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Yao J.,Chongqing University of Technology | Li H.,Hunan Electrical Power Research Institute | Chen Z.,University of Aalborg | Xia X.,Chongqing University of Technology | And 3 more authors.
IEEE Transactions on Power Electronics | Year: 2013

This paper presents an enhanced control method for a doubly fed induction generator (DFIG)-based wind-power generation system with series grid-side converter (SGSC) under unbalanced grid voltage conditions. The behaviors of the DFIG system with SGSC during network unbalance are described. By injecting a series control voltage generated from the SGSC to balance the stator voltage, the adverse effects of voltage unbalance upon the DFIG, such as stator and rotor current unbalances, electromagnetic torque, and power pulsations, can be removed, and then the conventional vector control strategy for the rotor-side converter remains in full force under unbalanced conditions. Meanwhile, three control targets for the parallel grid-side converter (PGSC) are identified, including eliminating the oscillations in the total active power or reactive power, or eliminating negative-sequence current injected to the grid. Furthermore, a precise current reference generation strategy for the PGSC has been proposed for the PGSC to further improve the operation performance of the whole system. Finally, the proposed coordinated control strategy for the DFIG system with SGSC has been validated by the simulation results of a 2-MW-DFIG-based wind turbine with SGSC and experimental results on a laboratory-scale experimental rig under small steady-state grid voltage unbalance. © 2013 IEEE. Source

Guo J.,Hunan University | Li X.,Hunan University | Deng W.,Hunan Electrical Power Research Institute | He C.,Hunan University | Liu W.,Hunan University
Zhongguo Dianji Gongcheng Xuebao/Proceedings of the Chinese Society of Electrical Engineering | Year: 2013

The optimal allocation of current distributed generations (DG) such as distributed wind generation (DWG) and photovoltaic (PV) is usually single-object oriented, as a result, it is hard to reflect overall benefits of intermittent DGs` optimal allocation. And it is also inappropriate to use fixed variables and constraints to handle the uncertainty and fluctuation of DGs` power output. Aiming to solve the problems, based on the calculation of probabilistic power flow, a bilevel optimal allocation model was established with opportunity-constrained planning method to carry out comprehensive optimal allocation of intermittent DGs and compensation capacitors. And genetic algorithm with elitist strategy was used for the optimal solution. Results of the example demonstrated that optimized operational benefit of compensation capacitors would affect the optimal allocation of DGs and compensation capacitors, and it would be remarkably influenced by compensation capacitors' capacity, maximum daily allowable number of switching operations, seasonal change of the expectation of DGs' output and load power. The optimal scheme of the bilevel planning model considers planning economic benefits of compensation capacitors and DGs, and the optimized operational benefit of compensation capacitors while improving the system voltage quality, thus achieving comprehensive optima of economic benefit and voltage quality. The results of case studies verified the validity and rationality of the model. Source

Wu J.,Hunan Electrical Power Research Institute | Wen J.,Huazhong University of Science and Technology | Sun H.,Huazhong University of Science and Technology | Cheng S.,Huazhong University of Science and Technology
IEEE Transactions on Power Systems | Year: 2012

This paper studies the feasibility of segmenting large power system interconnections with AC link using energy storage technology, similar to the DC link, for improving the system dynamic stability. Firstly, the segmentation validity of the AC interconnected power system using energy storage technology is proved in terms of theoretical analysis, and then a simple and effective control strategy is proposed. Moreover, the influences of the energy storage device location and capacity on the proposed method are discussed in detail. The effectiveness of the proposed method for large AC interconnected power system segmentation is verified by simulations in two AC interconnected power systems. © 2012 IEEE. Source

Ren Z.,Hunan Electrical Power Research Institute | Yu K.,Huazhong University of Science and Technology | Xin Q.,Huazhong University of Science and Technology | Pan Y.,Huazhong University of Science and Technology
IEEE Transactions on Industrial Electronics | Year: 2013

This paper presents the performance of homopolar inductor alternator (HIA) with diode-bridge rectifier and capacitive load. According to the conduction and commutation rules, all the operational modes included in the bridge rectified capacitive load are considered. A simplified average-value mathematical model is established; furthermore, we derive the load characteristic under every operation mode. Using the fundamental machine differential equations and the connecting characteristics between alternator and rectifier, we establish a port-network state model of the system. The performance of the HIA with bridge rectifier and capacitive load can be predicted from charging current, commutating angle, and given parameters of the alternator. Theoretical results are compared with the simulation results obtained from numerical procedure. © 1982-2012 IEEE. Source

He Y.-Q.,Hunan Electrical Power Research Institute
China International Conference on Electricity Distribution, CICED | Year: 2012

A novel network model and a fast algorithm for electrical distribution system (EDS) reliability evaluation considering the random energy output of wind power generators (WPG) are presented in this paper. Firstly, a Switch-Section network model is proposed according to the failure isolation characteristics of switches, and then the Switch-Section network is divided into two kinds of parts, main-network and branch-network, based on the property of the power flow direction when WPG are unavailable. Secondly, the concept of energy influence domain (EID) is proposed in order to consider the random wind energy impact on the power supply range of WPG. Based on this concept, we construct the power supply order which successfully implemented the mapping between the random output of WPG and the supply probability to the sections in the EID. Finally, the reliability indices of the main-network and branch-network are calculated by using properties of elements in upstream and downstream fault propagation. Meanwhile, the impacts of WPG on the sections of its EID are considered when computing the nodal downstream reliability indices. The application of the proposed method to the RBTS-BUS6 demonstrates its validity. And the impacts of the position, load demand characteristics, rated capacity of WPG and wind speed on system reliability are also discussed in detail in this paper which will provide some constructive suggestions to WPG installation. © 2012 IEEE. Source

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