The concept of a microgrid has drawn the interest of research community in recent years. The most interesting aspects are the integration of renewable energy sources and energy storage systems at the consumption level, aiming to increase power quality, reliability and efficiency. On top of this, the increasing of DC-based loads has re-open the discussion of DC vs AC distribution systems. As a consequence a lot of research has been done on DC distribution systems and its potential for residential applications. This paper presents an overview of the LVDC distribution systems used in residential applications. Several publications that study the potential energy savings and overall advantages of the LVDC distribution systems are analysed. Different power architectures and topologies are discussed. The existing demonstration facilities where LVDC distribution systems have been implemented are also shown.

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An overview of low voltage DC distribution systems for residential applications

India is a power deficit country and one third of its homes are off grid or near off grid. This paper presents an efficient and affordable Solar DC solution for powering such homes. Though several solutions have emerged in the past for powering these homes, those have been expensive and energy inefficient. These solutions rely on several DC to AC and AC to DC conversions, to feed the widely used AC home loads, thus, wasting a large chunk of the expensive power. The proposed Solar DC solution for off-grid homes (OGH) is developed to use the generated PV power efficiently. With this solution, the panel and battery size is reduced by 2 to 2.5 times and the cost to power a house is reduced to nearly half the cost of the existing solutions. The paper also presents a techno-economic comparison between the proposed OGH solution with some existing solar systems.

Solar-DC deployment experience in off-grid and near off-grid homes: Economics, technology and policy analysis

The use of green energy sources to feed DC microgrids is gaining prominence over traditional centralised AC systems. DC microgrids are characterised by the use of intermediate DC-DC converter which acts as power conditioning units. Hence, the choice of an appropriate DC-DC converter becomes significant as the overall system efficiency is strongly dependent on the converter’s performance. This paper proposes a novel high gain high power (HGHP) DC-DC converter for DC microgrid, which is of one of the significant step forward in the development of DC microgrids. The suitability of the proposed HGHP DC-DC converter is demonstrated by experimental tests of the 60V/1.1kV, 3kW converter; test results validate the converter’s suitability for DC distribution. A significant number of performance parameters of the proposed converter is compared with state of the art converter topologies demonstrating the superior capabilities of the proposed converter. This paper also portrays the potential benefits that could be reaped by trending towards DC instead of existing AC system. The advantages and challenges to be confronted in the foreseeable future while implementing sustainable DC microgrids are also highlighted. Finally, this paper encapsulates renewable energy fed DC microgrid system as an appropriate, technically feasible, economically viable and competent solution for efficiently utilising the sustainable energy sources.

/pdf/high-gain-high-power-hghp-dc-dc-converter-for-dc-microgrid-39eaols47y.pdf

High gain - high power (HGHP) DC-DC converter for DC microgrid applications: design and testing

In the pursuit of incentivising photovoltaic (PV) installations at a household level, this paper presents a nanogrid control system that utilizes thermostatically controlled loads (TCLs) to increase the correlation between power consumption and PV production The maximum power point tracking signal is used to implement instantaneous control based on PV power availability, as the TCLs are used to store thermal energy and shift consumption A model of the nanogrid has been created and simulated under a variety of load and solar irradiance conditions The results show the system can reduce power purchased from the grid by 44%

Use of Maximum Power Point Tracking Signal for Instantaneous Management of Thermostatically Controlled Loads in a DC Nanogrid

Various statistics indicate that many of the parts of India, especially rural and island areas have either partial or no access to electricity. The main reason for this scenario is the immense expanse of which the power producing stations and the distribution hubs are located from these rural and distant areas. This emphasizes the significance of subsidiarity of power generation by means of renewable energy resources. Although in current energy production scenario electricity supply is principally by AC current, a large variety of the everyday utility devices like cell phone chargers, computers, laptop chargers etc. all work internally with DC power. The count of intermediate energy transfer steps are significantly abridged by providing DC power to mentioned devices. The paper also states other works that prove the increase in overall system efficiency and thereby cost reduction. With an abundance of solar power at disposal and major modification in the area of power electronic conversion devices, this article suggests a DC grid that can be used for a household in a distant or rural area to power the aforementioned, utilizing Solar PV. A system was designed for a household which is not connected to the main grid and was successfully simulated for several loads totaling to 250 W with the help of an isolated flyback converter at the front end and suitable power electronic conversion devices at each load points. Maximum abstraction of operational energy from renewable sources at a residential and commercial level is intended with the suggested direct current systems.

https://www.mdpi.com/1996-1073/12/11/2157/pdf

DC Grid for Domestic Electrification

Lighting, fans and electronic devices form a significant and growing portion of power-load at homes and need power back-up support in case there are frequent power-cuts. A Diesel generator is generally used today in multi-storied buildings to provide this backup. The DC system, proposed in this paper, provides a far more energy-efficient alternative using renewable power-source for backup. It creates a pull for a home to move towards far more energy efficient DC loads. The solution provides a GREEN option to the existing solution. This paper provides a fresh perspective on the problem of eliminating conversion losses for uninterrupted operation of DC appliances. A cost benefit analysis shows that this DC system can reduce costs to the consumer by eliminating the complex electronics embedded in the inversion process. A rough measurement of the conversion losses for commercially available inverters and battery chargers illustrates that gains of 30% to 45% are easily obtainable

Uma Rajesh

Papers

Economic analysis of deployment of DC power and appliances along with solar in urban multi-storied buildings