0000000000918279
AUTHOR
A. Augugliaro
Simple measures to improve the performances of the backward/forward method for radial distribution network analysis
In the paper, after having presented the general backward/forward methodology for radial systems analysis, the main changes that have been proposed in the past to improve their convergence and speed performance are shown. Some measures aimed at a further reduction of the number of iterations and calculation times are here described. In order to identify, among the available alternatives, the best methodology, in terms of precision and/or speed of convergence, some evaluations on networks taken from the literature have been carried out. The analysis of the attained results allows the definition, on the basis of specific features of the problem at hand, the most suitable configuration to be i…
A Backward Method for Solving PV Nodes in Weakly Meshed Distribution Networks
In this paper, a new iterative backward/forward methodology for the load flow solution of weakly meshed systems with fixed voltage nodes is presented. Such technique models the loads at each iteration by means of impedances, and the PV nodes by means of reactances. Each iteration is organised in two steps. In the first, the radial network attained from the meshed system through cuts and composed of shunt and series impedances is solved. In the second step, based on a reduced Thévenin impedance matrix, the compensation currents to be injected in the cut nodes are deduced. Modelling the PV nodes by means of reactances allows the attainment, for the reactive power of these nodes, of the same p…
Load flow analysis of radial distribution networks: New findings in backward/forward method
In the paper, the backward/forward method for solving radial distribution networks is in details described. In particular it is examined considering the four main steps into which it can be divided: initialization of the state variables; backward sweep; forward sweep; identification of a convergence criterion. For each of these, except for the forward sweep, a new procedure is defined. In particular, a methodology for the identification of a starting solution that is as close as possible to the desired one is proposed; the backward phase is modified for the evaluation of the branch currents and a new convergence criterion is proposed. The results of the application of the proposed methodolo…
An analytical model for PQ sources in backward/forward methods for distribution networks analysis
In this paper a model of PQ sources useful for distribution systems analysis is developed. In the considered systems there are, in addition to HV/MV sources, other PQ buses, namely active and reactive power supply nodes (Vδ nodes). The general solution strategy is an iterative forward/backward method, in which the state variables are the node voltages. If it is weakly meshed, the network is turned into radial by means of cuts and compensation currents. After the presentation of the general problem, the equations expressing the unknowns for the PQ nodes are treated in detail. These equations belong to the backward sweep of the algorithm. The methodology has been implemented and applied so as…
A decoupled method for solving distribution networks with PV nodes
In this paper, a methodology for the load flow solution of distribution systems with fixed voltage nodes (PV nodes) is presented. The proposed technique is the extension of a methodology already set up by the authors to solve distribution systems; it is an iterative approach devoted to the treatment of voltage dependent loads; at each iteration, all the network components (lines, loads, and PV nodes) are represented by resistances and reactances. The methodology is based on the identification of two networks that are solved in sequence, thus allowing the attainment of state features of the original system. One of the two systems is made up only of shunt and series resistances; the other onl…
Voltage Collapse Proximity Assessment for Radial Distribution Networks
The paper deals with voltage stability assessment in radial distribution networks. The voltage collapse proximity index already utilized in literature for power transmission systems is assumed. Based on the optimal impedance solution of a two-bus equivalent system, this index indicates how far the load nodes of the actual network are from their voltage collapse points, allowing the weak node and its maximum load power beyond which voltage collapse takes place to be identified. The proposed method differs from the other methods on the determination of the parameters which define the two-bus equivalent of the network, allowing to better identify the maximum loading point beyond which the volt…
Optimal reconfiguration of weakly meshed distribution systems
In this paper the problem of optimal reconfiguration for weakly meshed systems is dealt with; meshes are created by the presence of Favoured Customers (FC) requiring supply through two different paths in order to guarantee the maximum service continuity. Aim of the reconfiguration is to attain a network that operates with minimum power losses, and in order to account for particular needs of the FC loads, that shows the minimum overall yearly fault rate on the branches where the power required by the loads flows. Moreover the constraints concerning the bus voltage profiles, the current in branches and the power balance among HV/MV transformers supplying the network must be full-filled. Due t…
Direct solution of compensated radial distribution networks with constant impedance/current loads
In this paper, a methodology to solve radial distribution networks, with constant current and/or impedance loads as well as shunt capacitor banks, is proposed. The techniques currently available to solve such systems are based either on iterative methods or on the bus impedance matrix. In both cases, the elaboration times are quite high since these are related, for iterative methods, to the overall number of iterations, and, for those methods based on the impedance matrix, to the inversion of the admittance matrix. The method developed here is the extension of a technique that is valid to solve networks made of impedances with one supply point. The methodology can also be applied in the sol…
A new model of PV nodes in distribution networks backward/forward analysis
In this paper a new model of PV nodes is developed; the model is aimed for the distribution systems load flow analysis and, in particular, for the iterative forward/backward method. If the network is weakly meshed, it is turned into radial by means of cuts and compensation currents. After the presentation of the general problem and the state of the art on the subject, the equations expressing the unknowns for the PV nodes are treated in detail. These equations belong to the forward sweep of the algorithm. The methodology has been implemented and applied so as to test its performance in terms of calculation times and precision. The obtained results confirm the efficiency of the proposed appr…