# Identification and Validation of Virtual Battery Model for Heterogeneous Devices

## TL;DR

This paper develops a first-order virtual battery model to accurately represent the aggregate flexibility of heterogeneous distributed energy resources, enabling improved demand side control for grid services.

## Contribution

It introduces a novel identification framework for virtual battery parameters in heterogeneous DER ensembles, including time-varying power limits calculation.

## Key findings

- Effective virtual battery modeling for heterogeneous DERs.
- Improved demand response performance through optimized virtual battery parameters.
- Validation on ensembles of air conditioners and water heaters.

## Abstract

The potential of distributed energy resources in providing grid services can be maximized with the recent advancements in demand side control. Effective utilization of this control strategy requires the knowledge of aggregate flexibility of the distributed energy resources (DERs). Recent works have shown that the aggregate flexibility of DERs can be modeled as a virtual battery (VB) whose state evolution is governed by a first order system including self-dissipation. The VB parameters (self-dissipation rate, energy capacity) are obtained by solving an optimization problem which minimizes the tracking performance of the ensemble and the proposed first-order model. For the identified first order model, time-varying power limits are calculated using binary search algorithms. Finally, this proposed framework is demonstrated for different homogeneous and heterogeneous ensembles consisting of air conditioners (ACs) and electric water heaters (EWHs).