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Planning of low voltage distribution system with integration of PV sources and storage means: Case of power system of Cambodia
Abstract
The energy consumption increases year by year due to the growth of the population and theeconomic conditions. In this context, the Cambodian government promotes and encourages thedevelopment of the electrification through several policies; all the villages must be electrified by2020 and at least 70 % of the households will be connected to the network by 2030. Besides, lotsof non-electrified homes are equipped with solar panels so as to have access to the electricity. Then,the objective of this thesis is to develop planning tools of the low voltage distribution network tocontribute to the electrification of the country. The first part of this thesis focusses on thedevelopment of architecture’s optimization methods to minimize the capital expenditure (CAPEX)and operational expenditure (OPEX) while respecting both topological and electrical constraints(current and voltage) and integrating the uncertainties on the future development of the low voltagecustomers. The second part of the thesis proposes a new planning solution so as to integrate thecurrent and future solar productions on the low voltage network. This solution consists in addingcentralized storage (in urban and rural areas) and decentralized storage (in rural areas). The mainadvantages would be first to reduce the consumption peak of the medium voltage /low voltagetransformer and consequently to reduce the medium voltage investments but also to size low voltage"microgrids" which can be autonomous a big part of the year. A technical and economic comparisonwith the classic solution of reinforcement allows estimating the interest of this new solution.
... It can be noted that the previously listed criteria can sometimes be contradictory, since, for example, low carbon options often increase costs. The objective function of this planning problem can be expressed with Equation (1) subject to the constraints of Equations (2) and (3) [41]. , , , and defined below are normalized relative to target values defined by the user. ...
... It can be noted that the previously listed criteria can sometimes be contradictory, since, for example, low carbon options often increase costs. The objective function of this planning problem can be expressed with Equation (1) subject to the constraints of Equations (2) and (3) [41]. C Total , C CO 2 , C auto time , and C auto energy defined below are normalized relative to target values defined by the user. ...
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.
... In rural areas, the authors [8] focused on the use of a single-phase distribution network instead of both three-phase and single-phase by using the shortest path concept. The shortest path concept is also implemented in [9] to extend a single-phase distribution system for a non-electrified village in a rural area. However, it can be noticed that these works had almost focused on length minimizing and load balancing improvement without minimum power loss as the operation investment for both urban and rural villages with a single-phase distribution network. ...
... Since currently there is no available information, the normalized curve is generalized to simulate a year. The detailed information of the case study is provided in [9]. The setup of load profile measurement and normalized load curve for simulation are provided in Figure 5a,b. ...
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.
... Moreover, the maximum power output (P max ), the active power (S) and reactive power values (Q) of PV inverters were controlled and calculated appropriately and A nonlinear of the requiring reactive power focused on against the fluctuations of the active power output with a different value of voltage variation margin. The PCC communication of a weak grid-tied PV inverter as depicted in Figure 2 and the specification of the voltage fluctuation value (ΔV) is utilized as the common formula [18], [22]. There are two core indicators reflect the foundation of the grid strength at PCC, that is, the short circuit ratio (SCR) or the inductive-resistive ratio (IRR) of the weak grid system defined by the mathematical equation and when the grid is considered weak if IRR is smaller than 0 . ...
... The distribution system is used to transfer electrical power to users from the high voltage (HM)/Medium voltage (MV) and the MV/Low voltage (LV) system. In addition, the voltage standard is applied in Cambodia as demonstrated in Table 2 [22]. ...
span lang="EN-US">A single-phase grid-connected PV inverter performance under a weak grid is a model designed to penetrate PV energy with a weak grid. Usually, this model gets complex and unstable in power system control such as THD growth, harmonic effects, voltage surges, inverter performance. Experimental results would present the impacts on the system which would lead to instability in the grid system. This study was based on inverter performance control, a weak grid control, the grid distortion examination, and harmonic effects. To optimize this grid system, hence, the proposed methods of oscilloscope and power meter were proportionally used to control the grid impacts and stabilities. The results showed that current THD in distorted grid voltage system surged to 8.88%. V<sub>PCC</sub> growth was 238.11V, equivalent to 8.23% in a weak grid (X<sub>L</sub> and R). Such a huge increase could prevent the grid system from transferring power for later operation. During the experiment, the inverter, S power and Q power performances stood for good operating processes without impacts on the grid performance. This method should be applied with a weak grid system because it provided information about grid stability control.</span
Unbalanced operation of distribution systems deteriorates power quality and increases investment and operation costs. Feeder reconfiguration and phase swapping are the two main approaches for load balancing, being the former more difficult to execute due to the reduced number of sectionalizing switches available in most distribution systems. On the other hand, phase swapping constitutes a direct, effective and low cost alternative for load balancing. The main contribution of this paper is the proposal of an optimization model and a solution technique for phase balancing planning in distribution systems. As regards the optimization model, a mixed integer nonlinear programming formulation is proposed. On the other hand, the proposed solution technique consists on a specialized genetic algorithm. To show the effectiveness of the proposed approach, several tests are carried out with two distribution systems of 37 and 19 buses, this last one with different load models. Results showed that in addition to the achievement of the primary objective of loss reduction, phase balancing allows obtaining other technical benefits such as improvement of voltage profile and alleviation of congested lines.
In planning of radial power distribution system, optimal feeder routing play an important role. This paper proposes a simple approach to optimize the total annual cost of the network, which represents investment cost (fixed cost) for feeder line as well as substation and operational costs (energy loss costs). The main objective of this method is to find the optimal route for each load point in large size electric power distribution system and to obtain the optimal radial network. An algorithm is proposed for simplified case study of a feeder network. The proposed algorithm is validated using MATLAB and the result thus obtained is compared with the existing results. The numerical results with different test cases are discussed, thus verifying the effectiveness of this approach. Index Terms—Feeder routing, load flow analysis, path search algorithm, radial distribution network
Much of the research has been focused on developing the optimization techniques, varying from classical to nontradi-tional soft computing techniques, to solve the distribution system planning problem. Most of the methods preserve the distinctions and niceties, but dependent on complex search algorithm with a lot of convergence related issues that require more time to reach a firm conclusion at planning stage. This paper proposes a simple direct solution that significantly reduces the inherent difficulties of finding the solution and ensures optimum solution at the same time. Moreover, the concept of principle of optimality is effectively used to make the proposed technique more computationally effi-cient and useful. The effectiveness of the developed planning tech-nique has been verified with different test cases. Index Terms—Distribution system planning, direct solution ap-proach, principle of optimality, load flow analysis.
This research work presents a study of Low-Voltage (LV) distribution system integrated with Photovoltaic (PV) and Battery Energy Storage (BES) for an urban area in developing country. This work purposes to search an optimal topology and sizing of PV-BES for supplying the consumers. A mixed integer quadratically constrained programming (MIQCP) is developed at first to find out the optimal topology with minimization of conductor use and phase balancing improvement. Next, a maximum PV penetration is sized by using Genetic Algorithm (GA) and Fmincon solver. The sizing strategies are established to determine a BES capacity according to time-varying solar radiation and demand curves. The results obtained on an example of LV test system show the validity of novel algorithm for optimal topology, PV size and centralized BES capacity
In a long-term planning procedure of distribution networks, it is essential to design an appropriate topology in order to satisfy economic and technical aspects. This paper presents a novel algorithm to optimize the topology and phase balancing to tackle the challenge of load demand uncertainty (i.e., growth rate and new load). The paper aims at developing a longterm planning tool of low-voltage (LV) distribution systems to find which load connection phase induces the lowest costs (investment and power losses) and balancing system improvement while satisfying the constraints over the planning horizon. A mixed integer quadratically constrained programming (MIQCP)-arborescence flow and shortest path in parallel with first-fit bin packing are developed to realize this work. In this study, an example of LV distribution system with 33 buses is applied to be a case study of the initial planning year. To evaluate the results, Monte Carlo (MC) simulation method is employed to determine the statistical actualized costs of different strategies. The simulation results support the validity of the methodology proposed in this article.
Cette thèse porte sur l'étude des apports de la flexibilité dans les réseaux Smart Grids Basse Tension. Ces derniers étant fondamentalement différents des réseaux Moyennes et Hautes Tensions, la gestion des flexibilités BT ne peut être calquée sur celle des réseaux MT et HT. De nouveaux moyens de contrôle doivent donc être développés. L'apport de ces flexibilité est analysé selon deux principaux bénéfices: la gestion opérationnelle la réduction de la pointe. Le premier apport porte donc sur le maintien des variables critiques à l'interieur des contraintes admissibles. Le but est de pouvoir gérer le réseau au plus près de ses limites, et donc d'éviter d'avoir à le renouveler, nottament en cas d'insertion importante de production décentralisée ou de véhicules électriques. La flexibilité utilisée est la gestion coordonnée des production décentralisées (puissances actives, réactives et phase de connection) et d'un régleur en charge. Le second porte sur la réduction de la pointe de consommation, soit au niveau du transformateur, soit au niveau national. La flexibilité utilisée est le délestage du chauffage électrique pendant une courte durée, suivie d'un rebond de puissance lorsque le chauffage est rallumé.