Entity

Time filter

Source Type


Zhang M.,Tongji University | Lin X.,Tongji University | Sun H.,Shanghai Electrical Group Co.
Zhongguo Dianji Gongcheng Xuebao/Proceedings of the Chinese Society of Electrical Engineering | Year: 2014

In the future renewable electric energy delivery and management (FREEDM) microgrid, there will be circulating currents among solid state transformers (SSTs) due to the voltage differences and disproportionate output impedances, particularly in the islanding mode. The output voltage differences were fed back to reduce the errors of their phases and amplitudes in the droop controller. Meanwhile, the adjustable virtual impedance based on the fuzzy control is adopted to make the output impedance of SST match its rated power more exactly using instantaneous circulating current feedback. Simulations and analysis show that the control strategy can restrain the circulating currents well, and can improve the output voltage stability of SST. future renewable electric energy delivery and © 2014 Chin. Soc. for Elec. Eng. Source


Jia T.,East China University of Science and Technology | Jia T.,Shanghai Electrical Group Co. | Niu Y.,East China University of Science and Technology | Zou Y.,East China University of Science and Technology
Information Sciences | Year: 2012

This paper investigates the problem of sliding mode control for stochastic system under the effect of packet dropout. In this work, a new sliding function dependent on the probability of packet dropout is constructed. By means of a Lyapunov function involved in sliding mode variable and system state, both the reachabiltiy and the stability are analyzed simultaneously, and the sufficient condition is derived via linear matrix inequalities. Finally, numerical simulation results are given. © 2012 Elsevier Inc. All rights reserved. Source


Zhang M.,Tongji University | Du Z.,Shanghai Electrical Group Co. | Lin X.,Tongji University | Chen J.,Songjiang Power Supply Company
IEEE Transactions on Smart Grid | Year: 2015

The circulating current among the paralleled solid state transformers (SSTs) originated by the line parameter and mismatched output impedance comes into appearance in the islanded operation of the novel microgrid, the future renewable electric energy delivery and management system. In this regard, the aggregated control strategy of both virtual inductance and external inductance is proposed in this paper to suppress circulating current. The 'matching concept' regarding the parameter selection of virtual and external inductance is proposed to ensure the reliable operation of the system through constructing the complete small-signal model of SST. On the basis of aggregated control strategy and small-signal model, the adaptive virtual impedance control strategy is finally proposed by introducing the feedback of circulating current into the conventional virtual impedance control. The virtual impedance is adjusted adaptively according to the judgment algorithm to regulate the equivalent output impedance of SST. With this modification, the adjustment ability of virtual impedance control against sudden disturbance is improved and the circulating current is further reduced. The simulation results with nonlinear loading are presented to prove that the proposed control strategy, and the parameters determined by the matching concept substantially reduce the circulating current among SSTs and improve the accuracy of load sharing among SSTs. © 2010-2012 IEEE. Source


Du D.,Shanghai University | Fei M.,Shanghai University | Jia T.,Shanghai Electrical Group Co.
Transactions of the Institute of Measurement and Control | Year: 2013

Traditional networked control systems (NCSs) analysis and design have been based on the single closed-loop configuration. This paper studies the modelling and stability of multi-input multi-output (MIMO) networked control systems (NCSs) with multiple channels. Unlike the NCSs based on the single close-loop configuration, there exist data packet dropout, data packet out-of-order and network-induced delay in every channel, which make multi-channel MIMO NCSs more complex. In order to solve these network-related non-deterministic issues, a general switched system model with unknown switched sequence for multi-channel MIMO NCSs is first proposed, which can not only describe the MIMO NCSs where the controller communicates with sensors and actuators through distinct channels, but also can describe the NCSs based on the single closed-loop configuration. Based on Lyapunov stability theory combined with linear matrix inequalities (LMIs) techniques, a sufficient condition is then derived for multi-channel MIMO NCSs to be asymptotical stable in term of a set of bilinear matrix inequalities. Furthermore, the proposed results are easily extended to the uncertain MIMO NCSs. Finally, simulation results confirm the feasibility and effectiveness of the proposed method. © The Author(s) 2011. Source


Niu Y.,East China University of Science and Technology | Liu Y.,East China University of Science and Technology | Jia T.,Shanghai Electrical Group Co.
Optimal Control Applications and Methods | Year: 2013

This paper considers the problem of sliding mode control for uncertain stochastic systems with possible occurrence of actuator faults. There exist parameter uncertainties and state-dependent noise. Moreover, the faults may happen in any of the actuators. The reliable designing on both passive and adaptive sliding mode controllers is investigated, respectively. Both the reachability of the specified sliding surface and the stochastic stability of the sliding motion are analyzed using the stochastic Lyapunov theory. Finally, numerical simulation results are given.Copyright © 2012 John Wiley & Sons, Ltd. Copyright © 2012 John Wiley & Sons, Ltd. Source

Discover hidden collaborations