new technical requirement in power systems with a high share of RE.Due to a shortage of conventional synchronous generators,the frequency support of multi-source converters has become an indispensable part of the system frequency resources,especially variable-speed wind turbine generation(WTG)and battery energy storage(BES).Quantitative expression of the FR capability of multi-source converters is necessary to construct frequency-constrained scheduling model.However,the frequency support performance of these converter-interfaced devices is related to their working states,operation modes,and parameters,and the complex coupling of these factors has not been fully exploited in existing models.In this study,we propose an integrated frequency-constrained scheduling model considering the coordination of FR capabilities from multi-source converters.Switchable FR control strategies and variable FR parameters for WTG with or without reserved power are modeled,and multi-target allocation of BES capacity between tracking dispatch instruction and emergency FR is analyzed.Then,the variable FR capabilities of WTG and BES are embedded into the integrated frequency-constrained scheduling model.The nonlinear constraints for frequency security are precisely linearized through an improved iteration-based strategy.The effectiveness of the proposed model is verified in a modified IEEE 24-bus standard system.The results suggest that the coordinated participation of BES and WTG in FR can effectively reduce the cost of the scheduling model while meeting frequency security constraints.

Complete active-reactive power resource scheduling of smart distribution system with high penetration of distributed energy resources

In traditional power systems,besides the conventional power plants that provide the necessary reactive power in transmission system,the shunt capacitors along with the tap changers of transformers are also employed in distribution networks.In future years,because of the high number of distributed resources integrated into the distribution networks,it will be essential to schedule complete active-reactive power at distribution level.In this research work,an economic framework based on the active-reactive power bids has been developed for complete active-reactive power dispatch scheduling of smart distribution networks.The economical complete active-reactive power scheduling approach suggested in this study motivates distributed energy resources(DERs)to cooperate in both active power markets and the Volt/Var control scheme.To this end,using DER’s reactive power capability,a generic framework of reactive power offers for DERs is extracted.A 22-bus distribution test system is implemented to verify the impressiveness of the suggested active-reactive power scheduling approach.

FastAFLGo:Toward a Directed Greybox Fuzzing

While the size and complexity of software are rapidly increasing,not only is the number of vulnerabilities increasing,but their forms are diversifying.Vulnerability has become an important factor in network attack and defense.Therefore,automatic vulnerability discovery has become critical to ensure software security.Fuzzing is one of the most important methods of vulnerability discovery.It is based on the initial input,i.e.,a seed,to generate mutated test cases as new inputs of a tested program in the next execution loop.By monitoring the path coverage,fuzzing can choose high-value test cases for inclusion in the new seed set and capture crashes used for triggering vulnerabilities.Although there have been remarkable achievements in terms of the number of discovered vulnerabilities,the reduction of time cost is still inadequate.This paper proposes a fast directed greybox fuzzing model,FastAFLGo.A fast convergence formula of temperature is designed,and the energy scheduling scheme can quickly determine the best seed to make the program execute toward the target basic blocks.Experimental results show that FastAFLGo can discover more vulnerabilities than the traditional fuzzing method in the same execution time.

Efective Object Identification and Association by Varying Coverage Through RFID Power Control

This paper presents an effective power scheduling strategy for energy efficient multiple objects identification and association. The proposed method can be utilized in many heterogeneous surveillance systems with visual sensors and RFID （radio-frequency identification） readers where energy efficiency as well as association rate are critical Multiple objects positions and trajectory estimates are used to decide the power level of RFID readers. Several key parameters including the time windows and the distance separations are defined in the method in order to minimize the effects of RFID coverage uncertainty. The power cost model is defined and incorporated into the method to minimize energy consumption and to maximize association performance. The proposed method computes the power cost using the range of the outermost position for possible single association and group associations at every sampling time. An RFID reader is activated with the proper coverage range when the power cost for the current time is lower than the power cost for the next time sample. The simplicity of the power cost model relieves the problematic combinatorial comparisons in multiple object cases. The performance comparison simulation with the minimum and maximum energy consumption shows that the proposed method achieves fast single associations with less energy consumption. Finally, the realistic comparison simulation with the fixed range RFID readers demonstrates that the proposed method outperforms the fixed ranges in terms of single association rate and energy consumption.

Method for designing constant thrust power schedule

In order to make the power level angle(PLA)have the same bijection relationship with the thrust when the environment changes before operational limit exceedance,and ensure the pilot's ability of unrestricted throttle movement as well as the safety of the engine,a method used to design a constant thrust power schedule was proposed.The research was based on a simulink turbofan engine model and the results were organized as look-up tables in different structures with limitations.Simulation was done to confirm the validity and demonstrate the effectiveness of the schedule obtained with the approach.The constant thrust takeoff schedule,constant thrust idle schedule and constant thrust part power schedule with the present constant thrust control(CTC)method were proved to be valid.The results can be applied to this specific engine but the method can be applied to any areoengine and can be even extended to the unmanned plane.

Exploiting write power asymmetry to improve phase change memory system performance

Phase change memory （PCM） is a promising can- didate to replace DRAM as main memory, thanks to its bet- ter scalability and lower static power than DRAM. However, PCM also presents a few drawbacks, such as long write la- tency and high write power. Moreover, the write commands parallelism of PCM is restricted by instantaneous power con- straints, which degrades write bandwidth and overall perfor- mance. The write power of PCM is asymmetric： writing a zero consumes more power than writing a one. In this paper, we propose a new scheduling policy, write power asymme- try scheduling （WPAS）, that exploits the asymmetry of write power. WPAS improves write commands parallelism of PCM memory without violating power constraint. The evaluation results show that WPAS can improve performance by up to 35.5%, and 18.5% on average. The effective read latency can be reduced by up to 33.0%, and 17.1% on average.

Erratum to: An Improved Simple Power Attack against Camellia's Key Schedule

Retraction： LIU Shuanggen, NI Haiying, HU Yupu, LIAO Yunyan. An Improved Simple Power Attack against Camellia＇s Key Schedule. Wuhan University Journal of Natural Sciences, 2008, 13（5）： 591-594. DOI： 10.1007/s 11859-008-0516-3

An Optimal Dispatch Strategy for Distributed Microgrids Using PSO

Grid structures are rapidly evolving in view of contemporary energy policies which ensure the addition of more renewable sources to reduce the carbon footprint.Compared to a centralized approach,low voltage grids(decentralized and distributed)are promising approaches to integrating nondispatchable renewable energy sources(RESs).Installing local micro level power generation sources such as fuel cells,microturbines,and energy storage systems are a recent trend which helps in the intermittent effects of RESs and makes microgrids less dependable on the main grid.Due to the increasing variety of distributed generation sources having diverse characteristics,power dispatch scheduling of distributed microgrids is becoming challenging.A dispatch scheduling solution from an operator’s point of view is presented by the authors.The core objective of this study is to minimize the carbon emissions and the cost of each microgrid.Further,it is observed that sales and purchases from the main grid are reduced.Consequently,transmission losses are also decreased.

Distributed Estimation for Sensor Networks with Channel Estimation Errors

This paper describes the effect of channel estimation error （CEE） on the performance of distributed estimations of an unknown parameter in a wireless sensor network. Both the classical and Bayesian estimators are derived to mitigate the adverse effects caused by the CEE. Power scheduling among sensors and the power ratio between the training and data transmission at each individual node are optimized by directly minimizing the final average mean squared error to compensate for the CEE. A closed-form power scheduling policy is given for a homogeneous environment, which shows that more than 50% of the power should be allocated to sensor observation transmissions. For an inhomogeneous environment, a multilevel waterfilling type solution is developed for the power scheduling among sensors for only the sum power constraint with a ＂cave＂ waterfilling solution for both the sum and individual power constraints. Simulations show that the proposed power scheduling schemes achieve better performance than the equal power scheduling scheme.

ROPAS:Cross-Layer Cognitive Architecture for Mobile UWB Networks

The allocation of bandwidth to unlicensed users, without significantly increasing the interference on the existing licensed users, is a challenge for Ultra Wideband （UWB） networks. Our research work presents a novel Rake Optimization and Power Aware Scheduling （ROPAS） architecture for UWB networks. Since UWB communication is rich in multipath effects, a Rake receiver is used for path diversity. Our idea of developing an optimized Rake receiver in our ROPAS architecture stems from the intention of reducing the computation complexity in terms of the number of multiplications and additions needed for the weight derivation attached to each finger of the Rake receiver. Our proposed work uses the Cognitive Radio （CR） for dynamic channel allocation among the requesting users while limiting the average power transmitted in each sub-band. In our proposed novel ROPAS architecture, dynamic channel allocation is achieved by a CR-based cross-layer design between the PHY and Medium Access Control （MAC） layers. Additionally, the maximum number of parallel transmissions within a frame interval is formulated as an optimization problem. This optimal decision is based on the distance parameter between a transmitter-receiver pair, bit error rate and frequency of request by a particular application. Moreover, the optimization problem improvises a differentiation technique among the requesting applications by incorporating priority levels among user applications. This provides fairness and higher throughput among services with varying power constraint and data rates required for a UWB network.

Improved resource allocation strategy in SU-CoMP network

Coordinated multi-point transmission and reception （CoMP） for single user, named as SU-CoMP, is considered as an efficient approach to mitigate inter-cell interference in orthogonal frequency division multiple access （OFDMA） systems. Two prevalent approaches in SU-CoMP are coordinated scheduling （CS） and joint processing （JP）. Although JP in SU-CoMP has been proved to achieve a great link performance improvement for the cell-edge user, efficient resource allocation （RA） on the system level is quite needed. However, so far limited work has been done considering JP, and most existing schemes achieved the improvement of cell-edge performance at cost of the cell-average performance degradation compared to the single cell RA. In this paper, a two-phase strategy is proposed for SU-CoMP networks. CS and JP are combined to improve both cell-edge and cell-average performance. Compared to the single cell RA, simulation results demonstrate that, the proposed strategy leads to both higher cell-average and cell-edge throughput.