Alternating current (AC) microgrids are expected to operate as active components within smart distribution grids in the near future. The high penetration of intermittent renewable energy sources and the rapid electrification of the thermal and transportation sectors pose serious challenges that must be addressed by modern distribution system operators. Hence, new solutions should be developed to overcome these issues. Microgrids can be considered as a great candidate for the provision of ancillary services since they are more flexible to coordinate their distributed generation sources and their loads. This paper proposes a method for compensating microgrid power factor and loads asymmetries by utilizing advanced functionalities enabled by grid tied inverters of photovoltaics and energy storage systems. Further, a central controller has been developed for adaptively regulating the provision of both reactive power and phase balancing services according to the measured loading conditions at the microgrid’s point of common coupling. An experimental validation with a laboratory scale inverter and a real time hardware in the loop investigation demonstrates that the provision of such ancillary services by the microgrid can significantly improve the operation of distribution grids in terms of power quality, energy losses and utilization of available capacity.

Several space organizations have been planning to establish a permanent, manned base on the Moon in recent years. Such an installation demands a highly reliable electrical power system (EPS) to supply life support systems and scientific equipment and operate autonomously in a fully self-sufficient manner. This paper explores various technologies available for power generation, storage, and distribution for space microgrids on the Moon. Several factors affecting the cost and mass of the space missions are introduced and analysed to provide a comprehensive comparison among the available solutions. Besides, given the effect of base location on the design of a lunar electrical power system and the mission cost, various lunar sites are introduced and discussed. Finally, the control system requirements for the reliable and autonomous operation of space microgrids on the Moon are presented. The study is complemented by discussing promising future technological solutions that could be applied upon a lunar microgrid.

The present study analyses the design of the power system of a manned lunar base, in Shackleton crater, using well-established terrestrial technologies deriving from DC microgrids with increased fault-tolerance needs. Expected luminance data from 2020 is used in order to select the ideal base location in terms of mean annual solar irradiance, according to which, the sizing of the power generation and storage units is performed. The proposed grid topology is meshed in order to satisfy the high reliability requirements of a manned space mission and, at the same time, to reduce the mass/ volume budgets of the mission. The load profile is constructed using a set of notional loads. Furthermore, a novel solar array configuration is proposed under the scope of maximizing the energy production under the specific irradiance of the base siting. After preliminary sizing is performed, a series of microgrid-related technologies is suggested, covering all levels of grid design, control and protection.

This paper presents a fault-tolerant secondary and adaptive primary microgrid control scheme using a hybrid multiagent system (MAS), capable of operating either in a semi-centralised or distributed manner. The proposed scheme includes a droop-based primary level that considers the microgrid energy reserves in production and storage. The secondary level is responsible for: a) the microgrid units' coordination, b) voltage and frequency restoration and c) calculation of the droop/ reversed-droop coefficients. The suggested architecture is arranged upon a group of dedicated asset agents that collect local measurements, take decisions independently and, collaborate in order to achieve more complex control objectives. Additionally, a supervising agent is added to fulfill secondary level objectives. The hybrid MAS can operate either with or without the supervising agent operational, manifesting fast redistribution of the supervising agent tasks. The proposed hybrid scheme is tested in simulation upon two separate physical microgrids using three scenarios. Additionally, a comparison with conventional control methodologies is performed in order to illustrate further the operation of a hybrid approach. Overall, results show that the proposed control framework exhibits unique characteristics regarding reconfigurability and fault-tolerance, while power quality and improved load sharing are ensured even in case of critical component failure. PF min minimum power factor (-) m f-P droop coefficient (Hz/W) n V-Q droop coefficient (Hz/VAr) v ocd compensating d-axis voltage by virtual impedance (V) v ocq compensating q-axis voltage by virtual impedance (V) i od inverter output inductor current on the d-axis (A) i oq inverter output inductor current on the q-axis (A) R v resistive part of the virtual impedance (Ω) L v inductive part of the virtual impedance (H) M on exchanged agent messages during one operation cycle-MGCC operational (-) M off exchanged agent messages during one operation cycle-MGCC inactive (-) N ESS total number of ESSs in a microgrid (-) N PV total number of PVs in a microgrid (-) N Load total number of load buses in a microgrid (-) E nom Nominal Battery Capacity (Wh)