Energies

This paper presents a cascaded control strategy for neutral-point-clamped three-level (NPC-3L) inverter-fed permanent magnet synchronous motors (PMSMs), integrating continuous-control-set model-predictive control (CCS-MPC) with mid-point voltage regulation and an online Lyapunov-stable neural-network (NN) disturbance observer. The outer CCS-MPC loop optimizes voltage vector application for accurate current tracking and harmonic suppression, while the inner loop balances mid-point voltage by adjusting the dwell times of P/N small-voltage vectors (VVs). The NN-based disturbance observer compensates parameter mismatches in real time, reducing steady-state dq-axis current errors. To validate the effectiveness of the proposed strategy, experiments are conducted using a three-phase PMSM fed by three-phase NPC-3L inverters. Experimental results demonstrate substantial improvements in mid-point voltage balance, current quality, and robustness against model uncertainties.

This paper focuses on assessing different sustainable energy generation and storage systems for residential buildings in Spain, identifying the best-performing system according to the end-user requirements. As outlined by the consulted literature, the authors have selected two types of hybrid configurations—a Photovoltaic System with Battery Backup (PSBB) and a Photovoltaic System with Hydrogen Hybrid Storage Backup (PSHB)—and a Grid-Based System with Renewable Hydrogen Contribution (GSHC) is proposed. A Fuzzy Analytical Hierarchy Process methodology (FAHP) is employed for evaluating the hybrid power systems from a multi-criteria approach: acquisition, operational, and environmental. The main requirements for selecting the optimal system are organized under these criteria and evaluated using key performance indicators. This methodology allows the selection of the best option considering objective and subjective system performance indicators. Beyond establishing the ranking, a sensitivity analysis was conducted to provide insights into how individual criteria influence the ranking of the hybrid power systems alternatives. The results demonstrate that the selection of hybrid power systems for a residential building is highly dependent on consumer preferences, but the PSBB system scores highly in operation and acquisition criteria, while the GSHC has good performance in all the criteria.

In order to realize the wide frequency applicability of the electromagnetic current transformer in a ‘double high’ power system, the equivalent circuit model of the electromagnetic current transformer under wide frequency is established. The complex permeability method is used to obtain the excitation impedance value on the basis of the existing core parameters. Secondly, according to the equivalent circuit of the current transformer in the broadband domain, the error transfer function of the electromagnetic current transformer is derived. Through simulation calculation, the ratio difference and angle difference in the electromagnetic current transformer at 50 Hz–3000 Hz are obtained. The correctness of the theoretical analysis and simulation model is verified by comparing it with the existing model and measurement. The simulation and test results show that the electromagnetic current transformer has good linearity when the frequency is in the frequency range of 50 to 650 Hz. When the frequency exceeds this frequency, the ratio difference and angle difference in the current transformer will not reach the accuracy standard, which indicates that it is difficult to accurately measure the high frequency current. Aiming at the correlation of frequency characteristics, this paper proposes a method of optimizing parameters, which provides a certain reference for the error compensation and structural design of electromagnetic current transformers.

To handle the uncertainties brought by the increasing penetration of renewable energy sources and random loads, we design a stochastic multi-timescale distribution network reconfiguration (SMTDNR) framework to coordinate diverse scheduling resources across different timescales and develop an efficient heuristic algorithm to solve this complex NP-hard combinatorial optimization problem with high efficiency for medium- and high-voltage distribution networks. First, the SMTDNR problem, incorporating distributed renewable generators, fuel generators, energy storage systems, and controllable loads, is simplified through circular constraint linearization, Jabr relaxation, and second-order cone (SOC) relaxation techniques. Then, a one-stage multi-timescale successive branch reduction (MTSBR) algorithm is developed for distribution networks with one redundant branch, which transforms the SMTDNR problem into a stochastic multi-timescale optimal power flow (SMTOPF) problem. This is extended to a two-stage MTSBR algorithm for general networks with multiple redundant branches, which iteratively runs the proposed one-stage MTSBR algorithm. Numerical results on modified IEEE 33-bus and 123-bus distribution networks validate the superior optimality, feasibility, and computational efficiency of the proposed algorithms, particularly in scenarios of high renewable penetration and increased uncertainty, offering robust and feasible solutions where traditional methods may fail.