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Fast dc fault detection in high-voltage dc (HVdc) grids is paramount due to the possibility of attaining a severely high fault current within few milliseconds. This article proposes a new traveling-wave (TW) based protection scheme to detect and locate faults in HVdc grids. In contrast to the existing TW-based protection and fault location approaches, the proposed scheme, first, utilizes only the first locally measured TW after the inception of a fault, and, second, focuses on the frequency content and polarity of the TW, rather than its arrival time. The direction of the TW is identified based on the pattern of the current TW waveform. A frequency spectral ratio of the current TW is proposed to identify the fault zone and fault location with high accuracy. The proposed method ensures a detection speed of 50 $\mu$s on overhead lines and 500 $\mu$s on underground cables. A remote backup scheme is coordinated with the primary protection and operates within 1.05 ms, which meets the speed requirement of HVdc grids. The performance of the proposed scheme has been, first, assessed using the CIGRE B4 HVdc test grid under various conditions, and, second, compared to existing single- and two-terminal TW methods.

Maximum power point tracking (MPPT) methods are essential for photovoltaic (PV) systems to take full advantage of the available solar energy. Over the past few years, an increasing number of new MPPT methods have been proposed in the literature, and they show better capability of capturing the maximum power point. The testing and evaluation procedure of any new MPPT method is a crucial step for assessing its robustness and performance. PV panel manufacturers always specify power output tolerances, ranging from ±2% to ±5%. Thus, nonideal factors might dominate the subsystem output and defeat any performance comparison attempt and might lead to inaccurate results. This paper highlights the main shortcomings of previous MPPT testing procedures and proposes a comprehensive testing approach using paired difference tests to evaluate the performance of MPPT. The dual channel bench system demonstrates a systematic framework to deal with the nonideal factors associated with PV manufacturing, quantify experimental data, and correctly illustrate the performance improvement of MPPT. The case study shows that the 1% improvement of MPPT could be easily overshadowed by the nonideal factors shown previously. The proposed test setup and analysis method provide the effective solution for evaluating the MPPT performance.