Framework for Extracting and Characterizing Load Profile Variability Based on a Comparative Study of Different Wavelet Functions

Abstract

The penetration of distributed energy resources (DERs) on the electric power system is changing traditional power flow and analysis studies. DERs may cause the systems' protection and control equipment to operate outside their intended parameters, due to DERs' variability and dispatchability. As this penetration grows, hosting capacity studies as well as protection and control impact mitigation become critical components to advance this penetration. In order to conduct such studies accurately, the electric power system's distribution components should be modeled correctly, and will require realistic time series loads at varying temporal and spatial conditions. The load component consists of the built environment and its load profiles. However, large-scale building load profiles are scarce, expensive, and hard to obtain. This paper proposes a framework to fill this gap by developing detailed and scalable synthesized building load profile data sets. Specifically, a framework to extract load variability characteristics from a subset of buildings' empirical load profiles is presented. Thirty-four discrete wavelet transform functions with three levels of decomposition are used to extract a taxonomy of load variability profiles. The profiles are then applied to modeled building load profiles, developed using the energy simulation program EnergyPlus ® , to generate synthetic load profiles. The synthesized load profiles are variations of realistic representations of measured load profiles, containing load variabilities observed in actual buildings served by the electric power system. The paper focuses on the framework development with emphasis on variability extraction and application to develop 750 synthesized load profiles at a 15-minute time resolution. INDEX TERMS Load profile, building energy modeling, electric power system, distributed energy resources, wavelet functions, discrete wavelet transform.

A Case Study to Quantify Variability in Building Load Profiles

“…Specifically, accurate power flow studies in the electrical grid must consider these fluctuations to guarantee electrical system flexibility, reliability, and operation without compromising system performance. By increasing the utilization of DERs, electrical system operation, control, economy, and planning studies become critical to meet the target DER penetrations [1]. When DER is interconnected to the distribution system, conventional distribution studies and special system impact studies methodologies need to be considered as explained in IEEE Std 1547.7 [1], [2].…”

“…By increasing the utilization of DERs, electrical system operation, control, economy, and planning studies become critical to meet the target DER penetrations [1]. When DER is interconnected to the distribution system, conventional distribution studies and special system impact studies methodologies need to be considered as explained in IEEE Std 1547.7 [1], [2]. Hence, correct modeling of the distribution systems' components is key to conducting accurate studies, which require time-series data of the relevant loads at varying temporal and spatial conditions [1].…”

“…When DER is interconnected to the distribution system, conventional distribution studies and special system impact studies methodologies need to be considered as explained in IEEE Std 1547.7 [1], [2]. Hence, correct modeling of the distribution systems' components is key to conducting accurate studies, which require time-series data of the relevant loads at varying temporal and spatial conditions [1]. IEEE Std 1547.7 (2013) states that "Multiple power flow simulations including time series or quasi-static simulations may be needed to fully study the impacts of DR [distributed resources] on Area EPS [Electric Power System] voltage" ( [2], page 8).…”

“…IEEE Std 1547.7 (2013) states that "Multiple power flow simulations including time series or quasi-static simulations may be needed to fully study the impacts of DR [distributed resources] on Area EPS [Electric Power System] voltage" ( [2], page 8). Furthermore, the IEEE standard describes quasi-static simulations: "Quasi-static simulation refers to a sequence of steady-state power flow conducted at a timestep of no less than 1 second but that can use a time step of up to one hour" ( [2], page 77) [1]. For example, authors in [3] studied the impact of PV systems on electrical systems using quasi-static time-series (QSTS) simulations.…”

“…EnergyPlus is able to generate modeled load profile data, based on set schedules and parameters, at various timescales, ranging from oneminute to one hour. However, the developed load profiles contain less variability than what actually takes place in real buildings [1]. In other ongoing work by the authors, one application of variability load profiles is utilized to generate synthetic load profiles that resemble real building load profiles [1].…”