C I R E D 18 th International Conference on Electricity Distribution Turin, 6-9 June 2005 OPTIMAL LOCALIZATION OF VOLTAGE REGULATOR BANKS IN DISTRIBUTION SYSTEMS BASED ON TECHNICAL AND ECONOMIC CRITERIA Angelo M.F. ALMEIDA, Benemar A. SOUZA, Franklin M. P. PAMPLONA, Helon D. M. BRAZ Federal University of Campina Grande — BRAZIL {angelo, benemar, franklin, helon}@dee.ufcg.edu.br INTRODUCTION The optimal control of voltage profile with mono-phase voltage regulators banks in radial distribution feeders is presented. The formulation is made as a combinatorial optimization problem and solved by a Genetic Algorithm. The used optimization criteria are: voltage profile centred in the normal range, losses and costs reductions. The proposed method determine: the location and optimal adjustments of mono-phase regulator banks in maximum and minimum load conditions, and the maximum regulation. THE CONTROL OF VOLTAGE PROFILE The control of voltage profile and reduction of losses in radial distribution feeders usually has been treated with installation of capacitor banks and voltage regulators by electric power utilities. Voltage regulators are mainly applied in extensive and loaded feeders, where the reactive compensation does not have satisfactory effect. These are low cost solution in comparing to others which are demanded whether the problems of that nature are too intense, such as: conductors resizing, network reconfiguration, implantation of new feeders, construction or amplification of substations. In [1], is presented the application of voltage regulators with the integrated control of voltage and reactive power (volt/var), where are shown: the modelling of the components of the system, the analytic treatment of the objective functions and an example of application. However, one does not consider the discrete characteristic of problem, since the installation buses of the banks and the taps that the same ones should operate form a discrete and finite group. The modelling and implementation of the integrated control are presented in [2,3] too. However, they use the Gauss-Sidel load flow method with uniform distribution of load, having limitations for networks highly loaded. In [4] an algorithm was proposed for location of voltage regulators in distribution systems that takes also into account the costs, but looks for solutions for approaches of the voltage profile, in relation to the profile without regulator, in agreement with the used tap and tries to elevate the voltage the possible maximum. The volt/var integrated control is also done in [5], being that costs and typical load curves are considered. In [6,7] a genetic algorithm is presented for optimal location of regulators in radial distribution systems, taking into consideration the search space as a discrete and finite group. The first one uses three-phase regulators, the other using mono-phase regulator banks. The work presented here is a continuation of [7]. Now for location and optimal adjustments of mono-phase regulator banks, one takes into account the reduction of the energy losses costs originated from the installation of the banks, considering a typical load increasing of medium term, and using a genetic algorithm with reduced search space. ADOPTED MODELS Radial Feeder and Type of Load As usual for radial distribution feeders, has been adopted a simplified model of the line with just impedance series. The load model of constant power, predominant in urban feeders [8], was used. Voltage Regulator and Mono-phase Regulator Bank The automatic voltage regulator is an autotransformer with load derivation changer, an electromechanical device controlled by voltage relay. The mono-phase regulator bank is the most usual configuration in three-phase distribution systems. In the closed delta configuration (Fig. 1) the regulation band is 50% larger. That means if the mono-phase units have regulation range of ±10% each, then, the effective regulation of the bank is ±15%. Another advantage is that if one of the mono-phase regulator flaws, the other two can stay in operation, in the configuration delta-opened, maintaining the voltage levels still regulated and the load capacity assisted by the bank. In that case, the regulation will be limited to ±10%. V ab V bc V ca V la V lb V lc I la I lb I lc Fig. 1 - Bank of mono-phase regulators linked in closed delta. The equations (1) – (3) relate the output voltage magnitude (V) and angle displacement (∆) of the mono-phase regulator bank linked in closed delta, with the input voltage magnitude (v) and used step, d. CIRED2005 Session No 5