Energy Storage Sizing and Probabilistic Reliability Assessment for Power Systems Based on Composite Demand

This paper presents an energy storage system (ESS) sizing model and reliability assessment framework to quantify reliability improvements due to ESS of electric energy systems with high penetration of renewables. The model formulation takes into account: (a) variable generation (VG) forced outage rates (FORs), (b) reserve and demand requirements, and (c) conventional generation (CG) operational constraints and practices. Correlation coefficients among wind speed, solar radiation, and demand are computed using the least square estimation method (LSE). Depending on the correlation, probabilistic models for the composite demand are computed and integrated into the ESS sizing model. Subsequently, the ESS optimal sizes are computed along with the ESS optimal charging and discharging schedules. Then, the reliability is quantified using the probabilistic production costing (PPC) method. A case study is presented in which one VG was approximated as independent variable because of its low correlation with demand and other VG. The case study compares the error when treating the VG as independent.

I. Introduction

Reliability relates to the ability that a system or equipment performs its intended function over a time interval [1]. This definition when applied to power systems has two aspects: adequacy and operational reliability (security) [2]. Adequacy, which is the concern in this study, relates to sufficiency of the electricity resources to ensure continuity of service to end-users.