Voltage and Var Control Applications Including Smart Inverters, Energy Storage, and Secondary Side Solutions

Dr. Arindam Maitra, EPRI

Dr. Jason Taylor, EPRI

IEEE PES Meeting, Denver July 29th, 2015

1

Industry Issue

Distribution Planning and Operations are Becoming More Complex

• Traditional methods of managing voltage and reactive power rely on voltage regulators and capacitor banks

• New requirements like peak demand reduction, VVO/CVR for load management are requiring new coordination challenges

• Emerging DER along edge of the n/w

• Autonomous units not well-coordinated with conventional capacitors, voltage regulators and load-tap changers

VVO/CVR

Processor

RTU

End of Line

Voltage

Feedback

Standalone

Model-based

Rule-based

LTC Control

RTU

VVC Processor

Substation

116

118

120

122

124

126

1 1.5 2 2.5 3 3.5 4 4.5 5

Cap banks, Vreg

Cap banks, Vreg,

plus Smart

inverters

Uncertainty and Future of the Distribution System

Distance from Substation

Vo

lta

ge

• Replace xfmr

• Reconductor

• Line Tap Changer (LTC)

• Cap bank

• Line regulators

Traditional Regulation Options Benefits of CVR and VVO: - Lower losses in lines, transformers - Lower losses in end-use devices - Allows more real-power throughput

Vo

ltag

e

Distance from Substation

Upper Threshold

Lower Threshold

Volt/Var Optimization

Smart Inverters

Storage

Power Electronic Devices

Potential Benefits – Faster response

– Flatter voltage profile

– Direct placement for localized problems

Distributed Voltage Regulation

Grid Impacts of Intermittent Distributed Resources

Source: EPRI

Cap

Bank Substation

(LTC)

distribution line LVR

0.9

0.92

0.94

0.96

0.98

1

1.02

1.04

#1 #3 #5 #7 #9 #11 #13

vo

lta

ge

highest

voltage

lowest

voltage

va

riatio

n o

ve

r tim

e

Limited voltage control

Centralized Control

Distributed Secondary Side Volt-VAR Control

Secondary Side Control

0.9

0.92

0.94

0.96

0.98

1

1.02

1.04

#1 #3 #5 #7 #9 #11 #13

vo

lta

ge

Improved voltage control

Distributed Control

Cap

Bank Substation

(LTC)

distribution line LVR

Distributed Secondary Side Volt-VAR Control

Secondary Side Control

Numerous Potential Performance Objective(s)

Efficiency

• Reduced distribution line losses

• Improved customer efficiency CVR

• Peak Demand reduction

Power Quality

• Flatter voltage profile

• Improved harmonics

• Voltage flicker

• Overvoltage

Asset Utilization

• Reduce LTC tap changes

• Reduce line regulator tap changes

• Reduce switch cap changes

• Deferment of system upgrades

Reliability • Momentary interruption support

• Automatic reconfiguration support

Enabling • Increased DER hosting capacity

Smart Inverters

Reactive power dispatch

– Output constrained by active power generation

– Multiple control configurations (settings)

Industry Adoption • IEEE standard 1547 • California Rule 21 • Manufacturers onboard

0 5 10 15 20 25

1.024

1.026

1.028

1.03

1.032

1.034

1.036

1.038

1.04

1.042

1.044

Hour

Vo

lta

ge

(p

u)

Voltages with different voltvar settings

---- Voltvar

---- No PV

---- PV base

What is the best voltage response?

Depends on the objective

Response using different volt-var settings

Capacitor switching or inverter status change

Control Settings Specification depends upon…

Control Design Sensitivities Time-series, stochastic assessments • Spatial variation • Temporal variation

performance

objective

network

characteristics

inverter

rating

… as well as Operational Conditions

Formulation of control design practices is needed

Energy Storage Four-quadrant Operation

• Voltage regulation using both active and reactive power

Test Feeder Evaluation

• Large voltage variations due to PV

• Storage to provide voltage regulation

• Various deployments considered

Figure Error! No text of specified style in document.-1

PV systems for 57305 feeder

PV Systems for 57307 feeder

Regulator

Substation and meter

Capacitors

PV system

Distance measured from the meter

1.6 miles

1.612 miles

1.579 miles

1.273 miles

1.148 miles

Effect of Energy Storage Location on Voltage

0 0.05 0.1 0.15 0.2

PV Ramp UP

PV Ramp DOWN

Largest Voltage variation (%)

With Energy Storage No Energy Storage

0 0.5 1 1.5 2

PV Ramp UP

PV Ramp DOWN

Largest Voltage variation (%)

With Energy Storage No Energy Storage

0 0.5 1 1.5

PV Ramp UP

PV Ramp DOWN

Largest Voltage variation (%)

With Energy Storage No Energy Storage

0 0.5 1 1.5

PV Ramp UP

PV Ramp DOWN

Largest Voltage variation (%)

With Energy Storage No Energy Storage

The voltage profile improves for each bus. The largest voltage variations at PV buses decrease from 0.014 pu to 0.002 pu.

At PV Bus 2

At PV Bus 1

At Feeder End 1

At Substation

210kW/735kWh

450kW/1575kWh

2.14MW/7.6MWh

Energy Storage absorbs or generates only active power (Volt/Watt Control)

Effect of Energy Storage Location on Voltage Regulation

00.20.40.60.8

11.21.41.6

Largest voltage variation at PV Bus 2

PV Ramping Up PV Ramping Down

Storage Location

Larg

est

volt

age

vari

atio

n (

%)

The voltage regulation concerns are demonstrated using PV bus 2

As ES moves away from PV location, the improvement in voltage variation decreases.

PVBus_2

PVBus_1

Energy Storage absorbs or generates only reactive power (Volt-Var Control)

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

Re

du

ctio

n in

Vo

ltag

e V

aria

tio

n (

%)

Storage Location

Active Power Reactive Power

General Study Circuit Findings

Impacts are location and circuit specific

• Distance from PV

• System strength

• X/R ratio

Active power injection or absorption may better counteract the variations

Voltage at PV Bus 2

Increasing distance from Substation

Example Secondary Side Voltage Management Solutions

ENGO-V10 (Varentec)

Shunt connected

240V, 1-phase

0-10 kvar (leading)

Voltage and power factor control

60/50 Hz

IPR-50 (GridCo)

In-line Power RegulatorTM

240V, 1-phase

50 kVA

Regulation ±10%

±5 kvar

60 Hz

To LoadTo Source

Shunt Current

Source

Bypass Switch

Series Injection

Transformer

Series

Voltage

Source

B. McMillan, et al., "Application of Power Electronics LV Power Regulators in a Utility Distribution System," in Rural Electric Power Conference (REPC), 2015 IEEE, 2015.

ENGO-V10 Product Overiview, http://varentec.com

Example European Devices PCS 100 AVR (ABB)

Active Voltage Regulator (AVR)

400 V, 3-phase

400 kVA

50 Hz

± 10% correction

Regulation accuracy ± 1 (typical)

LVRSysTM (a-eberie)

Low Voltage Regulator System

400 V, 3-phase

55 – 400 kVA

50 Hz

± 6% (± 10% extended range)

9 steps, 1.5% (2.5%)

To Load

To Source

Rectifier

& Inverter

Bypass

Boost

transformer

(if not 400/480

V supply)

Distribution

Transformer

To LoadSource

(per-phase)

TR2TR1

Thyristor Control

“Case Study - PSC100 Active Voltage Regulator (AVR): Voltage Regulation for Utility Grids with Distributed Generation,” ABB, www.abb.com/powerquality

“Low Voltage Regulator System: Technical Data,” ABB, http://www.a-eberle.de

Continuing Efforts

Modeling and Simulation

• Models of emerging devices

• Simulation capabilities for advanced distribution automation

• Actual circuit evaluations

• Model validation

Planning & Design

• Impact (coordination) with existing (other) voltage regulation components

• Coordination/integration with DMS

• Determination of control settings practices

• Device location and sizing practices