Achieving the Dispatchability of Distribution Feeders Through Prosumers Data Driven Forecasting and Model Predictive Control of Electrochemical Storage

Abstract

Abstract-We propose and experimentally validate a process to dispatch the operation of a distribution feeder with heterogeneous prosumers according to a trajectory with 5 minutes resolution, called dispatch plan, established the day before the operation. The controllable element is a utility-scale grid-connected battery energy storage system (BESS) integrated with a minimally pervasive monitoring infrastructure. The process consists of two stages: day-ahead, where the dispatch plan is determined by using forecast of the aggregated consumption and local distributed generation (prosumption), and real-time operation, where the mismatch between the actual prosumption realization and dispatch plan is compensated for thanks to adjusting the real power injections of the BESS with model predictive control (MPC). MPC accounts for BESS operational constraints thanks to reduced order dynamic grey-box models identified from online measurements. The experimental validation is performed by using a grid-connected 720 kVA/500 kWh BESS to dispatch the operation of a 20 kV distribution feeder of the EPFL campus with both conventional consumption and distributed photo-voltaic generation.

Performance Assessment of Linearized OPF-based Distributed Real-time Predictive Control

“…2a shows the prosumption at the GCP for the 3 days. The dispatch plan is computed using the procedure described in [2], and it is shown in Fig. 2b.…”

“…, T the time indices spanning from the time t∆t to the end of the control horizon T ∆t, and 1) , and q unc t ∈ R (n b −1) the uncontrollable active and reactive power nodal injections (obtained by measurement for the time t∆t, and by forecasts for subsequent intervals t∆t). The three update policies are: 1) the SCs are computed using a single operating point and kept fixed throughout the control horizon; A t and b t can be expressed as 1,2 :…”

“…We consider a distribution grid interfacing a cluster of controllable units and uncontrollable prosumption that is dispatched at its GCP according to a pre-determined dispatch plan. The dispatch plan, computed as in [2], is an optimal power consumption trajectory over a certain horizon (e.g., 5-minute resolution for the next 24 hours) computed before operation (e.g., the day-ahead). It is the sum of two elements: i) point predictions of the aggregated uncontrollable prosumption, and, ii) offset profile of each flexible resource, responsible to embed into the dispatch plan the energy demand required to restore optimal levels of flexibility in the controllable resources.…”

“…Dispatching distribution networks to track a predefined dispatch plan at the grid connection point (GCP) has been proposed in the literature as a way to achieve the coordination between transmission networks and distribution systems (e.g. [1], [2]) and avoid the activation of expensive reserve. The work in [3] proposed a control scheme based on the alternating direction method of multipliers (ADMM) to coordinate the operations of heterogeneous resources and track the dispatch plan.…”

“…CIGRÉ low voltage benchmark network[13] (a) Prosumption at the GCP for three days. (b) Dispatch plan at the GCP for three days computed using[2]. (c) MPP PV forecast for three days.…”