The Low Voltage Direct Current (LVDC) architecture gives higher benefits over the classic low-voltage alternating current (LVAC) supply concept. LVDC has fewer energy conversion stages, is compatible with renewable energy sources, and is easier to integrate with accumulators. In this paper, an LVDC supply concept is proposed and compared with currently used conventional photovoltaic (PV) systems in terms of efficiency. The new LVDC photovoltaic system behavior is validated using LTspice modeling tool. The findings of this work prove that the concept of LVDC supply is highly attractive when the electricity produced by the photovoltaic is used onsite in the daytime. To carry out an efficient system, the PV power mounted in the houses should be precisely rated with respect to the magnitude of the load energy consumption. We proposed three house examples to verify the superiority of our proposed system in comparison with the traditional LVDC PV chain. An annual analysis of the energy saved by the studied systems was carried out. The main benefit of the suggested LVDC supply is the short way taken by the energy generated by the photovoltaic system to supply DC loads within daytime hours. The registered increase in system efficiency reached more than 20% for the proposed LVDC system.

The solar PV system is used in many power applications, such as clocks, computers, and several devices. It may effectively feed many DC consumers. In the last few years, on-grid PV systems have turned more and more important for power production. In this work, the energy-saving of the suggested LVDC PV chain is confronted with a classical LVDC architecture and the usual (LVAC) PV chain that feeds AC devices. The investigated PV supplies are grid-tied and aimed to feed households and offices.

In the latest years, each academia and industry have grown to be extra interested in LVDC systems. Low-voltage DC structures have numerous advantages over conventional AC structures, such as higher power performance and easier insertion of sustainable supplies. Multiple aspects affecting power quality and reliability enable the use of DC supplies as a replacement for alternating power systems (AC). Exploiting DC rather than AC could put off many energy conversion losses by using auto-consumption of the power generated locally and decreasing power fed by the utility. DC loads including the ones in houses and offices, cooling/heating systems, and large equipment systems including drives have adopted DC electromechanical machines. Because DC circuits don’t have the skin effect or power factor issue, they're more highly efficient than AC circuits [

Subsequently, Lasseter [

LVDC circuit was set up for many years for particular intentions along with aerospace, automobile and marine [

Monte Carlo simulation evaluated DC structures’ technical and monetary feasibility for household use in Texas, dedicated for numerous grid topologies. The network architectures were examined in different cases: one including and another exempt from the storage system. The results show that the use of DC current in the residence can save between 9 and 20% of electricity. Including batteries to store the surplus of solar PV electricity can save 14 to 25% of the energy. Furthermore, DC cooling condensing systems can save energy in the range of 7% and 16% [

Through the previous work [

This paper compares, in terms of energy, the efficiency of the suggested LVDC PV supply with a traditional LVDC architecture and the usual (LVAC) PV chain that feeds AC loads. The paper is structured as follows: within the first part, diverse PV chains are provided. In this section, the benefits of the use of the LVDC supply are depicted. In the second part, the equivalent models of the used semiconductor components are described. These models are used to determine the efficiency of the considered power circuits in the PV systems. The PV panels model, as well as the MPPT technique implementation, are provided in part three of this work; in this section, the computation results of the suggested new PV nanogrid are presented. In the last part of this work, the energy performance of the suggested LVDC supply concept is discussed in comparison with the conventional LVDC architecture. For this purpose, household power demand profiles are studied and the Jeddah site in Saudi Arabia was selected for this analysis.

The conventional LVAC architecture (System 1) associated with a low-voltage grid is presented in

Another frequently exploited LVDC nanogrid (system 2) is shown in

The novel LVDC architecture (system 3) exploits the terminal voltage across the PV panels. This DC voltage is variable within a given range depending on the associations (series/parallel) of the PV panels and the no-load voltage at every panel. The structure of the novel PV architecture is shown in

The DC/DC chopper (η3), commonly a buck one, controls the DC voltage levels feeding the loads. The DC /DC chopper (η1) is a reversible step-up-down one. This dc/dc chopper enables energy to be transmitted from the PV panels to the converter (η2) once the used energy by the load is much less than the electricity generated by the PV. Inversely, when the power absorbed by the load exceeds the one generated through the PV, this reversible DC chopper serves as a buck circuit and transmits power from the inverter (η2) which is drawn from the grid.

System 2 and system 3 use an identical number of converters. The benefit of the novel LVDC nanogrid is that the distance taken by the current from the PV terminals to the DC appliances is smaller during day hours corresponding to PV power availability. Nevertheless, in the absence of PV energy, the electrical way from the grid to the appliances will become higher. To assess the studied PV systems performances, computations are carried out during a representative day (24 h/day) in every season. Subsequently, economized energy is assessed for a complete year (365 days).

The transistors used in the different converters are the N-channel Insulated-Gate Bipolar Transistor IKW30N60T including antiparallel diodes from Infineon [

The corresponding circuit of the diode behaviour model is presented in _{1,} and a current source in parallel [_{1}:

The parameters a, b, and c are fitting parameters used to adjust different parts of the forward characteristics of the diode.

The simulated circuit of the IGBT behavior is presented in _{2} and R_{3}. These resistances adjust specific electrical characteristics, and the capacitances C_{2}, C_{3,} and C_{4} are voltage-dependent. The method used to implement the behavioral model is defined as a series connection of a capacitor C_{0} scaled by a controlled voltage source V_{0}; as an example of C_{4}, the voltage dependence of V_{0} is defined by the following equation:

The inductance L_{1} and L_{2} are parasitic inductances due to the semiconductors bonding, and the resistor R_{4} is the internal gate resistance [

The I(V) characteristics of the transistor and the diode obtained by simulation and datasheet [

The switching losses of the transistor/diode elementary cell are shown in _{st}) are the total switching losses when the controlled power device is switched on and off. The efficiency of the different converters determined by simulations according to the transmitted power is shown in

The equivalent circuit of the PV panel used to compute the novel LVDC architecture (system 3) consists of a generator of current with a parallel resistor, a series resistor as given in

where,

I_{L} is the sunlight current (A). I_{o} is the diode inverse saturation current (A). Q_{d} is the diode ideality factor, n_{s} is the number of cells in series. V_{d} is the voltage at the diode terminals. V_{T} is the thermal voltage (V).

The values of the PV panel equivalent circuit devices are provided in ^{2} and 600 W/m^{2} are given in (

Parameter | Value | Unit |
---|---|---|

Cells per module | 60 | – |

Light-generated current I_{L} |
9.3253 | A |

Diode saturation current I_{o} |
38.629 | pA |

Diode ideality factor | 0.95043 | – |

Shunt resistance R_{sh} |
588.1408 | Ω |

Series resistance R_{s} |
0.37955 | Ω |

V_{T} @ T_{c} = 25°C |
0.0257 | V |

The entire circuit of the new LVDC architecture (system 3) is presented in

The Perturb and Observe (P&O) MPPT technique is applied for the modeled 2 kW PV system to detect the point of optimum power. The diagram of the P&O technique is presented in

The simulation of the new LVDC PV architecture is conducted in two distinct situations. The first one is when the power generated by the PV panels (2.1 kW) is larger than the appliance’s absorbed power (0.94 kW). In this case, the PV’s surplus power is transferred to the grid

Jeddah location in Saudi Arabia (21° 32′ 34 ″N, 39° 10′ 22 ″E) was chosen to investigate the energy performance of the different PV architectures. According to the Koppen climate categorization, Jeddah has a dry climate with tropic weather. In addition, Jeddah has a pleasant winter climate with temperatures varying from 15°C (59 F) to 28°C (82 F) in the afternoon. Temperatures in summer, however, are particularly large in the afternoon, often surpassing 48°C (118 F), while dropping to 35°C (95 F) after sunset.

Annual interchanged energy between every PV system and the AC utility is referred to as W_{j} (j = 1,2 or 3). This is the surplus energy that is fed into the AC network once the household power demand has been met. The energy W_{j} is the integral of the balanced power P_{j} swapped with the AC utility by the systems (j). For each studied PV architecture, the power P_{j} is determined by the next expressions:

For usual LVAC (system 1):

where,

η_{1} and η_{2} are the efficiencies of the boost converter and inverter respectively.

P_{pv} and P_{load} are the generated power from PV and consumed by load respectively.

For conventional LVDC (system 2):

where,

For the new LVDC (system 3):

where,

The DC/DC chopper (η_{3}) is the same for the 3 studied converters and placed simply before the load, and its effect is no longer taken into consideration in the study.

Ammous et al. in [_{PV} produced annually.

W_{j} and W_{1} are obtained by the time integral of the exchanged power between the grid and the PV chain.

If the specified RSE is negative, the traditional LVAC grid-tie PV system (system 1) with AC appliances is more interesting (relating to power savings) than the LVDC supplies. On the other hand, if the variable RSE is positive, the LVDC structure is considered extra effective than the LVAC architecture.

We will examine the efficiency of the three structures for household loads. Three household demand profiles are taken into consideration. The household load consists of a garment dryer, a computer laptop, a dishwasher, a laser printer, a lamp, a microwave oven, a fridge, a tv liquid crystal display, a washing machine and an air conditioner [

The monthly RSE for each LVDC supply is presented in

The curves showing the RSE’s of the two LVDC supplies according to

The recorded LVDC chains RSEs for the first household are not enough significant. These weak performances are due to the fact that the home load demand within day hours is not important and the main of the PV produced power is fed into the AC utility. The household power consumption at night significantly lowers the efficiency of the LVDC architectures. Consequently, we deduce that the use of system 3 is unattractive for homes low self-consumption within daytime hours. The usual LVDC (system 2) is more attractive and records a higher efficiency increase of 2.4% compared to the classic LVAC system 1.

The annual RSE value for the new LVDC system 3 is now more important as depicted in

_{PV} is close (1.5 W_{Load}).

^{2} and 25°C for Jeddah location).

The Relative Saved Energy of the new LVDC supply (system 3) is more important than the ones registered in the last two cases. The RSE in each month exceeds 18% when the household energy consumption is low, as presented in

_{PV} ≈ 0.9 W_{Load} for the proposed LVDC architecture. For system 2 it is 15% considering a small home consumed energy.

The investigations conducted in the third case demonstrates and consolidates the fact that the use of LVDC supplies including solar PVs is more advantageous when the load consumptions occur within day hours and when it is close to the energy generated by the PV panels. With the new LVDC supply, the efficiency has been significantly improved in comparison with the usual LVDC supply. This increase is registered through a certain range of

In this paper, a more efficient structure of an LVDC supply idea is suggested. The new grid-tie PV architecture destinated for DC household uses allows to replace the classical on-grid PV chains using AC outlets to fed AC equipment. The performance evaluation of the proposed PV structures became possible by using accurate models of an IGBT and diode from Infineon. The proposed devices behavioural models give rapid calculation times and the precision is good enough. In addition, the concept of relative energy saving notion was proposed to confront the efficiencies rates of LVDC supplies for DC loads with classic PV chains feeding AC loads. The monthly and annual relative energy savings are presented in different residences under climatic conditions of the Jeddah site. The effects of solar radiation, ambient temperature and wind speed are considered for this location. Three houses demand profiles are considered to analyze the three investigated PV architectures. The registered results show that LVDC supplies concepts are more efficient than usual LVAC architectures, especially when the electricity is used on-site during day hours. Nevertheless, the performances of LVDC supplies repose mainly on

The authors would like to thank the Deanship of Scientific Research at Umm Al-Qura University for supporting this work by Grant Code: (22UQU4340526DSR01).