Time series power flow analysis for distribution connected PV generation.

Abstract

Distributed photovoltaic (PV) projects must go through an interconnection study process before connecting to the distribution grid. These studies are intended to identify the likely impacts and mitigation alternatives. In the majority of the cases, system impacts can be ruled out or mitigation can be identified without an involved study, through a screening process or a simple supplemental review study. For some proposed projects, expensive and timeconsuming interconnection studies are required. The challenges to performing the studies are twofold. First, every study scenario is potentially unique, as the studies are often highly specific to the amount of PV generation capacity that varies greatly from feeder to feeder and is often unevenly distributed along the same feeder. This can cause location-specific impacts and mitigations. The second challenge is the inherent variability in PV power output which can interact with feeder operation in complex ways, by affecting the operation of voltage regulation and protection devices.The typical simulation tools and methods in use today for distribution system planning are often not adequate to accurately assess these potential impacts. This report demonstrates how quasi-static time series (QSTS) simulation and high time-resolution data can be used to assess the potential impacts in a more comprehensive manner. The QSTS simulations are applied to a set of sample feeders with high PV deployment to illustrate the usefulness of the approach. The report describes methods that can help determine how PV affects distribution system operations. The simulation results are focused on enhancing the understanding of the underlying technical issues. The examples also highlight the steps needed to perform QSTS simulation and describe the data needed to drive the simulations. The goal of this report is to make the methodology of time series power flow analysis readily accessible to utilities and others responsible for evaluating potential PV impacts. 4 ACKNOWLEDGMENTSMatthew Lave for assistance with the Wavelet-based Variability Model. Wes Sunderman for assistance with the Open Distribution System Simulator. 5

Impacts of Voltage Control Methods on Distribution Circuit’s Photovoltaic (PV) Integration Limits

“…The undesirable impacts of high percentages of PV integration call for the study to determine the circuit's PV hosting capacity [13][14][15][16][17][18][19][20][21][22][23]. Given a large number of potential PV deployment scenarios, researchers have primarily looked into simulation-based frameworks [13][14][15][16][17][18][19][20][21][22].…”

“…In literature, several methods have been proposed to determine the feeder's maximum PV penetration limits [12][13][14][15][16][17][18][19][20][21][22][23][24][25][26]. These methods are briefly discussed in Section 1.1.…”

Grid integrated distributed PV (GridPV).

“…Time-series simulations are very important to understand the impact of the variability of solar and to characterize the time-dependent aspects of the system [8,9]. To perform a time-series analysis there are two options.…”

“…%% Feeder Power Factor DSSText.Command = 'export mon fdr_05410_Mon_PQ'; monitorFile = DSSText.Result; MyCSV = importdata(monitorFile); delete(monitorFile); Hour = MyCSV.data(:,1); Second = MyCSV.data(:,2); feederPower = MyCSV.data(:, [3,5,7]); feederReactivePower = MyCSV.data(:, [4,6,8]);…”

Formulating a simplified equivalent representation of distribution circuits for PV impact studies.

“…Interconnection studies are required to study the impacts of high deployment levels of PV on a distribution system when the PV levels exceed screening thresholds for fast track approval [1]. A full detailed model of the distribution system can be time consuming to produce, and a timeseries simulation of a large system at a high time-resolution requires significant computational processing [2][3][4].…”