Optimal sizing and placement of distributed storage in low voltage networks

Abstract

Abstract-This paper proposes a novel algorithm to optimally size and place storage in low voltage (LV) networks based on a linearized multiperiod optimal power flow method which we call forward backward sweep optimal power flow (FBS-OPF). We show that this method has good convergence properties, its solution deviates slightly from the optimum and makes the storage sizing and placement problem tractable for longer investment horizons. We demonstrate the usefulness of our method by assessing the economic viability of distributed and centralized storage in LV grids with a high photovoltaic penetration (PV). As a main result, we quantify that for the CIGRE LV test grid distributed storage configurations are preferable, since they allow for less PV curtailment due to grid constraints.Keywords-multiperiod optimal power flow, linear power flow approximation, optimal battery sizing and placement

A Centralised Control Method for Tackling Unbalances in Active Distribution Grids

“…These can be classified as centralised approaches based on Optimal Power Flow (OPF) [1]- [4], distributed [5], or local [6], each requiring different levels of communication infrastructure. Typical objectives used in these methods include minimizing active power curtailment of renewables [3] and network losses [2], while satisfying power quality constraints in terms of voltages limits and thermal loading of the branches.…”

“…First, we present a centralised controller based on a multi-period OPF formulation that extends the work in [1]- [3] to optimise the operation of three-phase unbalanced DNs. We extend the OPF formulation to three-phase systems and include additional power quality (phase balancing) constraints to the original formulation.…”

“…CENTRALISED OPF-BASED CONTROL SCHEME Centralised control of distribution networks based on OPF formulations has gained significant attention due to advances in computational power and new theoretical developments in approximations of the non-linear AC power flow equations [1], [14], [15]. The use of the full non-convex AC power flow model becomes computationally demanding once intertemporal constraints and large-scale DNs are considered [16], whereas the DC power flow approximation is not appropriate for DNs as the voltage magnitudes are typically not close to nominal and branch resistances are significant.…”

“…It has been used in OPF formulations [1]- [3] as it can be easily incorporated in the mathematical formulation, shows high accuracy in DNs, and leads to convex problems that can be efficiently solved. In this paper, we consider such a BFS-OPF problem formulation which can handle weakly meshed DN configurations, is computationally tractable and derives AC feasible solutions.…”

“…After we obtain the optimal OPF setpoints, we perform an exact BFS power flow to derive an AC feasible operating point (in contrast to [1] where only one BFS iteration is used), whose solution for the lateral voltages will be used in the next OPF iteration. The loop is repeated until convergence in terms of voltage magnitude mismatch is reached.…”