Abstract
This paper proposes a novel optimization method, namely, hybrid PSOS-CGSA for state estimation in three-phase unbalanced DG-integrated distribution systems. The distribution system state estimation (DSSE) is formulated as a nonlinear optimization problem with constraints where loads and DG outputs are considered as the control variables, while real-time measurements are treated as dependent variables. The proposed DSSE model estimates the loads and DG outputs at each bus by minimizing the difference between the measure and calculated values of the variables monitored in real-time. A novel hybrid algorithm of particle swarm optimization with sigmoid-based acceleration coefficients and chaotic gravitational search algorithm (PSOS-CGSA) is proposed and applied for the DG-integrated DSSE. The feasibility of the proposed approach is verified on the IEEE 13-bus test system, the IEEE 37-bus test system, and the IEEE 123-bus test system. These simulations show that the proposed DSSE model provides reliable and accurate state estimation of DG-integrated distribution systems with a very limited number of real-time measurements at the source substation. The results obtained by proposed hybrid PSOS-CGSA are evaluated by comparing with other methods under the same test conditions, and the obtained results demonstrate the merits of the proposed scheme.
Highlights
CONTRIBUTION AND PAPER ORGANIZATION This paper proposes a new three-phase distribution system state estimation (DSSE) paradigm based on metaheuristic optimization
In case the distributed generation (DG) units modeled as PV buses, the power flow algorithm requires some additional processes related to calculating the reactive power injections at the PV buses needed to achieve the specified voltage magnitudes [18]
Significant improvements of the DSSE results can be achieved with additional real-time measurements in the lateral branches
Summary
In paper [5], Ranković et al proposed an improved WLS based three-phase SE algorithm for unbalanced distribution systems, where the vector of state variables comprises the components of complex voltages combined with variables associated with the classification of integrated DG units. Othman et al proposed a DSSE model considering DG integration in distribution networks [10] This technique is based on updating the complex power flow in the overall network according to the online measurement from smart meters positioned at specific locations dependent on the network topology only. B. TRANSFORMER MODELLING The first problem in applying the backward/forward sweep-based power flow method for the unbalanced radial distribution networks with multiple voltage levels is reflected in the inability of direct summarizing branch currents (backward sweep) and calculating the bus voltages (forward sweep) for three-phase transformer whose secondary windings connections are delta or ungrounded wye. In case the DG units modeled as PV buses, the power flow algorithm requires some additional processes related to calculating the reactive power injections at the PV buses needed to achieve the specified voltage magnitudes [18]
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