Advanced controller design based on gain and phase margin for microgrid containing PV/WTG/Fuel cell/Electrolyzer/BESS

Nowadays, with the increase in the amount of power generation related to renewable energy resources, the need for energy storage and management is raised. In this regard, the hydrogen energy plays a critical role in the development of renewable technologies. In view of the above, advanced controller design is presented in this paper to effectively perform load frequency control of islanded fuel cell microgrid based on the wind turbine, photovoltaic, fuel cell, electrolyzer, battery energy storage systems, and residential and commercial loads. The controller design is based on the determination of the controller parameters that the fuel cell microgrid system will provide the desired dynamic properties. In the proposed controller design, virtual gain and phase margin testers are added to provide the desired dynamic properties. The controller's stable parameter plane is determined with the help of the stability boundary locus method, taking into account time delay, gain, and phase margin. First, the accuracy of the stable parameter plane determined for the proposed controller design is demonstrated by means of time domain and eigenvalue analyzes. Finally, in order to show the performance of the advanced controller design and the success of the fuel cell as a backup generator, analysis studies have been carried out using actual data of solar and wind, and appropriate changes of load in studied microgrid.     

Full and reduced-order H∞ filtering of Takagi–Sugeno fuzzy time-varying delay systems: Input–output approach

This article addresses the issue of delay-dependent H_∞ filtering design for TakagiŮSugeno fuzzy time-varying delay systems using the input–output approach. A three-term approximation model has been used to transform the original system into two interconnected subsystems. Since the nonquadratic Lyapunov–Krasovskii functional requires to deal with the membership function's (MF) time derivative, upper-bound inequalities have been added to the obtained conditions. Based on the scaled small gain theorem, nonquadratic Lyapunov–Krasovskii functional approach and considering the bounds of the MF time-derivative, the H_∞ full- and reduced-order filters are designed and then formulated in terms of linear matrix inequalities. Finally, illustrative examples are presented to demonstrate the validity of the proposed methods.     

0Cr17Ni4Cu4Nb传感器断裂原因分析

某力学传感器在出厂检验流程中发生断裂失效,为了确定失效原因,防止此类失效事件再次发生,实验对该传感器的力学性能、金相组织和断口形貌进行了分析,确定了断裂原因。结果表明,传感器的失效模式为氢致延迟开裂,材料中氢含量偏高和开裂位置机加工质量较差是导致传感器发生氢致开裂的主要原因。结合失效原因,提出了改进措施。     

基于时间延迟的多类型维修与经济生产批量联合优化研究

针对目前未能较好的综合考虑多维修类型与经济生产批量联合优化的问题，首先考虑多类型维修关系，基于时间延迟理论求出故障和缺陷次数的表达式；其次，在此基础上，综合考虑生产费用和维修费用的基础上，构建了多类型维修和经济生产批量联合优化模型，以单位时间内总费用最小为优化目标，获得最优检查间隔期和经济生产批量；最后，通过算例分析验证了模型的有效性，说明了第一类缺陷检查次数的多少对费用和经济生产批量影响不大。     

Improved CCM for variable causality detection in complex systems

Convergent cross-mapping (CCM), has been largely implemented for variable causality detection in complex systems like chemical process. However, this method is susceptible to problems regarding parameter selection and threshold determination. The synchronization phenomenon and the Moran effect, which are two interference terms in causality detection, must also be addressed. Therefore, an improved CCM is proposed to overcome these limitations in this paper. In the improved CCM, the optimal embedding dimension is selected based on the pseudo-nearest-neighbor theory. Also, Monte Carlo simulation is adopted to evaluate the convergence threshold. Next, by using the defined time delay detection function, the synchronization phenomenon and the Moran effect are identified to reduce the interference terms and further improve the accuracy. Finally, the improved CCM method is applied in a numerical example and a hydrocracking process to demonstrate its feasibility and superior performance than other methods.     

Impact of oxygenated cottonseed biodiesel on combustion,performance and emission parameters in a direct injection CI engine

In the present study, biodiesel production from the crude cotton-seed oil (CSO) and its feasibility to be used as fuel in compression ignition engine was analysed. Single-stage transesterification at molar ratio of 8:1 on crude CSO yielded 94% of cottonseed biodiesel (CBD). Gas chromatogram/mass spectrometry analysis revealed the presence of 19.5% unsaturated and 80.5% saturated esters in cotton seed biodiesel. Taguchi approach identified the stable fuel blend with oxygenate concentration. Increased oxygen concentration up to 20% were also analysed to understand the variation. Higher peak in-cylinder pressure was observed in D80CBD20 fuel blend. Diesel–biodiesel blend with oxygenate significantly affected the ignition delay and also resulted in varied exhaust gas temperature. D80CBD20nB10 showed an increase in brake thermal efficiency, whereas D80CBD20 exhibited higher brake specific energy consumption at full load. Carbon monoxide, hydrocarbon and smoke emission was found to be high in diesel with higher oxides of nitrogen in D80CBD20nB10. This experimental investigation finally revealed that, D80CBD20nB10 improved the combustion and performance characteristics with minimal emissions.

Abbreviations ASTM: American Society for Testing and Materials; BP: brake power; BSEC: brake specific energy consumption; BTE: brake thermal efficiency; CBD: cottonseed biodiesel; CI: compression ignition; CO: carbon monoxide; CO₂: carbon dioxide; CSO: cottonseed oil; DEE: diethyl ether; DOE: design of experiments; EGT: exhaust gas temperature; FTIR: Fourier transform infrared spectrometry; GC/MS: gas chromatogram/mass spectrometry; HC: hydrocarbon; HRR: heat release rate; HSDI: high speed direct injection; IDI: indirect injection; KOH: potassium hydroxide; MFB: mass fraction burned; NaOH: sodium hydroxide; NMR: nuclear magnetic resonance; N₂O: nitrous oxide; NO: nitric oxide; NO₂: nitrogen dioxide; NO _x : oxides of nitrogen; ROHR: rate of heat release; ROPR: rate of pressure rise; SOC: start of combustion; aTDC: after top dead centre; bTDC: before top dead centre     

Improved Input and State Estimation for Linear Stochastic Systems with Direct Feedthrough

This paper is concerned with the problem of joint input and state estimation for linear stochastic systems with direct feedthrough. Based on the fact that each unknown input between any two time steps is always bounded, a novel improved algorithm is proposed. Compared with existing results, this algorithm can effectively enhance estimation accuracy. Moreover, the stability of the algorithm is also discussed. Finally, an illustrative example is given to demonstrate the effectiveness of the proposed approach.     

Switching controller design for linear time invariant plant with a single I/O delay

ABSTRACT

To deal with the problem of conflicting requirements that cannot be satisfied by only a single LTI controller, this paper focuses on the design of a switching controller, which includes several stabilising linear time-invariant (LTI) controllers designed independently with different control performance criteria, for a specific LTI plant with a single I/O delay. The switching controller design procedure is divided into three steps. First, using simple loop shifting arguments, the design problem is reducible to an equivalent delay-free one. Second, traditional LTI controller synthesis methods could be considered independently for the delay-free plant. Third, based on a quadratically stable state space realisation method, a Youla parameter including a switching strategy with these controllers is designed to guarantee different requirements. Finally, a numerical example is provided to demonstrate the validity and efficiency of the approach.