Frequency control in autonomous microgrids (MG) with high penetration of renewable energy sources represents a great concern to ensure the system stability. In this regard, this paper presents an enhanced control method for battery energy storage systems (BESS) to support the frequency of MG and with the ability of disconnecting from the MG to supplying in the island mode a local consumer. A frequency controller, combining a conventional droop control with an inertia emulation function, governs the BESS active power transfer during the primary frequency control level. The BESS may also provide voltage support in the point of common coupling with the MG. Moreover, the proposed BESS may compensate, partially or totally, the power absorbed by the local loads in order to improve the MG frequency response. When the MG power quality worsens below a certain level, in terms of voltage and frequency, the BESS detaches from the MG and continues to operate islanded. The reconnection is accomplished following a smoothly resynchronization of the local voltage with the MG, without disturbing the local loads supply. Additionally, this paper also discusses about the aspects related to the BESS management and its integration within the proposed system. The simulation and experimental results assess the feasibility of the proposed control solutions.

Progress in Microgrid (MG) research has evolved the MG concept from classical, purely MG power networks to more advanced power and communications networks. The communications infrastructure helps control and manage the unreliable power outputs that most standard power generation elements of the MG (e.g., wind turbines and photo-voltaic panels) deliver. Although communication technologies do offer certain advantages for sensing and control, they generate other complications due to packet loss and packet latency, among other transmission impairments. In this work, we discuss the impact of communications on MG performance, establishing the requirements of data exchanges and system response in the three levels of a hierarchical control approach: primary, secondary, and tertiary. With a focus on the secondary level — responsible for ensuring the restoration of electrical parameters — we identify standards, networking protocols, and communication technologies relevant for the interoperability of MGs and clusters of MGs, including both modes of operation: isolated and grid-connected. We review theoretical approaches and practical implementations that consider the effects of the communications network on the general performance of the MG. Moreover, we undertake an experimental analysis of the influence of wired and wireless communication networks on MG performance, revealing the importance of designing future smart control solutions more robust to communication degradation, especially if wireless technologies are integrated to provide scalable deployments. Aspects such as resilience, security, and interoperability are also shown to require continuing efforts in research and practical applications.

This study analyses the integration impact of battery energy storage systems (BESSs) on the short‐term frequency control in autonomous microgrids (MGs). Short‐term frequency stability relates with the primary or speed control level, as defined in the regulations of the classical grids. The focus is on autonomous MGs that dynamically behave similarly to the classical power systems. This is the systems case with classical distributed generators (DGs), but which can also contain renewable energy sources (RESs) in a certain penetration level. During MG islanded operation, the local generators take over most of the frequency control process, by means of their automatic generation control, which include inertia response and primary control. However, RES‐based DGs are rarely able to provide grid frequency support, as they lack controllability and usually the power conversion chain does not have the possibility of storing and releasing energy when required by the system. Therefore the need of boosting the MG power reserves by adding energy storage systems is often a requirement. The study highlights the improvement in the MG short‐term frequency stability brought by an original BESS control structure enhanced with both inertial response and an adaptive droop characteristic during battery state‐of‐charge limitations. The conducted analysis is accomplished by adopting aggregated models for the involved control mechanisms. The developed model is analysed in frequency domain, whereas an experimental test bench including a real‐time digital simulator with BESS controller in a hardware‐in‐the‐loop structure is used for assessing the system performances.

Charging electric vehicles (EVs) is of great concern both for future vehicle owners and grid operators, with charging at home being the preferred solution by 90% of owners. In addition, the supplied electricity needs to be clean in order to reduce emissions. This paper presents solutions for charging EVs at home using renewable electricity that fulfils such needs. It discusses: (1) the current landscape; (2) the latest hardware developments in the fields of renewable sources and storage; (3) software optimization for home energy management; (4) residential charging station standards and incentives offered by governments; (5) the evolution towards designing smart homes with low energy consumption from the grid; (6) case studies of particular interest.

This paper analyzes the operation of a stand-alone wind turbine system with variable speed Permanent Magnet Synchronous Generator (PMSG) and a Lead Acid Battery (LAB) for energy storage, during wind speed variation. The main purpose is to supply 230 V/50 Hz domestic appliances through a single-phase inverter. The required power for the connected loads can be effectively delivered and supplied by the proposed wind turbine and energy storage systems with an appropriate control method. The control method for obtaining maximum power characteristic of wind turbine (MPPT), monitoring voltage and battery state of charge (SOC) to ensure optimum charging conditions for LAB, are presented. Energy storage devices are required for power balance and power quality in stand alone wind energy systems. Simulations and experimental results validate the stability of the supply.