In English

Optimal placement of reactive power supports for loss minimization: the case of a Georgian regional power grid

Otar Gavasheli
Göteborg : Chalmers tekniska högskola, 2007. 66 s.
[Examensarbete på avancerad nivå]

Power system operators/planners are always faced with the problem of how to minimize the transmission loss. There are a number of ways to achieve this goal. In this thesis, new methods for optimal capacitor placement for transmission loss minimization are proposed. Proposed methods are based on the optimal power flow formulations, which enable the costbenefit analysis and multi-objective optimization assessment of reactive power support investment. For better illustration of proposed methods, they are applied to a real and test transmission networks. In the cost-benefit analysis, reactive power supports are applied to the power system for transmission loss minimization. The candidate places for reactive power support allocation are defined in advance according to where the highest reactive power flow is observed. The benefits after application of reactive power supports are calculated. Benefits considered are the benefits from recovered transmission losses due to the reactive power addition. The benefits are then compared with investments, which would be required for the addition of reactive power supports and in this way the economical justification in reactive power support addition can be made. This method is applied to the real transmission network of a Georgian regional grid. After analyzing the obtained results, we can observe that in some cases even though the losses are minimized up to the minimal level, economically it is not optimal since in such cases, high investment costs are involved. The optimal cases are those where the losses are a bit higher than possible minimum and the investments are minimal also compared to what is required for achieving of minimal transmission losses. Only these optimal cases can justify the investments, made for loss minimization. In the multi-objective optimization several objective functions are proposed in one overall objective function. The optimized functions are minimization of total investment in reactive power support, average voltage deviation, minimization of total system loss and total system cost. At the beginning, optimum values for each objective function is found one by one separately and these optimal values are included while solving for overall objective function. During optimization of all these objectives within one overall objective, we have opportunity to optimize each objective according to what is our interest in it compared to other optimized objectives. This is done using the priority order multipliers, which has each of the objective functions. CIGRE 32 bus test system is used for illustration of this method. Three cases with different values of priority order multipliers are solved and discussed. In the obtained results we can observe how the values of optimized objective functions are changed to reflect their priority orders assigned in the overall objective function.

Nyckelord: Loss minimization, reactive power support, optimal power flow, costbenefit analysis, multi-objective optimization

Publikationen registrerades 2013-02-27. Den ändrades senast 2013-04-04

CPL ID: 174186

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