A joint power control and relay selection scheme is considered for a cooperative and cognitive radio system where a secondary network shares spectrum with the primary network. In the secondary network, two secondary u...A joint power control and relay selection scheme is considered for a cooperative and cognitive radio system where a secondary network shares spectrum with the primary network. In the secondary network, two secondary users （SUs） communicate with each other via an assist relay. The main point is to provide the best system performance to SUs while maintaining the interference power at primary user （PU） under a certain level. Using convex optimization, a closed-form solution is obtained when optimizing the power allocation among the two nodes and relay. Based on this result, a joint power control and relay selection scheme with fewer variable dimensions is proposed to maximize the achievable rate of the secondary system. Simulation results demonstrate that the sum rate of the cognitive two-way relay network increases compared with a random relay selection and fixed power allocation.展开更多
Wind energy sources have different structures and functions from conventional power plants in the power system.These resources can affect the exchange of active and reactive power of the network.Therefore,power system...Wind energy sources have different structures and functions from conventional power plants in the power system.These resources can affect the exchange of active and reactive power of the network.Therefore,power system stability will be affected by the performance of wind power plants,especially in the event of a fault.In this paper,the improvement of the dynamic stability in power system equipped by wind farm is examined through the supplementary controller design in the high voltage direct current(HVDC)based on voltage source converter(VSC)transmission system.In this regard,impacts of the VSC HVDC system and wind farm on the improvement of system stability are considered.Also,an algorithm based on controllability(observability)concept is proposed to select most appropriate and effective coupling between inputs-outputs(IO)signals of system in different work conditions.The selected coupling is used to apply damping controller signal.Finally,a fractional order PID controller(FO-PID)based on exchange market algorithm(EMA)is designed as damping controller.The analysis of the results shows that the wind farm does not directly contribute to the improvement of the dynamic stability of power system.However,it can increase the controllability of the oscillatory mode and improve the performance of the supplementary controller.展开更多
中点电位的平衡控制是中点钳位式三电平拓扑安全可靠运行的关键,但现有文献均未能通过建立精确的数学模型对中点电位漂移的物理机理进行精确分析,控制参数整定困难。该文建立了考虑未知干扰和参数摄动影响的中点钳位式三电平D-STATCOM...中点电位的平衡控制是中点钳位式三电平拓扑安全可靠运行的关键,但现有文献均未能通过建立精确的数学模型对中点电位漂移的物理机理进行精确分析,控制参数整定困难。该文建立了考虑未知干扰和参数摄动影响的中点钳位式三电平D-STATCOM的精确数学模型,利用重复控制与无源性控制相结合的方法实现了基于鲁棒L_2性能准则的电流控制器设计,精确分析了参数摄动导致的有功能量分配不均是中点电位漂移的根本原因。通过零序分量注入,利用直流侧上下端电容器之间的有功能量交换实现了中点电位的平衡控制。通过仿真以及1.14 k V,±400 k Var煤矿供电系统的工程应用,验证了该文所建立模型的准确性以及所提控制算法的可行性和有效性。展开更多
基金supported by the National Natural Science Foundation of China (61250005)Jiangxi Postdoctoral Science Foundation(2013KY07)
文摘A joint power control and relay selection scheme is considered for a cooperative and cognitive radio system where a secondary network shares spectrum with the primary network. In the secondary network, two secondary users （SUs） communicate with each other via an assist relay. The main point is to provide the best system performance to SUs while maintaining the interference power at primary user （PU） under a certain level. Using convex optimization, a closed-form solution is obtained when optimizing the power allocation among the two nodes and relay. Based on this result, a joint power control and relay selection scheme with fewer variable dimensions is proposed to maximize the achievable rate of the secondary system. Simulation results demonstrate that the sum rate of the cognitive two-way relay network increases compared with a random relay selection and fixed power allocation.
文摘Wind energy sources have different structures and functions from conventional power plants in the power system.These resources can affect the exchange of active and reactive power of the network.Therefore,power system stability will be affected by the performance of wind power plants,especially in the event of a fault.In this paper,the improvement of the dynamic stability in power system equipped by wind farm is examined through the supplementary controller design in the high voltage direct current(HVDC)based on voltage source converter(VSC)transmission system.In this regard,impacts of the VSC HVDC system and wind farm on the improvement of system stability are considered.Also,an algorithm based on controllability(observability)concept is proposed to select most appropriate and effective coupling between inputs-outputs(IO)signals of system in different work conditions.The selected coupling is used to apply damping controller signal.Finally,a fractional order PID controller(FO-PID)based on exchange market algorithm(EMA)is designed as damping controller.The analysis of the results shows that the wind farm does not directly contribute to the improvement of the dynamic stability of power system.However,it can increase the controllability of the oscillatory mode and improve the performance of the supplementary controller.
文摘中点电位的平衡控制是中点钳位式三电平拓扑安全可靠运行的关键,但现有文献均未能通过建立精确的数学模型对中点电位漂移的物理机理进行精确分析,控制参数整定困难。该文建立了考虑未知干扰和参数摄动影响的中点钳位式三电平D-STATCOM的精确数学模型,利用重复控制与无源性控制相结合的方法实现了基于鲁棒L_2性能准则的电流控制器设计,精确分析了参数摄动导致的有功能量分配不均是中点电位漂移的根本原因。通过零序分量注入,利用直流侧上下端电容器之间的有功能量交换实现了中点电位的平衡控制。通过仿真以及1.14 k V,±400 k Var煤矿供电系统的工程应用,验证了该文所建立模型的准确性以及所提控制算法的可行性和有效性。
