Abstract
The penetration of inverter-based distributed generators (DGs), which can control their reactive power outputs, has increased for low-voltage (LV) systems. The power outputs of DGs affect the voltage and power flow of both LV and medium-voltage (MV) systems that are connected to the LV system. Therefore, the effects of DGs should be considered in the volt/var optimization (VVO) problem of LV and MV systems. However, it is inefficient to utilize a detailed LV system model in the VVO problem because the size of the VVO problem is increased owing to the detailed LV system models. Therefore, in order to formulate and solve the VVO problem in an efficient way, in this paper, a new equivalent model for an LV system including inverter-based DGs is proposed. The proposed model is developed based on an analytical approach rather than a heuristic-fitting one, and it therefore enables the VVO problem to be solved using a deterministic algorithm (e.g., interior point method). In addition, a method to utilize the proposed model for the VVO problem is presented. In the case study, the results verify that the computational burden to solve the VVO problem is significantly reduced without loss of accuracy by the proposed model.
Highlights
Owing to opposition to the installation of new transmission facilities and the environmental issues associated with large-scale nuclear and thermal plants, a distributed generator (DG) is emerging as an alternative power source in distribution systems
The second term corresponds to the variations that are due to the reactive power control of DGs, while the last one refers to the variation due to the voltage magnitude change of the MV bus
If another method is used to on-load tap changers (OLTCs) and the number of shunt capacitors), in this paper, the local search method proposed in [35] was solve the volt/var optimization (VVO) problem, the proposed model can be used by applying the parameter adopted, where the integer variables are relaxed to continuous variables and the two integer solutions determination process, i.e., Steps 1, 4, and 5, into the original method, which corresponds to Steps 2 closest theshown relaxed-integer and to
Summary
Owing to opposition to the installation of new transmission facilities and the environmental issues associated with large-scale nuclear and thermal plants, a distributed generator (DG) is emerging as an alternative power source in distribution systems. Various volt/var optimization (VVO) methods that consider DGs and that utilize DGs as a controllable resource have been proposed for medium-voltage (MV) distribution systems (e.g., 1 kV < VMV < 100 kV) [4,5,6,7]. A new analytical equivalent model for an LV system is proposed considering the effect of reactive power control of DGs on the network power losses and voltages. The proposed model can be utilized to realize VVO for both MV and LV systems considering the reactive power control of the DGs. the proposed model can be adopted to VVO using deterministic optimization methods, which are generally faster and more stable than heuristic methods [23], because it is an analytical model.
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