# Efficiency Comparison of AC and DC Distribution Networks for Modern Residential Localities
## 1 Introduction  
The electric power system started with a battle between two paradigms of AC and DC for power transfer towards the end of the nineteenth century. The earliest power system was DC in nature and AC won the confrontation due to its ability of voltage level transformation [1; 2]. Evidently, if DC had this property at that time, the power system could have been DC in nature. AC developed this property with the invention of electromagnetic transformers. AC enjoyed its rule over all the major stages (generation, transmission, distribution, and utilization) of the power system. DC could not develop a significant presence at that time and was left with dwarfish importance [3]. AC had a pleasant time of command over the power system until the evolution of High Voltage Direct Current (HVDC) transmission, which was proven better as compared to High Voltage Alternating Current (HVAC) transmission with profuse successful installations [4], bringing DC back to the picture of the power system. Generation was a strong ally of AC with three-phase synchronous alternators. DC made its move with the trending renewable energy technologies, threatening AC at the generation end. The solar PV generates DC power; wind farms have a topology, which produces DC at an intermediate stage for conversion to stable and synchronized AC output [5]. Advancement in power electronics enables both conversions between AC and DC as well as voltage level transformation. The power output from solar/wind can effectively be converted to AC for AC dependent loads with power converters [6; 7]. It would not be an exaggeration that power electronics have formed a base for DC to stand on and compete against AC. At the utilization end, the stupendous inflation of modern electronic loads had brought notable demand for DC. The shifting trend towards LED lights,electronics, mobile phone and laptop chargers in the modern home adds to the DC side, strengthening it further as compared to AC [8]. Moreover, lower line losses, lower voltage dips and simplified control associated with the low voltage DC distribution (LVDC) systems have made it an optimal choice for low-cost rural electrification [9; 10; 11; 12; 13; 14]. Figure 1 depicts the penetration of DC in the power system. DC has set up concrete grounds in generation, transmission, and utilization, while distribution is the portion that is still under the research phase. Various aspects of DC in distribution still need to be brought to light. The entire shift towards DC cannot be realized without resolving the technical challenges associated with the emerging DC power systems. These challenges mainly include space charge accumulation in DC cable insulation [15], DC system protection [16], and DC system stability [17]. It should be noted that DC breakers are more sophisticated and cumbersome to manage in the case of short-circuits or unwanted transients. For instance, during a system fault and associated opening of the circuit breakers, the arcing is largely limited in AC due to the zero crossing unlike the case of DC, where forced commutation or energy chopping devices have to be installed to dissipate the arc energy. In DC systems these arcs may be higher and could potentially be hazardous [16]. The existing era is, therefore, witnessing the reignited battle of currents with both the competitors, AC and DC, having their advantages and disadvantages, and thereby motivating the researchers to explore the various factors for comparative analysis. Comparison of AC and DC distribution is the subject of many researchers. For instance, the authors of [18] presented a small-scale network for comparison of AC and DC distribution. They concluded that input savings of 7% can be achieved with DC distribution at 400 V. In [19], the authors presented that conduction losses of DC are 37% of the AC system. Furthermore, [20] presented the loss comparison of DC distribution for two voltage levels (24 V and 48 V), where it was concluded that the DC system with 48 V should be a better choice.