Based on the output-voltage error function, a novel time discrete modulation technique is proposed for matrix converters （MCs） and time-discrete difference equations of a MC circuit are derived. Switch states of MC ...Based on the output-voltage error function, a novel time discrete modulation technique is proposed for matrix converters （MCs） and time-discrete difference equations of a MC circuit are derived. Switch states of MC are obtained when the output voltage error function is minimized, thus the optimum combination of switch states is derived for the closed-loop control of MC. Meanwhile, advantages of the least calculation workload, the simple process, and the convenient for implementation are brought while switch states are described as space vectors in the α-β coordination system. Simulation and experimental results demonstrate the validity of the time-discrete modulation technique and the feasibility of the control approach.展开更多
Because of the complexity and difficulty of realizing a multi-wavelength soliton state,reports on its internal dynamic characteristics are scarce.In this study,the switching and periodic soliton explosion processes of...Because of the complexity and difficulty of realizing a multi-wavelength soliton state,reports on its internal dynamic characteristics are scarce.In this study,the switching and periodic soliton explosion processes of the multi-wavelength soliton state in a negative dispersion passively mode-locked fiber laser are realized.The generation of the multi-wavelength soliton state undergoes the process of noise,oscillation,and stable mode-locking,and the splitting and annihilation of solitons with different group velocities directly impact the generation and disappearance of three wavelengths.Positive and negative dispersion lead to different group velocities of solitons.The presence and displacement of solitons with different group velocities cause soliton collisions,which lead to soliton explosions.A soliton experiences relative phase oscillation,chaos,and oscillation,as well as convergence and separation before and after an explosion.With an increase in parameters related to pump power,single-soliton oscillation,multi-wavelength solitons,and chaos are found in experiments and simulations,proving the relevance and reliability between simulation and experimental results.This work promotes the dynamical study of multi-soliton collisions in nonlinear science and the development of chaos theory in multi-comb lasers.展开更多
The problem of admissibility analysis and control synthesis of discrete-time switched linear singular （SLS） systems for arbitrary switching laws is solved. By using the switched Lyapunov function approach, some new ...The problem of admissibility analysis and control synthesis of discrete-time switched linear singular （SLS） systems for arbitrary switching laws is solved. By using the switched Lyapunov function approach, some new sufficient conditions under which the SLS system is admissible for arbitrary switching laws are derived in terms of linear matrix inequalities （LMIs）. Based on the admissibility results, control synthesis is then to design switched state feedback and static output feedback controllers, guaranteeing that the resulting closed-loop system is admissible. The presented results can be viewed as the extensions of previous works on switched Lyapunov function approach from the regular switched systems to singular switched cases. Examples are provided to demonstrate the reduced conservatism and effectiveness of the proposed conditions.展开更多
The capacitor is one of the most important compo-nents in a modular multilevel converter(MMC).Due to the chemical process and the aging effect,the capacitor is subject to deterioration over time which is usually manif...The capacitor is one of the most important compo-nents in a modular multilevel converter(MMC).Due to the chemical process and the aging effect,the capacitor is subject to deterioration over time which is usually manifested by a drop in capacitance.To identify the abnormal capacitors and enhance the reliability of MMCs,an improved submodule(SM)capacitor condition monitoring method is proposed in this pa-per.The proposed method estimates the capacitance during each control cycle based on the switching states of SMs,offer-ing advantages such as high accuracy and no adverse influence on the operation of MMCs.Firstly,the aging differences of ca-pacitors in different SMs per arm of MMC are analyzed.Then,the capacitances of SMs that switch on the state are calculated based on the relationship between the capacitor voltage and cur-rent during each control cycle.A data processing algorithm is proposed to improve the accuracy of capacitance estimation.Fi-nally,the simulation and the real-time control hardware-in-the loop test results based on real-time digital simulator(RTDS)show the effectiveness of the proposed method.展开更多
Analyzes the mechanism of overvoltage when contactless tap changer switch which is applied in distributing transformer converted directly.When the device convert the tap off,it employs the way that the SSR is switche...Analyzes the mechanism of overvoltage when contactless tap changer switch which is applied in distributing transformer converted directly.When the device convert the tap off,it employs the way that the SSR is switched on when voltage through zero and switched off when current through zero.But in the experiment we found that overvoltage will occur in the process of changing tap changer.The paper illustrates the mechanism of overvoltage in theory by analyzing the equivalent circuit and using analytic method of transition process.展开更多
An algorithm is proposed for scheduling dependent tasks in time-varying heterogeneous multiprocessor systems, in which computational power and links between processors are allowed to change over time. Link contention ...An algorithm is proposed for scheduling dependent tasks in time-varying heterogeneous multiprocessor systems, in which computational power and links between processors are allowed to change over time. Link contention is considered in the multiprocessor scheduling problem. A linear switching-state space-modeling paradigm is introduced to enable theoretical analysis from a system engineering perspective. Theoretical analysis of this model shows its robustness against changes in processing power and link failure. The proposed algorithm uses a fuzzy decision-making procedure to handle changes in the multiprocessor system. The efficiency of the proposed algorithm is illustrated by several random experiments and comparison against a recent benchmark approach. The results show up to 18% average improvement in makespan, especially for larger scale systems.展开更多
In this paper,we study the dynamical behavior of a stochastic host-generalist parasitoid model with Holling II functional response.First,by constructing a suitable Lyapunov function,we prove that the stochastic system...In this paper,we study the dynamical behavior of a stochastic host-generalist parasitoid model with Holling II functional response.First,by constructing a suitable Lyapunov function,we prove that the stochastic system has a unique ergodic stationary distribution under certain condition.Second,we analyze the stationary probability density when the corresponding deterministic system has a unique stable positive equilibrium.The original stochastic system is transformed to an Itôaverage diffusion system by using Taylor expansions at the positive equilibrium point,polar coordinate transformation and stochastic average method.Then the stationary probability density is obtained by solving the Fokker-Planck equation of the average diffusion system.Finally,we explore noise-induced state transitions between two random attractors in the bistable regions:(i)between two internal stable equilibria;(ii)between an internal equilibrium and a limit cycle.The critical noise intensity for which the state switching occurs is estimated by calculating confidence ellipses.The results show that large environmental fluctuations can obviously affect the stability of ecosystems,and cause transitions between high and low biomass of the hosts and the generalist parasitoids.展开更多
文摘Based on the output-voltage error function, a novel time discrete modulation technique is proposed for matrix converters （MCs） and time-discrete difference equations of a MC circuit are derived. Switch states of MC are obtained when the output voltage error function is minimized, thus the optimum combination of switch states is derived for the closed-loop control of MC. Meanwhile, advantages of the least calculation workload, the simple process, and the convenient for implementation are brought while switch states are described as space vectors in the α-β coordination system. Simulation and experimental results demonstrate the validity of the time-discrete modulation technique and the feasibility of the control approach.
基金supported by the National Natural Science Foundation of China(Grant Nos.12261131495,12075210,and 12275240)the Scientific Research and Development Fund of Zhejiang A&F University(Grant No.2021FR0009)。
文摘Because of the complexity and difficulty of realizing a multi-wavelength soliton state,reports on its internal dynamic characteristics are scarce.In this study,the switching and periodic soliton explosion processes of the multi-wavelength soliton state in a negative dispersion passively mode-locked fiber laser are realized.The generation of the multi-wavelength soliton state undergoes the process of noise,oscillation,and stable mode-locking,and the splitting and annihilation of solitons with different group velocities directly impact the generation and disappearance of three wavelengths.Positive and negative dispersion lead to different group velocities of solitons.The presence and displacement of solitons with different group velocities cause soliton collisions,which lead to soliton explosions.A soliton experiences relative phase oscillation,chaos,and oscillation,as well as convergence and separation before and after an explosion.With an increase in parameters related to pump power,single-soliton oscillation,multi-wavelength solitons,and chaos are found in experiments and simulations,proving the relevance and reliability between simulation and experimental results.This work promotes the dynamical study of multi-soliton collisions in nonlinear science and the development of chaos theory in multi-comb lasers.
基金supported partly by the National Natural Science Foundation of China(6057400660835001)+1 种基金the Key Project of Chinese Ministry of Education(108060)the Jiangsu Planned Projects for Postdoctoral Research Funds(0802010c).
文摘The problem of admissibility analysis and control synthesis of discrete-time switched linear singular （SLS） systems for arbitrary switching laws is solved. By using the switched Lyapunov function approach, some new sufficient conditions under which the SLS system is admissible for arbitrary switching laws are derived in terms of linear matrix inequalities （LMIs）. Based on the admissibility results, control synthesis is then to design switched state feedback and static output feedback controllers, guaranteeing that the resulting closed-loop system is admissible. The presented results can be viewed as the extensions of previous works on switched Lyapunov function approach from the regular switched systems to singular switched cases. Examples are provided to demonstrate the reduced conservatism and effectiveness of the proposed conditions.
基金This work was supported in part by the Joint Funds of the National Natural Science Foundation of China(No.U22B6006).
文摘The capacitor is one of the most important compo-nents in a modular multilevel converter(MMC).Due to the chemical process and the aging effect,the capacitor is subject to deterioration over time which is usually manifested by a drop in capacitance.To identify the abnormal capacitors and enhance the reliability of MMCs,an improved submodule(SM)capacitor condition monitoring method is proposed in this pa-per.The proposed method estimates the capacitance during each control cycle based on the switching states of SMs,offer-ing advantages such as high accuracy and no adverse influence on the operation of MMCs.Firstly,the aging differences of ca-pacitors in different SMs per arm of MMC are analyzed.Then,the capacitances of SMs that switch on the state are calculated based on the relationship between the capacitor voltage and cur-rent during each control cycle.A data processing algorithm is proposed to improve the accuracy of capacitance estimation.Fi-nally,the simulation and the real-time control hardware-in-the loop test results based on real-time digital simulator(RTDS)show the effectiveness of the proposed method.
基金Harbin science an technology officecontract num ber is 0 0 112 110 98
文摘Analyzes the mechanism of overvoltage when contactless tap changer switch which is applied in distributing transformer converted directly.When the device convert the tap off,it employs the way that the SSR is switched on when voltage through zero and switched off when current through zero.But in the experiment we found that overvoltage will occur in the process of changing tap changer.The paper illustrates the mechanism of overvoltage in theory by analyzing the equivalent circuit and using analytic method of transition process.
文摘An algorithm is proposed for scheduling dependent tasks in time-varying heterogeneous multiprocessor systems, in which computational power and links between processors are allowed to change over time. Link contention is considered in the multiprocessor scheduling problem. A linear switching-state space-modeling paradigm is introduced to enable theoretical analysis from a system engineering perspective. Theoretical analysis of this model shows its robustness against changes in processing power and link failure. The proposed algorithm uses a fuzzy decision-making procedure to handle changes in the multiprocessor system. The efficiency of the proposed algorithm is illustrated by several random experiments and comparison against a recent benchmark approach. The results show up to 18% average improvement in makespan, especially for larger scale systems.
文摘In this paper,we study the dynamical behavior of a stochastic host-generalist parasitoid model with Holling II functional response.First,by constructing a suitable Lyapunov function,we prove that the stochastic system has a unique ergodic stationary distribution under certain condition.Second,we analyze the stationary probability density when the corresponding deterministic system has a unique stable positive equilibrium.The original stochastic system is transformed to an Itôaverage diffusion system by using Taylor expansions at the positive equilibrium point,polar coordinate transformation and stochastic average method.Then the stationary probability density is obtained by solving the Fokker-Planck equation of the average diffusion system.Finally,we explore noise-induced state transitions between two random attractors in the bistable regions:(i)between two internal stable equilibria;(ii)between an internal equilibrium and a limit cycle.The critical noise intensity for which the state switching occurs is estimated by calculating confidence ellipses.The results show that large environmental fluctuations can obviously affect the stability of ecosystems,and cause transitions between high and low biomass of the hosts and the generalist parasitoids.
