With the increase of non-linear loads in power grid and the development of power electronics, the growing serious harmonic pollution has put forward higher requirements for the accuracy and real-time performance of th...
With the increase of non-linear loads in power grid and the development of power electronics, the growing serious harmonic pollution has put forward higher requirements for the accuracy and real-time performance of the measurement method. For this problem, this paper proposes a wide-frequency harmonic signal measurement method based on window interpolation FFT and adaptive neural network. After the window function is selected, the frequency of harmonic is estimated by double-spectrum-line interpolation algorithm based on three-term third derivative Nuttall window, and then the smoothed frequencies are input into RLS-Adaline neural network to estimate the amplitude and phase of each harmonic. The simulation results show that the proposed method has higher measurement accuracy and stability under few data conditions and low signal-to-noise ratios than conventional window interpolation algorithms. High accuracy measurement of harmonics with short time window in the range of 0∼2.5kHz is effectively realized.
During the transitional period of UHV network construction, the power grid's characteristics of 'Strong DC and Weak AC' are prominent. Moreover, the high penetration of renewable energies has made the char...
During the transitional period of UHV network construction, the power grid's characteristics of 'Strong DC and Weak AC' are prominent. Moreover, the high penetration of renewable energies has made the characteristics of power systems profoundly changed facing high operation risks. The security and stability control technologies need to be reviewed considering current development situations and combine the characteristics of the grid to make innovation. This paper analyses the development and status quo of stability control technologies from the security and stability control systems which belong to the second defense line. Moreover, frequency and voltage emergency control devices and out-of-step separation devices which belong to the third defense line, as well as features of the security and stability control devices are investigated. According to the planning and development of the future power grid, the development directions of the security control technology is pointed out.
近年来，混合多端直流输电系统快速发展。但是，在混合直流系统中应用的电压源换流器（voltage-source converter, VSC）出口不再需要直流滤波器。此外，考虑到其直流故障电流可被换流器自身有效抑制，直流线路两端也不再需要安装限流电抗器。这意味着线路两端边界缺失，导致应用于常规高压直流输电（line commutated converter based high-voltage direct current, LCC-HVDC）系统和柔性直流（VSC-HVDC）电网的单端量保护均无法适用于混合多端直流输电系统。为此，本文提出了一种适用于混合多端直流输电系统的单端量保护新原理，该方法主要基于暂态信息和主动注入思想实现故障辨识。与应用于LCCHVDC和VSC-HVDC系统的单端量保护相比，所提方法无需依赖线路两端的边界元件，因此更加适用于混合多端直流系统。大量的仿真算例充分验证了所提方法的可行性和优越性。
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