Vannak Vai

Planning of low voltage distribution system with integration of PV sources and storage means : case of power system of Cambodia: La consommation d'énergie augmente d'année en année en raison de la croissance de la population et des conditions économiques. Afin de répondre aux besoins de la population et de la société d'utiliser l'électricité, le Gouvernement Cambodgien a mis en place la politique de promotion et d'encouragement du développement de l’électrification ; tous les villages auront de l'électricité d'ici 2020 et au moins 70% des domiciles auront accès à la bonne qualité du réseau électrique d'ici 2030. Pour réussir ces objectifs, l'étude et le développement de la méthodologie du réseau de distribution basse tension (BT) sont étudiés. Cette thèse étudie la planification du réseau de distribution BT avec intégration de Photovoltaïque (PV) et de stockage d’énergie de batterie (BES). La première partie est développée la méthode de planification à long terme pour tacler le défi de l'incertitude sur la charge en zone urbaine ;le nouvel algorithme a été développé pour rechercher l'architecture optimale de minimisation du coût d’investissement (CAPEX) et d’exploitation (OPEX) qui respecte l'ensemble de contraintes topologies et électriques (courant et tension) grâce à la programmation linéaire mixte en nombres entiers à contraintes quadratiques (PLMNECQ), le plus court chemin , first-fit bin-packing, et la méthode de Monte-Carlo. La deuxième partie est traité de l'extension de la zone de couverture de l'électricité avec deux solutions possibles, sont le renforcement du réseau et l'intégration de PV-BES pour le village rural ; l'algorithme génétique (GA) et la technique itérative ont été codés pour rechercher l’emplacement et la capacité. La dernière partie du travail est concentrée sur la planification du réseau de distribution résidentielle BT pour les zones non électrifiées aux rural et urbain grâce à l'architecture optimale et l'intégration de PV-BES sur l'horizon de planification.

This paper aims to define the optimal microgrid topology for rural electrification based on the lowest total cost by comparing LVAC and LVDC microgrids across three different scenarios. An LVAC radial topology is first designed using mixed-integer linear programming for phase balancing and the shortest path for connections, then implemented with a genetic algorithm to allocate and size solar home systems, forming an LVAC microgrid. Next, an LVDC topology is then derived from the LVAC structure and integrated with solar home systems under three scenarios: (1) using the same solar home system sizes, locations, and quantities as the LVAC microgrid; (2) using a genetic algorithm to re-determine solar home system sizes and locations, forming an LVDC microgrid; and (3) clustering the LVDC topology into nano-grids, each defined by genetic algorithm for solar home system sizing and placement and connected to the main feeder via bi-directional converters. Finally, all LVAC and LVDC scenarios are simulated over a 30-year planning horizon for analysis. A non-electrified village located in Cambodia has been selected for a case study to validate the proposed methods. The results have been obtained and provide a comparison of performance indicators (i.e., costs, energy production, losses, CO₂ emissions, and autonomous energy) among the microgrids (LVAC and LVDC). The LVAC microgrid produced lower total energy losses than the LVDC microgrid in all scenarios. However, when considering environmental impact, LVDC Scenario 2 is preferable. Based on the total cost results, the LVAC microgrid is considered more economical than the LVDC microgrid in each scenario in this study.

This paper aims to define the optimal microgrid topology for rural electrification based on the lowest total cost (TOTEX) by comparing LVAC and LVDC microgrids across three different scenarios. An LVAC radial topology is first designed using MILP for phase balancing and SP for connections, then implemented with a GA to allocate and size SHSs, forming an LVAC microgrid. Next, an LVDC topology is then derived from the LVAC structure and integrated with SHSs under three scenarios: (1) using the same SHS sizes, locations, and quantities as the LVAC microgrid; (2) using GA to re-determine SHS sizes and locations, forming an LVDC microgrid; and (3) clustering the LVDC topology into nano-grids, each defined by GA for SHS sizing and placement and connected to the main feeder via bi-directional converters. Finally, all LVAC and LVDC scenarios are simulated over a 30-year planning horizon for analysis. A non-electrified village located in Cambodia has been selected for a case study to validate the proposed methods. The results have been obtained and provide a comparison of performance indicators (i.e., costs, energy production, losses, CO₂ emissions, and autonomous energy) among the microgrids (LVAC and LVDC). Based on the TOTEX results, the LVAC microgrid is considered more economical than the LVDC microgrid in each scenario in this study.

This paper aims to minimize the distance of the feeder path from high-voltage/medium-voltage (HV/MV) substation to medium-voltage/low-voltage (MV/LV) transformers and minimize power loss in an unbalanced distribution system by the phase-swapping concept-based load balancing. The shortest path algorithm (SPA) and the genetic algorithm (GA) for optimal feeder routing and phase balancing separately in the MV unbalanced distribution network are proposed. First, the relevant data for the system is collected. These data include substation coordinates (X, Y), active and reactive power (P, Q), phase connections, and lines’ impedance (Z). secondly, the performance of the existing configuration of the test system with numerous indications is presented. Finally, the proposed method is performed to minimize the length and power losses. The real 47-bus test system in Cambodia is chosen to demonstrate the proposed method. In this study, overall power losses, the maximum voltage imbalance, and voltage regulation are computed by the backward/forward sweep load flow. The results based on the simulation indicate the importance of the proposed approach, especially for distribution system designers and operators.

Energy demand is continuously increasing, leading to yearly expansions in low-voltage (LV) distribution systems integrated with PVs to deliver electricity to users with techno-economic considerations. This study proposes and compares different topology planning strategies with and without PVs in a rural area of Cambodia over 30 years of planning. Firstly, the optimal radial topology from a distribution transformer to end-users is provided using the shortest path algorithm. Secondly, two different phase balancing concepts (i.e., pole balancing and load balancing) with different phase connection methods (i.e., power losses and energy losses) are proposed and compared to find the optimal topology. Then, the integration of centralized (CePV) and decentralized PV (DePV) into the optimal topology is investigated for three different scenarios, which are zero-injection (MV and LV levels), no sell-back price, and a sell-back price. Next, the minimum sell-back price from CePV and DePV integration is determined. To optimize phase balancing, including the location and size of PV, an optimization technique using a water cycle algorithm (WCA) is applied. Finally, an economic analysis of each scenario based on the highest net present cost (NPC), including capital expenditure (CAPEX) and operational expenditure (OPEX) over the planning period, is evaluated. In addition, technical indicators, such as autonomous time and energy, and environmental indicator, which is quantified by CO₂ emissions, are taken into account. Simulation results validate the effectiveness of the proposed method.

Recently, DC-powered devices such as loads (USB plugs, chargers, LED lighting) and distributed energy resources (solar photovoltaic and battery energy storage) have been increasingly used. Therefore, their connection to the grid requires AC/DC converters, which raises the question of operating part of the grid in DC in order to connect DC loads to DC producers and storage. In Cambodia, the electrification rate is only about 82% of the population in 2021 in rural areas. The objective of this work is to propose a low voltage microgrid comprehensive planning tool for electrification of developing countries. From the data collected on consumption needs, the objective is to find the optimal electrification scheme, i.e., AC or AC/DC distribution, optimal topology and distributed energy resources allocation and operation for both grid-connected and off-grid mode. A set of technical, economic, and environmental key performance indicators allows for comparison of solutions. The interest and efficiency of such a tool are illustrated on a real case study, an island area. Moreover, uncertainties on load consumption are also considered to assess the sensitivity and robustness of the proposed algorithm. The results show that, although the overall cost of the hybrid AC/DC microgrid is slightly higher than that of the AC microgrid, it allows a gradual electrification avoiding large initial investments.

This paper addresses the planning of low-voltage microgrid by comparing its structure with and without PV and storage in a rural area for over 30 years. The comparison aims to minimize the investment costs and get a reliable system. First, the loads (households) have been surveyed in the targeted areas and their power consumptions estimated. Then, using the Shortest Path (SP) algorithm, the connections from loads to electrical poles are conceived for the whole network. Next, the Mixed Integer Linear Programming (MILP) algorithm has been considered to balance the three-phase system. After that, the Genetic Algorithm (GA) is employed to determine the location and sizing of PV and decentralized batteries. A centralized battery is set to store the reversed power from the network to the grid and provide the power back when the PV modules produce less energy. Finally, an economic analysis validates the interest of such planning procedure. Located in Cambodia, three cases studies are implemented into the proposed method to get the results. Based on the results from simulation, the systems with integrated PV and storage proves to have a better performance.

The paper focuses on designing low voltage (LV) distribution network topologies with PV integration with load profile uncertainty considering the minimum power loss, balanced load, and cost of energy. In the first step, the repeated phase ABC algorithm is created to search for a balanced load from the MV/LV transformer to all households. Next, the genetic algorithm (GA) is implemented to find out the optimal topology with minimum power loss as the second algorithm. Then, the load profile impact on network topologies is investigated. A comparative study of two different concepts allows providing that the genetic algorithm is the optimal solution in designing the LV distribution network topology. Finally, the economic analysis of the grid-connected PV system with different electricity tariffs with hybrid optimization software is provided over the planning study. To confirm the proposed method, a distribution network of 45-buses in the urban area in Phnom Penh city, Cambodia, is chosen for a studied case.

The low voltage (LV) distribution systems are extended year by year due to the increase in energy demand. To overcome this issue, distribution system utilities have been focusing on designing and operating an appropriate distribution system with minimum capital and operational expenditure for supplying electricity to users. This article compares different algorithms to design an LVAC distribution system in a rural area, which focuses on minimizing the total length of lines and the power losses and balancing the loads among the three phases including the economic evaluation of the grid-connected PV system. Firstly, the shortest path (SP) algorithm is established to search for the minimization of the conductor used. Secondly, three different algorithms which are repeated phase sequence (RPABC), first fit bin packing (FFBP), and mixed-integer quadratic programming (MIQP) algorithms are developed to balance the load and minimize power losses. Next, a comparative result of three different algorithms is provided. Finally, the techno-economic analysis of the grid-connected PV system with different electricity tariffs with hybrid optimization of multiple energy resources (HOMER) software is studied in the planning period. To validate a proposed method, the 129-buses low voltage distribution in a rural village, in Cambodia, is tested. The simulation result confirms the optimal solution of the MIQP algorithm and PV system integration in designing a distribution system in a particular case study.