Automatic voltage regulators(AVR)are designed to manipulate a synchronous generator’s voltage level automatically.Proportional integral derivative(PID)controllers are typically used in AVR systems to regulate voltage...Automatic voltage regulators(AVR)are designed to manipulate a synchronous generator’s voltage level automatically.Proportional integral derivative(PID)controllers are typically used in AVR systems to regulate voltage.Although advanced PID tuning methods have been proposed,the actual voltage response differs from the theoretical predictions due to modeling errors and system uncertainties.This requires continuous fine tuning of the PID parameters.However,manual adjustment of these parameters can compromise the stability and robustness of the AVR system.This study focuses on the online self-tuning of PID controllers called indirect design approach-2(IDA-2)in AVR systems while preserving robustness.In particular,we indirectly tune the PID controller by shifting the frequency response.The new PID parameters depend on the frequency-shifting constant and the previously optimized PID parameters.Adjusting the frequency-shifting constant modifies all the PID parameters simultaneously,thereby improving the control performance and robustness.We evaluate the robustness of the proposed online PID tuning method by comparing the gain margins(GMs)and phase margins(PMs)with previously optimized PID parameters during parameter uncertainties.The proposed method is further evaluated in terms of disturbance rejection,measurement noise,and frequency response analysis during parameter uncertainty calculations against existing methods.Simulations show that the proposed method significantly improves the robustness of the controller in the AVR system.In summary,online self-tuning enables automated PID parameter adjustment in an AVR system,while maintaining stability and robustness.展开更多
This paper is concerned with the problem of the full-order observer design for a class of fractional-order Lipschitz nonlinear systems. By introducing a continuous frequency distributed equivalent model and using an i...This paper is concerned with the problem of the full-order observer design for a class of fractional-order Lipschitz nonlinear systems. By introducing a continuous frequency distributed equivalent model and using an indirect Lyapunov approach, the sufficient condition for asymptotic stability of the full-order observer error dynamic system is presented. The stability condition is obtained in terms of LMI, which is less conservative than the existing one. A numerical example demonstrates the validity of this approach.展开更多
In the process of quantifying optimum seismic design parameters, the losses implying the failure of the system must be assessed. Intangibles such as human lives may lie among indirect losses. In this paper, we propose...In the process of quantifying optimum seismic design parameters, the losses implying the failure of the system must be assessed. Intangibles such as human lives may lie among indirect losses. In this paper, we propose a model to calculate the value of the investment that society should be willing to make for saving lives. In order to do this, we analyze both individual and social problems. However, special treatment is given to the individual problem where the value of the life of a human being is inferred by what the person should be willing to pay or willing to accept to reduce the risk of dying. Due to the use of utility curves in the calculation of this kind of intangible, we pay special attention to shape and requirement conditions of these curves. We also pay attention when personal impact and legacies or bequests are considered in utility curves. The results are shown through some applications, especially in the computation of optimum seismic design coefficients at a low seismicity site.展开更多
Reliability-based design (RBD) is being adopted by geotechnical design codes worldwide, and it is therefore necessary that rock engineering practice evolves to embrace RBD. This paper examines the Hoek-Brown (H-B) str...Reliability-based design (RBD) is being adopted by geotechnical design codes worldwide, and it is therefore necessary that rock engineering practice evolves to embrace RBD. This paper examines the Hoek-Brown (H-B) strength criterion within the RBD framework, and presents three distinct analyses using a Bayesian approach. Firstly, a compilation of intact compressive strength test data for six rock types is used to examine uncertainty and variability in the estimated H-B parameters m and σc, and corresponding predicted axial strength. The results suggest that within- and between-rock type variabilities are so large that these parameters need to be determined from rock testing campaigns, rather than reference values being used. The second analysis uses an extensive set of compressive and tensile (both direct and indirect) strength data for a granodiorite, together with a new Bayesian regression model, to develop joint probability distributions of m and σc suitable for use in RBD. This analysis also shows how compressive and indirect tensile strength data may be robustly used to fit an H-B criterion. The third analysis uses the granodiorite data to investigate the important matter of developing characteristic strength criteria. Using definitions from Eurocode 7, a formal Bayesian interpretation of characteristic strength is proposed and used to analyse strength data to generate a characteristic criterion. These criteria are presented in terms of characteristic parameters mk and σck, the values of which are shown to depend on the testing regime used to obtain the strength data. The paper confirms that careful use of appropriate Bayesian statistical analysis allows the H-B criterion to be brought within the framework of RBD. It also reveals that testing guidelines such as the International Society for Rock Mechanics and Rock Engineering (ISRM) suggested methods will require modification in order to support RBD. Importantly, the need to fully understand the implications of uncertainty in nonlinear strength criteria is identified.展开更多
【目的】针对南方污水处理厂运行中普遍存在的低碳氮比(C/N=4.5~6.0)水质特点,探索提升原水碳源利用效率、降低曝气能耗,并实现高效低碳脱氮的调控策略和技术方案。【方法】通过开展5.0 m^(3)/h的中试试验,提出了5段Bardenpho工艺与多...【目的】针对南方污水处理厂运行中普遍存在的低碳氮比(C/N=4.5~6.0)水质特点,探索提升原水碳源利用效率、降低曝气能耗,并实现高效低碳脱氮的调控策略和技术方案。【方法】通过开展5.0 m^(3)/h的中试试验,提出了5段Bardenpho工艺与多级缺氧-好氧(AO)工艺的高效低碳运行优化方案和调控策略,并利用碳排放核算分析,对比了不同生物脱氮工艺的碳排放强度,进而提出了污水强化生物脱氮的优化设计与低碳运行策略。同时,在湖北省某污水处理厂开展了工程应用,以期为未来污水处理厂的生化处理系统减污降碳协同增效提供技术参考。【结果】通过实施多点进水和微氧控制等调控手段,将前置好氧区的溶解氧控制在1.0~1.5 mg/L,后置好氧区控制在2.0~2.5 mg/L,五段Bardenpho工艺和多级AO工艺原水内碳源利用率提高20.95%以上,同时提升了5%~14%的反硝化脱氮效率,并实现了2%~6%的电能节约。经核算,5段Bardenpho工艺和多级AO工艺的总碳排放强度分别为0.229 kg CO_(2)/m^(3)和0.211 kg CO_(2)/m^(3)。【结论】相对于传统厌氧-缺氧-好氧(AAO)工艺,通过对5段Bardenpho工艺和多级AO工艺进行优化调控,成功实现了低碳高效运行,不仅提升了脱氮除磷效果,还同步实现了节能降耗。为显著提升活性污泥工艺的脱氮效率并促进节能减碳,工程设计需前瞻,预留充足设计余量与设施,构建精准灵活的调控框架。通过优化碳源分配、调整混合液回流比、控制污泥浓度及调节溶解氧浓度,确保水质达标,提升效能,实现资源高效利用与碳减排。展开更多
基金the Malaysian Ministry of Higher Education(MOHE)for their support through the Fundamental Research Grant Scheme(FRGS/1/2021/ICT02/UMP/03/3)(UMPSA Reference:RDU 210117)。
文摘Automatic voltage regulators(AVR)are designed to manipulate a synchronous generator’s voltage level automatically.Proportional integral derivative(PID)controllers are typically used in AVR systems to regulate voltage.Although advanced PID tuning methods have been proposed,the actual voltage response differs from the theoretical predictions due to modeling errors and system uncertainties.This requires continuous fine tuning of the PID parameters.However,manual adjustment of these parameters can compromise the stability and robustness of the AVR system.This study focuses on the online self-tuning of PID controllers called indirect design approach-2(IDA-2)in AVR systems while preserving robustness.In particular,we indirectly tune the PID controller by shifting the frequency response.The new PID parameters depend on the frequency-shifting constant and the previously optimized PID parameters.Adjusting the frequency-shifting constant modifies all the PID parameters simultaneously,thereby improving the control performance and robustness.We evaluate the robustness of the proposed online PID tuning method by comparing the gain margins(GMs)and phase margins(PMs)with previously optimized PID parameters during parameter uncertainties.The proposed method is further evaluated in terms of disturbance rejection,measurement noise,and frequency response analysis during parameter uncertainty calculations against existing methods.Simulations show that the proposed method significantly improves the robustness of the controller in the AVR system.In summary,online self-tuning enables automated PID parameter adjustment in an AVR system,while maintaining stability and robustness.
基金supported by National Natural Science Foundation of China(Nos.61104072,61104210 and 61174211)Construct Program of the Key Discipline in Hunan Province
文摘This paper is concerned with the problem of the full-order observer design for a class of fractional-order Lipschitz nonlinear systems. By introducing a continuous frequency distributed equivalent model and using an indirect Lyapunov approach, the sufficient condition for asymptotic stability of the full-order observer error dynamic system is presented. The stability condition is obtained in terms of LMI, which is less conservative than the existing one. A numerical example demonstrates the validity of this approach.
文摘In the process of quantifying optimum seismic design parameters, the losses implying the failure of the system must be assessed. Intangibles such as human lives may lie among indirect losses. In this paper, we propose a model to calculate the value of the investment that society should be willing to make for saving lives. In order to do this, we analyze both individual and social problems. However, special treatment is given to the individual problem where the value of the life of a human being is inferred by what the person should be willing to pay or willing to accept to reduce the risk of dying. Due to the use of utility curves in the calculation of this kind of intangible, we pay special attention to shape and requirement conditions of these curves. We also pay attention when personal impact and legacies or bequests are considered in utility curves. The results are shown through some applications, especially in the computation of optimum seismic design coefficients at a low seismicity site.
文摘Reliability-based design (RBD) is being adopted by geotechnical design codes worldwide, and it is therefore necessary that rock engineering practice evolves to embrace RBD. This paper examines the Hoek-Brown (H-B) strength criterion within the RBD framework, and presents three distinct analyses using a Bayesian approach. Firstly, a compilation of intact compressive strength test data for six rock types is used to examine uncertainty and variability in the estimated H-B parameters m and σc, and corresponding predicted axial strength. The results suggest that within- and between-rock type variabilities are so large that these parameters need to be determined from rock testing campaigns, rather than reference values being used. The second analysis uses an extensive set of compressive and tensile (both direct and indirect) strength data for a granodiorite, together with a new Bayesian regression model, to develop joint probability distributions of m and σc suitable for use in RBD. This analysis also shows how compressive and indirect tensile strength data may be robustly used to fit an H-B criterion. The third analysis uses the granodiorite data to investigate the important matter of developing characteristic strength criteria. Using definitions from Eurocode 7, a formal Bayesian interpretation of characteristic strength is proposed and used to analyse strength data to generate a characteristic criterion. These criteria are presented in terms of characteristic parameters mk and σck, the values of which are shown to depend on the testing regime used to obtain the strength data. The paper confirms that careful use of appropriate Bayesian statistical analysis allows the H-B criterion to be brought within the framework of RBD. It also reveals that testing guidelines such as the International Society for Rock Mechanics and Rock Engineering (ISRM) suggested methods will require modification in order to support RBD. Importantly, the need to fully understand the implications of uncertainty in nonlinear strength criteria is identified.
文摘【目的】针对南方污水处理厂运行中普遍存在的低碳氮比(C/N=4.5~6.0)水质特点,探索提升原水碳源利用效率、降低曝气能耗,并实现高效低碳脱氮的调控策略和技术方案。【方法】通过开展5.0 m^(3)/h的中试试验,提出了5段Bardenpho工艺与多级缺氧-好氧(AO)工艺的高效低碳运行优化方案和调控策略,并利用碳排放核算分析,对比了不同生物脱氮工艺的碳排放强度,进而提出了污水强化生物脱氮的优化设计与低碳运行策略。同时,在湖北省某污水处理厂开展了工程应用,以期为未来污水处理厂的生化处理系统减污降碳协同增效提供技术参考。【结果】通过实施多点进水和微氧控制等调控手段,将前置好氧区的溶解氧控制在1.0~1.5 mg/L,后置好氧区控制在2.0~2.5 mg/L,五段Bardenpho工艺和多级AO工艺原水内碳源利用率提高20.95%以上,同时提升了5%~14%的反硝化脱氮效率,并实现了2%~6%的电能节约。经核算,5段Bardenpho工艺和多级AO工艺的总碳排放强度分别为0.229 kg CO_(2)/m^(3)和0.211 kg CO_(2)/m^(3)。【结论】相对于传统厌氧-缺氧-好氧(AAO)工艺,通过对5段Bardenpho工艺和多级AO工艺进行优化调控,成功实现了低碳高效运行,不仅提升了脱氮除磷效果,还同步实现了节能降耗。为显著提升活性污泥工艺的脱氮效率并促进节能减碳,工程设计需前瞻,预留充足设计余量与设施,构建精准灵活的调控框架。通过优化碳源分配、调整混合液回流比、控制污泥浓度及调节溶解氧浓度,确保水质达标,提升效能,实现资源高效利用与碳减排。
