# On Hybrid Nanogrids Energy Management Systems--An Insight into Embedded Systems
## 2 Nanogrids Technologies and Architecture  
### Nanogrids versus Microgrids  
Renewable energy resources are being deployed on a large scale to meet the demands of increasing energy consumption, reduce environmental pollution, and provide socio-economic benefits for sustainable development [49]. Microgrids are enabled by the integration of such distributed energy resources into the utility grid. The idea of a microgrid has been developed to create a self-sufficient system of distributed energy resources that can operate in island mode during grid outages. In a microgrid, an energy management system is required for the intelligent, safe, reliable, and coordinated use of these distributed energy resources. A nanogrid is a single-distribution power system that can operate in stand-alone or grid-connected mode. It consists of local power production, providing local loads with power when needed. It can be used for a single house, a small building, or a small-scale site with the ability to connect or disconnect from other power entities like ESS and/or a control system via controllers and converters [11]. The nanogrid must have at least one local power production unit (renewable sources or fossil fuel-based sources). To ensure the stability of the system, energy storage devices can be used, and they are selected based on many parameters like cost and life cycle. The presence of a controller is also necessary for a nanogrid to coordinate the essential operational strategies [15]. The majority of the world's power transmission is based on AC technology, which has historically replaced DC transmission due to the convenience of transformer-based voltage boosting for long-distance transmission [50, 51]. The choice of AC or DC nanogrids is influenced by several factors, such as the type of energy sources, the type of load, energy storage technology, and regulations. AC nanogrids are more commonly used due to compatibility with the traditional grid and the widespread use of AC appliances, but DC nanogrids are gaining popularity for their simplicity and efficiency in certain applications. DC/ AC converters can be used when energy sources and loads generate or require different types of electrical current. They ensure that the electrical energy generated or stored in a nanogrid can be used to provide power for the loads effectively and efficiently. The major benefit of a DC microgrid is the favorable integration of power electronics, as shown in Figure 2, but AC microgrids are still the main architecture in the field. When various sources and loads, whether AC or DC-based, are connected to the AC grid, a two-stage energy conversion process is typically required. This includes transformations such as AC-DC-AC for sources and AC-DC-DC or AC-DC-AC for loads. Hybrid AC/DC microgrids, which combine AC and DC microgrids, can further reduce the number of conversions within microgrids, thereby maximizing investment costs and efficiency [52, 53]. Hybrid AC/DC microgrids have been the core architecture for land-based distribution systems, including zero and net-zero buildings [54], transport, and energy integration [55, 56], ranging from utility and municipality to military applications. In hybrid AC/DC microgrids, ESSs are essential to achieve both AC and DC sub-grid forming capacity to support AC bus voltage/frequency and DC bus voltage. Multiple hybrid AC/DC microgrid connections can be easily expanded using a modularized design. Compared to traditional AC grids, a hybrid grid system is more efficient. This is particularly important in remote and emergency applications where energy needs to be used as efficiently as possible [57]. The existing research in the nanogrid field can be divided into the following groups: concept, control, hardware, and software. It has received the attention of many researchers in the fields of energy/power management for its important perspectives in power system engineering [12, 58]. According to Energizing Development [59], nanogrids are generally considered to be in the power range of 500 Wp to 10 kWp.