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The use of synchronized measurement technology leads to a more reliable and secure operation of the power system. Phasor calculation is needed for all buses where a phasor measurement unit is installed, and fast and precise estimation is necessary for accurate monitoring, protection and control. The Prony algorithm is one promising method due to its capability to estimate phasor adaptively with changing frequency. The algorithm projects the signal on $L$ exponentially damped sine functions, where $L$ is the order of the Prony. However, the order under different conditions should be adapted automatically to reduce computation time. To adaptively specify the order, the empirical mode decomposition (EMD) method is proposed in this paper to be combined with the Prony and named EMD-Prony. The EMD decomposes a signal into finite single oscillatory modes, representing the number of modes in the signal. EMD is also used as a pre-processing step to filter noise from an input signal of Prony. Therefore, EMD is proposed here as an assistant of Prony in a phasor estimation. Finally, the proposed method is tested on the benchmark signals proposed in the IEEE standard, signals obtained from a simulated power system, and measured data from a real-world power system. [ABSTRACT FROM AUTHOR]

The dual-active-bridge (DAB) is a typical topology of dc–dc converter for bus connection, voltage conversion, power transmission, and electrical isolation in dc power grids. The open-circuit switching fault (OCSF) may threaten the safe operation of DAB and should be eliminated in time. However, the researches on parasitic parameters mainly focus on traditional dc–dc converters, and there are still few discussions on parasitic parameters in the high-frequency dc–dc converter such as DAB. The power components are usually considered without parasitic parameters in OCSF analysis and tolerant control, leading to deviations in modality analysis and practical control for DAB. To solve this issue, the modality analysis considering parasitic parameters during OCSF in DAB is investigated, and the sneak circuits and electrical characteristics with parasitic parameters are discussed in this article. Besides, to realize fault tolerance for DAB during OCSF considering parasitic parameters, a new fault tolerance control strategy including modeling, topology transformation principle, and practical control architecture are also proposed. Compared with conventional fault tolerance strategy, the proposed strategy will be more efficient, rapid and feasible for DAB during OCSF process. The experimental results in DAB prototype verify correctness and effectiveness of analysis and proposed strategy. [ABSTRACT FROM AUTHOR]

Input-series-output-parallel (ISOP) isolated bidirectional direct current (dc)/dc converter (IBdc) becomes a preferred scheme connecting high-voltage and low-voltage bus in dc distribution network. Input-voltage-sharing (IVS) among modules is essential to realize the stable operation of ISOP system. Nowadays, with large-scale access of distributed energy sources and loads in dc grids, the fluctuations in bus voltage and connected load become frequent and great, deteriorating the IVS performance and stable operation of ISOP structure IBdc. To solve this issue, a triple-close-loop IVS strategy is proposed in this article. Compared with the conventional IVS strategy with constant input impedance, the proposed IVS strategy reshapes input impedance to be a full-order model containing high-order components and sensitive to fluctuation of output voltage, and IVS control based on reshaped impedance improves dynamics feature, maintains ideal output power, and avoids false protection and potential instability for ISOP structure IBdc under frequent and large fluctuation. Experimental results verify the correctness and effectiveness of the analysis and proposed strategy, providing a feasible, efficient, and practical control scheme for ISOP system in dc distribution network. [ABSTRACT FROM AUTHOR]