Coordinated two-stage volt/var management in distribution networks

Abstract

This paper investigates daily volt/var control in distribution networks using feeder capacitors as well as substation capacitors paired with on-load tap changers. A twostage coordinated approach is proposed. Firstly, the feeder capacitor dispatch schedule is determined based on reactive power heuristics. Then, an optimisation model is applied to determine the dispatch schedule of the substation devices taking into account the control actions of the feeder capacitors. The reference voltage of the substation secondary bus and the tap position limits of transformers are modified such that the model adapts to varying load conditions. The optimisation model is solved with a modified particle swarm optimisation algorithm. Furthermore, the proposed method is compared with conventional volt/var control strategies using a distribution network case study. It is demonstrated that the proposed approach performs better than the conventional strategies in terms of voltage deviation and energy loss minimisation.Dispatch of the volt/var control (VVC) resources can be performed in a coordinated manner in constrained environments to meet specific operational objectives [2, 3, 4, 5 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17]. The complexity of the objective function, constraints, and computation is influenced by, among others: regulatory limits, switching limitations and available control devices. The focus of this paper is daily VVC with switching restrictions, which is usually applied to networks with widespread communication and control coverage [7,8,9,10, 11,12,13,14,15,16,17]. The ad-10 ditional requirement of this VVC approach is a day-ahead forecast of load behaviour, which is made possible by the existence of load forecasting techniques that provide good accuracy [18], [19].Daily coordinated control of all distribution devices is computationally complex, but there are a number of ways to deal with this difficulty. One way to approach this is to 15 simplify the solution space so as to reduce the computational burden. For instance, the requirements of dynamic programming can be eased according to [8], [9], [11], while a more efficient solver based on the interior-point method is presented in [17]. In [10] the number of possible states is decreased by combining artificial neural networks, a rulebased method and dynamic programming. Use of heuristic rules can also reduce the 20 number of possible device operations, therefore simplifying the optimisation model [13].These methods address the issue of computational complexity but the requirements for remote control infrastructure remain for network-wide implementation. Another alternative is to divide the scheduling problem into two sub-problems: one handling the dispatch of the substation capacitor (SC) and OLTC, and the other controlling the 25 feeder capacitors (FCs) [12]. In particular, dispatch of the substation devices minimises reactive power-flow and the voltage deviation at the substation bus. FCs are then dispatched based on local bus voltage and power factor devi...

A review on economic and technical operation of active distribution systems

“…This method can considerably enhance the interactions between transmission networks and DERs. In [36], the authors present a two-stage daily Volt/Var management approach in DNs using feeder capacitors and substation capacitors joined with OLTCs. In the first stage of Volt/Var management, a dispatch schedule for the feeder capacitors is specified based on reactive power heuristics.…”

A Two-Loop Hybrid Method for Optimal Placement and Scheduling of Switched Capacitors in Distribution Networks

“…In [11], a modified PSO algorithm is used to implement optimized Volt/VAr control by utilizing switched capacitors and on-load tap changers. Binary PSO is used in [12] for optimal circuit reconfiguration and switching of capacitors to minimize the loss.…”

Optimal coordination of PV smart inverter and traditional volt‐VAR control devices for energy cost savings and voltage regulation

“…Recently, several papers have been published on volt‐VAR optimization (VVO) . Kumar et al adopted particle swarm optimization (PSO) to determine optimal setting of VVC devices considering wind energy for energy savings.…”

“…Paudya et al presented an optimal operation of the distribution system with the objective of minimizing energy drawn from substation with reduced switching number of taps and capacitors. Mokgonyana employed a modified particle swarm optimisation algorithm for optimal volt/VAR control in distribution networks. Madureira et al employed evolutionary PSO (EPSO) for optimal coordination of a coordinated voltage control scheme.…”