The grid integration of microgrids and the selection of energy management systems (EMS) based on robustness and energy efficiency in terms of generation, storage, and distribution are becoming more challenging with rising electrical power demand. The problems regarding exploring renewable energy resources with efficient and durable energy storage systems demand side management and sustainable solutions to microgrid development to maintain the power system’s stability and security. This article mainly focuses on the overview of the recent developments of microgrid EMS within the control strategies and the implementation challenges of the microgrid. First, it provides energy management strategies for the major microgrid components, including load, generation, and energy storage systems. Then, it presents the different optimization approaches employed for microgrid energy management, such as classical, metaheuristic, and artificial intelligence. Moreover, this article sheds light on the major implementation challenges of microgrids. Overall, this article provides interactive guidelines for researchers to assist them in deciding on their future research.

https://www.mdpi.com/2071-1050/14/22/14794/pdf?version=1668655950

Review of Recent Developments in Microgrid Energy Management Strategies

Hydrogen refueling stations (HRSs) are critical for the popularity of hydrogen vehicles (fuel cell electric vehicles—FCEVs). However, due to high installation investment and operating costs, the proliferation of HRSs is difficult. This paper studies HRSs with on-site electrolytic production and hydrogen storage devices and proposes an optimization method to minimize the total costs including both installation investment and operating costs (OPT-ISL method). Moreover, to acquire the optimization constraints of hydrogen demand, this paper creatively develops a refueling behavior simulation method for different kinds of FCEVs and proposes a hydrogen-demand estimation model to forecast the demand with hourly intervals for HRS. The Jensen–Shannon divergence is applied to verify the accuracy of the hydrogen-demand estimation. The result: 0.029 is much smaller than that of the estimation method in reference. Based on the estimation results and peak-valley prices of electricity from the grid, a daily hydrogen generation plan is obtained, as well as the optimal capacities of electrolyzers and storage devices. As for the whole costs, compared with previous configuration methods that only consider investment costs or operating costs, the proposed OPT-ISL method has the least, 8.1 and 10.5% less, respectively. Moreover, the proposed OPT-ISL method shortens the break-even time for HRS from 11.1 years to 7.8 years, a decrease of 29.7%, so that the HRS could recover its costs in less time.

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Optimized Configuration and Operating Plan for Hydrogen Refueling Station with On-Site Electrolytic Production

At present, which has gradually become a technical development trend that the energy storage grid-connected inverter system is connected to the grid to ensure the stable operation of the whole system. However, the stability of the energy storage system itself is also very important for the safe operation of the power grid. Therefore, improving the stability of grid-connected energy storage system is still the key technology of current research. Aiming at the strong coupling and low-voltage ride-through fault of grid-connected system, a second-order mathematical model of grid-connected control system is established. Based on its state space model, a linear extended state observer (LESO) for state observation and a linear state error feedback (LSEF) control law for disturbance estimation are designed. The second-order linear active disturbance rejection control (LADRC) is introduced into the voltage loop, the stability of the second-order LADRC controller is proved by the Lyapunov stability theory, and the stability conditions are given. Finally, the simulation model of the grid-connected energy storage system is built on the MATLAB/Simulink digital platform, and the low-voltage ride-through fault is designed on the grid-side. The simulation results show that the effect of the second-order LADRC control is better than that of the traditional PI control obviously, which reflects the superiority of the second-order LADRC in controlling the grid-side low-voltage ride-through fault.

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Second-Order Linear Active Disturbance Rejection Control and Stability Analysis of Energy Storage Grid-Connected Inverter

Amorphous metal (AM), specifically amorphous ferromagnetic metal, is considered as a satisfactory magnetic material for exploring electromagnetic devices with high-efficiency and high-power density, such as electrical machines and transformers, benefits from its various advantages, such as reasonably low power loss and very high permeability in medium to high frequency. However, the characteristics of these materials have not been investigated comprehensively, which limits its application prospects to good-performance electrical machines that have the magnetic flux density with generally rotational and non-sinusoidal features. The appropriate characterization of AMs under different magnetizations is among the fundamentals for utilizing these materials in electrical machines. This paper aims to extensively overview AM property measurement techniques in the presence of various magnetization patterns, particularly rotational magnetizations, and AM property modeling methods for advanced electrical machine design and analysis. Possible future research tasks are also discussed for further improving AM applications.

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Characterization of Rotational Magnetic Properties of Amorphous Metal Materials for Advanced Electrical Machine Design and Analysis

Electric motors play a crucial role in modern industrial and domestic applications. With the trend of more and more electric drives, such as electric vehicles (EVs), the requirements for electric motors become higher and higher, e.g., high power density with good thermal dissipation and high reliability in harsh environments. Many efforts have been made to develop high performance electric motors, such as the application of advanced novel electromagnetic materials, modern control algorithms, advanced mathematical modeling, numerical computation, and artificial intelligence based optimization design techniques. Among many advanced magnetic materials, soft magnetic composite (SMC) appears very promising for developing novel electric motors, thanks to its many unique properties, such as magnetic and thermal isotropies, very low eddy current loss, and the prospect of low-cost mass production. This paper aims to present a comprehensive review about the application of SMC for developing various electric motors for electric drives, with emphasis on those with three-dimensional (3D) magnetic flux paths. The major techniques developed for designing the 3D flux SMC motors are also summarized, such as vectorial magnetic property characterization and system-level multi-discipline robust design optimization. Major challenges and possible future work in this area are also discussed.

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A Review of Electric Motors with Soft Magnetic Composite Cores for Electric Drives

Hybrid drive wind power generation system, equipped with the speed regulating differential mechanism (SRDM), is able to be friendly connected to power grid without the need of partly- or fully-rated converters The novel transmission schemes can promote not only the output power quality but also the low voltage ride through (LVRT) capability of the existing wind turbines (WTs) For the purpose of further improving the grid-connected operating performances of SRDM-based WT, this paper aims to develop a hybrid power production unit, in which the hydrogen storage system (HSS), comprising an electrolyzer, a hydrogen fuel cell and a supercapacitor, is integrated into SRDM-based WT The basic architecture and numerical modelling methods of key subsystems in SRDM-based WT as well as in HSS are analyzed After determining the eight different operating modes, a power supervision approach is synthesized for the proposed SRDM-based WT with HSS, by which the power flow management between energy sources and storage elements can be realized Case studies are carried out in the presence of different randomly varying wind speeds and grid voltage faults The satisfactory operating performances of the proposed wind-hydrogen hybrid system in terms of maximizing wind energy utilization, suppressing output power fluctuation and improving system continuous operating stability are verified

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Analysis, Modeling and Control of a Hybrid Drive Wind Turbine with Hydrogen Energy Storage System

One of the keys to the success of the fourth industrial revolution (Industry 4.0) is to empower machinery with cyber–physical systems connectivity. The digital twin (DT) offers a promising solution to tackle the challenges for realizing digital and smart manufacturing which has been successfully projected in many scenes. Electrical machines and drive systems, as the core power providers in many appliances and industrial equipment, are supposed to be reinforced on the verge of Industry 4.0 in the fields of design optimization, fault prognostic and coordinated control. Therefore, this paper aims to investigate the DT modelling method and the applications in electrical drive systems. Firstly, taking the high-speed permanent-magnet machine drive system as an example, multi-disciplinary design fundamentals and technologies, aiming at building initial mechanism and simulation models, are reviewed. The state-of-the-art of DT technologies is figured out to serve for high-precision and multi-scale dynamic modelling, by which a framework for DT models of electrical drive systems is presented. More importantly, fault diagnosis and optimization strategies of electrical drive systems in the decision and application layer are also discussed for the DT models, followed by the conclusions presenting open questions and possible directions.

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Design and Optimization Technologies of Permanent Magnet Machines and Drive Systems Based on Digital Twin Model

This article presents improved iron loss analytical prediction models for interior permanent magnet synchronous motors (IPMSMs) used in electric vehicles. The effects of slotting harmonics, pulsewidth modulation (PWM) carrier harmonics, temperature rise, and mechanical stress are considered in the proposed models. Specifically, by investigating the stator flux density as piecewise linear with trapezoidal waveform, the iron losses in the teeth and yoke regions are calculated separately, considering the different magnetic field distributions and waveforms. To deliberate the PWM harmonic influence, a correction coefficient is added to the hysteresis loss models, while the eddy current loss models are updated by summing all the eddy current losses caused by the power supplying current harmonics. Moreover, the coupling interaction effects of magnetic, thermal, and stress fields on the empirical coefficients of hysteresis and eddy current losses are analyzed in detail and also implemented in the iron loss prediction process. The feasibility and superiority of the proposed models are verified by numerical and experimental case studies on an IPMSM prototype.

Lin Liu

Papers

Analysis, Modeling and Control of a Hybrid Drive Wind Turbine with Hydrogen Energy Storage System

Design and Optimization Technologies of Permanent Magnet Machines and Drive Systems Based on Digital Twin Model

Characterization of Rotational Magnetic Properties of Amorphous Metal Materials for Advanced Electrical Machine Design and Analysis

Improved Iron Loss Prediction Models for Interior PMSMs Considering Coupling Effects of Multiphysics Factors

A Review of Electric Motors with Soft Magnetic Composite Cores for Electric Drives