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This paper presents a fully distributed algorithm for the stochastic Volt/VAr control (VVC) problem in active distribution networks. Exact convexification of the VVC problem is achieved through the use of second-order cones on the continuous relaxation of the original optimization structure. The global optimum solution of the relaxed problem is obtained through the application of the alternating direction method of multipliers (ADMM). In order to minimize the effect of rounding off on the final solution, an adaptive threshold discretization technique is used. A two-stage control strategy is adopted where the discrete controllers, like load tap changers and switched capacitors, are dispatched at the beginning of the optimization interval and the continuous controllers, like distributed generation (DG) inverters, are adjusted in real time according to an optimized decision rule. The superiority of the proposed algorithm is demonstrated through numerical simulations on the UKGDS-95 and the IEEE-123 bus systems.

With the fast expansion of the power grid and increasing complexity due to modern equipment, power flow models with non-convexity and long computing time are not suitable for network calculation and optimization problems. Therefore, this paper proposes a linearized branch flow model (LBF) considering line shunts (LBFS). The strength of LBF lies in its linear mathematical structure, and hence the convex nature, which is primarily achieved by regarding the apparent power flow as the branch current magnitude. Moreover, the calculation accuracy in nodal voltage magnitude is significantly improved by appropriately modeling line shunt admittances and network equipment like transformers, shunt capacitors and distributed generators (DG). We show the application scope of LBFS by controlling the network voltages through a two-stage stochastic optimization Volt/VAr control (VVC) problem considering DG output uncertainty. Since LBFS results in a linear VVC program, the global solution is guaranteed. Simulations show that VVC framework can optimally dispatch the discrete control devices, viz. substation transformers and shunt capacitors, and also optimize the decision rules for real time reactive power control of DGs. Besides, the computing efficiency is significantly improved compared to traditional VVC methods.

This paper presents a two-stage three-phase solar photovoltaic (PV) system, which is controlled through a novel enhanced second order generalized integrator (ESOGI) based control technique. The proposed ESOGI is used for fundamental component extraction from nonlinear load current and distorted grid voltages. This integrator effectively and simultaneously manages to address the DC offset, inter-harmonic and integrator delay problems of the traditional SOGI. In addition, this control technique provides power factor correction, harmonic elimination, and load balancing functionalities. The ESOGI controller is used to generate reference grid currents for controlling the voltage source converter (VSC), interfacing the PV panel with the grid. Extensive simulation and experimental results on a developed prototype in the laboratory, depict that the total harmonic distortion (THD) of the grid injected currents and voltages are found well under IEEE-519 standard.Index Terms-Solar photovoltaic (PV) system, maximum power point tracking (MPPT), second order generalized integrator (SOGI), power quality.