2014 PV Distribution System Modeling Workshop: Data and Models for High Penetration Using Advanced...

Roger C. Dugan

Sr. Technical Executive

Sandia-NREL-EPRI PV Distribution System Modeling Workshop

May 6, 2014

Santa Clara, CA

Data and Models for High-Penetration

PV Using Advanced Inverters

2 © 2014 Electric Power Research Institute, Inc. All rights reserved.

Objective

• Data and modeling requirements for advanced, or smart,

inverter functions will be illustrated using the modeling

requirements for the EPRI OpenDSS program


The OpenDSS PVSystem Model With Smart

Inverter Control Can Demonstrate Benefits


The basic volt-var control function can be

described by four P, Q points

This control is effective where the voltage level will respond to

vars – where the system impedance is Inductive


Adding hysteresis to the volt-var curve is

sometimes beneficial in controlling voltage

Implementations of this model may require more points simply

implement shifting logic to a base curve


Modeling the advanced inverter is demonstrated

with an OpenDSS example based on this circuit


An actual 10-min PV system Active Power

measurement will be used for the example

New "LoadShape. PV_ls" npts=600 sinterval=1.0 mult=(File=“Solar-600s.csv")

OpenDSS Script for Defining This as a “Loadshape”: File containing 600 pts


This OpenDSS script snippet defines the four

PV systems

New PVSystem.3P_ExistingSite4 phases=3 bus1=B51854_sec kV=0.4157 kVA=523

~ irradiance=1 Pmpp=475 pf=1 %cutin=0.1 %cutout=0.1 yearly=PV_ls

New PVSystem.3P_ExistingSite1 phases=3 bus1=X_5865228330A kV=0.4157 kVA=314


New PVSystem.3P_ExistingSite3 phases=3 bus1=X_5891328219_Cust1 kV=0.4157

~ kVA=836 irradiance=1 Pmpp=760 pf=1 %cutin=0.1 %cutout=0.1 yearly=PV_ls



•Bus Name (Bus1)

•Voltage rating (kV)

•kVA rating (kVA)

•Base irradiance (kW/m2)

•Power at MPP (Pmpp)

•Base power factor (pf)

•Cut in/cut out percentage values

•Irradiance Loadshape for OpenDSS solution mode (yearly in this case to get desired

monitoring)

•Inverter Efficiency curve (optional)

•Pmpp vs Temperature curve (optional)

Data for PVSystem Model


The base-line simulation reveals voltage and

power excursions

Note: Unity PF assumed for base-line


Implementation of a simple volt-var control

requires definition of a curve and an InvControl

New XYCurve.vv_curve npts=4 Yarray=(1.0,1.0,-1.0,-1.0) XArray=(0.5,0.95,1.05,1.5)

New InvControl.InvPVCtrl mode=VOLTVAR voltage_curvex_ref=rated

~ vvc_curve1=vv_curve EventLog=yes

Volt-Var Control Curve Definition

Inverter Control Definition

pu Voltage pu Rated Vars


Results with simple volt-var control show the

voltage is reduced about 2% to less than 105%


Modeling hysteresis is accomplished by adding

an offset to the voltage (x axis)

New XYCurve.vv_curve npts=4 Yarray=(1.0,1.0,-1.0,-1.0) XArray=(0.5125,0.9625,1.0625,1.5125)


~ vvc_curve1=vv_curve hysteresis_offset=-0.025 EventLog=yes


The reactive power output level is constant

when power flow between curves


The solutions on the VV curves with hysteresis

indicate the inverter drawing vars to reduce V


Volt-Var control with adaptive set point attempts

to follow the voltage more closely over time

New InvControl.InvPVCtrl mode=VOLTVAR voltage_curvex_ref=avg avgwindowlen=2m

~ vvc_curve1=vv_curve EventLog=yes


Adding a 5-s time constant on the rate of

change significantly smooths the var response


~ vvc_curve1=vv_curve RateofChangeMode=LPF LPFTau=5 EventLog=yes

Data Requirements for Other Control

Functions


The Volt-Watt Function suppresses active

power output for high voltages

New XYCurve.examplevoltwattcurve npts=4 Yarray=(1.0,1.0,0.0,0.0) XArray=(0.0,1.0,1.1,2.0)

New InvControl.InvPVCtrl mode=VOLTWATT voltage_curvex_ref=rated

~ voltwatt_curve=examplevoltwattcurve EventLog=yes

Optional DATA:

Rolling average window length

Units for Y axis

Rate-of-change mode: INACTIVE | LPF | RISEFALL

Low-Pass Filter time constant for rate of change of output power

RiseFall Limit (pu/s or kW/s)


The Dynamic Reactive Current function provides reactive current in

response to dynamic variations in voltage

New InvControl.InvTestPVCtrl mode=DYNAMICREACCURR DbVMin=0.975 DbVMax=1.025

~ ArGraLowV=10.0 ArGraHiV=10.0 DynReacavgwindowlen=120s EventLog=yes

Optional DATA:

Var change tolerance; default is 0.025 pu of available vars


The Dynamic Reactive Current control can help reduce

voltage sags and swells during transient events


Fixed Power Factor control is a simple function

that reduces voltage swings and high voltages


~ irradiance=1 Pmpp=475 pf=-0.98 %cutin=0.1 %cutout=0.1 yearly=PV_ls


This example of the Max Generation Limit function limits

PV system output to 70% or Pmpp


~ irradiance=1 Pmpp=475 kvar=0.00 pctPmpp=70.0 %cutin=0.1 %cutout=0.1

~ yearly=PV_ls


This example demonstrating OpenDSS scripting

for switching from V-W control to V-V control

New XYCurve.myvw_curve npts=4

~ Yarray=(1.0,1.0,0.0,0.0)

~ XArray=(0.5,1.0,1.05,1.5)

New InvControl.InvTestPVCtrl mode=VOLTWATT

~ voltage_curvex_ref=rated

~ voltwatt_curve=myvw_curve EventLog=yes

set casename= voltwatt300_voltvar300

solve mode=yearly number=300 stepsize=1s

New XYCurve.myvv_curve npts=4

~ Yarray=(1.0,1.0,-1.0,-1.0)

~ XArray=(0.5,0.95,1.05,1.5)

InvControl.INVPVCTRL.mode=VOLTVAR

InvControl.INVPVCTRL.voltage_curvex_ref=rated

InvControl.INVPVCTRL.vvc_curve1=myvv_curve

Solve number=300


“Loadshape” data, typically in 1-s intervals, is

key to many advanced inverter simulations


Questions?

2014 PV Distribution System Modeling Workshop: Data and Models for High Penetration Using Advanced...

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