Adaptive full-order observer is widely used for speed-sensorless control of induction motors. However, it is unstable at low speed. To address this problem, this paper proposes an improved speed-adaptive law and introduces a feedback gain matrix into the system with improved speed-adaptive law. The improved speed-adaptive law is obtained by local linearization of the rotor flux distribution on the estimated rotating coordinate system. This method can improve the observation accuracy of speed. Furthermore, the introduction of the feedback gain matrix can make the poles of the observer far away from the imaginary axis and increase the dynamic performance of the system. Comparative study shows that the proposed method has better stability. The simulation results verify the effectiveness and feasibility of this method.
China's land space planning requires the power sector to carry out the spatial layout planning of distribution power grid. So it is necessary to research the regularity and rationality of urban distribution power grids in spatial distribution. In this paper, reasonable quantitative indicators are defined to measure how well grid planning and space layout match up. Firstly, we consider the topological characteristics of urban grid. The homogeneity and agglomeration of the grid in spatial distribution are quantified based on the fractal dimension, in order to evaluate the consistency between the urban built-up regions, roadways and the grid. Secondly, we consider the electrical characteristics of the grid. A weighted box dimension is created based on territorial load to evaluate the consistency between the urban built-up regions and the grid. Finally, the defined quantitative indicators are applied to the consistency evaluation of the actual grid structure and the geographical spatial layout in a certain area, which verifies the rationality and feasibility of the proposed method.
In order to solve the problems of power jump caused by direct switching between energy storage frequency regulation control modes in critical mode and the limitation of energy storage output caused by too high or too low State of Charge（SOC）of energy storage,an integrated control strategy of energy storage participating in primary frequency regulation based on fuzzy control is proposed.Firstly,the influence of energy storage virtual droop,virtual inertia and virtual negative inertia control parameters on the frequency response of the system is analyzed,and the frequency modulation advantage and stable variation range of each control parameter are determined;Secondly,a fuzzy controller with virtual negative inertia control is designed to realize smooth switching and complementary advantages between control modes and accelerate frequency recovery;Finally,the feedback control strategy of SOC and the selfrecovery control strategy of energy storage SOC are designed by using the logistics function,so that the energy storage capacity can be better maintained and the frequency modulation ability of energy storage can be improved. The effectiveness of the proposed strategy is verified by Matlab/Simulink simulation.
电网发生故障后充分利用报警信息对故障元件进行判别,是保障电力系统安全运行的重要环节.针对现有Petri网时序推理与置信度推理相分开、计算过程复杂且未充分利用时间信息等问题,提出了一种基于加权模糊的时序约束Petri网电网故障诊断方法.将时序约束引入到Petri网的库所与变迁中,根据保护与断路器之间的动作顺序关系建立加权模糊的时序约束Petri网模型.定义置信度与时间区间分层推理运算,实现置信度推理与时序推理同步进行,在置信度推理过程中充分考虑到时间信息的影响.通过对多组算例仿真比较得出,所提方法能够有效判别出故障元件,具有较高的准确性和容错性.
针对大规模可再生能源并网发电产生的不确定性问题,提出计及条件风险价值(CVaR)的含光热电站(CSP)的鲁棒机组组合模型.首先,建立了CSP机组持续且稳定供电的数学表达;然后,引入CVaR概念用于度量不确定风电给调度运行带来的风险损失,建立计及CVaR的含CSP的鲁棒机组组合模型,构造包含区间、时间和空间的多维不确定性集合,实现对风力发电的不确定性调节;最后,以IEEE 6节点和IEEE 118节点系统为例,验证了模型的有效性.
