Feeder Voltage Stabilization

Using distribution class equipment

Outline IPL WPL Total

Electric Customers 490,595 471,526 962,121

Electric Retail Sales (000s MWh) 14,356 10,739 25,095

Electric Wholesale Sales (000s MWH)

1,338 2,301 3,639

Summer Peak Demand (MW) 2,968 2,476

Gas Customers 224,041 189,013 413,054

Gas Sales (000s Dths) 65,945 60,221 126,166

Operating Revenues (millions) $1,870 $1,473 $3,382

Alliant Energy – Regulated Utility Profile

• Overview of Alliant Energy • Overview of selected device • Example of Capital Deferral

• Single Phase • Example of Voltage/System Stability

• Wind • Maximizing System/Solar Capacity

• Future use case microgrid with STATCOMs to limit battery locations on highly loaded or long feeders

• Summary

Overview – Use case for STATCOM

• Solar penetration • Voltage Stability • Power Quality • Easy integration • Autonomous Operation • Single device with long reach

• Device looks and installs similar to a set of Voltage Regulators

• Operates dynamically • Does not have physical switching

• Power Electronics connected directly to the primary voltage

• Self diagnostics • Alliant Energy monitors and stores operational

and planning data • Use AMSC SCADA for detailed data collection

and device analysis • We opted to sign a service contract with

vendor to maintain proper expertise (versus training internal crews across the service territory)

Overview - DVAR VVO STATCOM

• 1ph tap off a 3ph line with high voltage • 1ph tap has solar on most farms and homes • Distance of 1ph tap is 15 miles • 1ph tap off 3ph line is 8 miles from substation

• Weak three phase system with significant solar

• Point 9 has significant voltage swing • Traditional solution: 1ph to 3ph, phase balance,

reconductor, voltage conversion • One single phase device prevented all rebuilds,

reconductoring, and voltage conversions • $215K versus $1.6 million

Utility Application Case 1: High DER/Solar Generation (commercial and residential)

Single-Phase ±343 kVAR D-VAR VVO™ STATCOM

G

G

G G G G

G G

G

G G G G

G

G

G

G G

G G

G

G

F 1 2

4

3

5

6

7

8

9

10

11

12

13

B-Phase Network

• As the PV solar generation changes throughout the day, the voltage varies widely

• Sudden changes in the voltage happen before traditional utility equipment can respond

Problem: Voltage Variation

• Since installation of STATCOM on this 15 mile tap, solar doubled from 150kW to over 300kW

• The STATCOM has done it’s job without any intervention and is still operating within it’s capabilities

• By using ONE device that can ‘see’ in both directions and stabilize voltage within regulatory requirements (based adoption rates) - this is an excellent design

Single Phase DVAR VVO

• Over three days there were over 130 voltage violations (over 5%) with no dynamic regulation • Device successfully held the voltage between 121V and 123V

How Many Voltage Violations?

One Month Voltage Profile

-200

-100

0

100

200

300

400

500

600

0.9

0.92

0.94

0.96

0.98

1

1.02

1.04

1.06

7/9/19 0:00 7/14/19 0:00 7/19/19 0:00 7/24/19 0:00 7/29/19 0:00 8/3/19 0:00 8/8/19 0:00 8/13/19 0:00

13.2

kV V

olta

ge, P

ositi

ve S

eque

nce,

Per

Uni

t

Washington D-VAR VVO Installation 9 July 2019 - 13 August 2019 Actual Voltage Vs Calculated Uncorrected Voltage & VVO kVAR Output

pos seq Uncorrected Phase pu kVAR

13.2kV Voltage, Without VVO (Calculated)

13.2kV Voltage, With VVO (Measured)

VVO kVAR Output (Measured)

• STATCOM only 1/3 taxed with current profile/feeder condition

• 2020 will be dedicated to developing guidelines for using selective storage placement with STATCOMs

• Wind Generation at end of feeder

Utility Application Case 2: Three phase device w/Wind Generation

• From Wind at no output to wind at 2.4MW, voltage is within 1% of voltage set point

• Feeder had no solar capacity – adding device solved the problem and allows increased capacity of solar (by residential customers)

• Location is more straight forward with Wind – voltage violations are concentrated in one location

• This is closely related to a CVR application where we leveled the voltage over the entire feeder • Because of the capacitive and inductive

capability of the DVAR VVO, CVR is an excellent application

• By lowering the head of circuit voltage, capacity factor increases

• Solution replaces two mechanically switched devices

Results – DVAR VVO w/Wind

• Feeder already at maximum capacity • Existing customer wants to add 260kW of new solar to 800kW

• Based on Regulatory requirements we should have rejected the application

• Customer would install batteries and not backflow • Rejection would solve the immediate utility grid

problem, but introduced many other problems, short and long term

Utility Application Case 3: High solar penetration and load growth

High solar penetration

Customer adding 260kW solar

• Solution was to install a 3ph STATCOM one mile up steam from the large solar

• The study suggests at end of line we could maintain regulatory voltage requirements.

• Little/no additional capacity was available

High solar penetration

Battery

• Installation offset $2.5 million of rebuilds (which included a voltage conversion)

• Least cost solution • With both batteries and STATCOM

we are able to stabilize the voltage across the feeder, address customers issues, and increase adoption rate (batteries and STATCOM) to a level beyond what is anticipated by load growth in the area

• In other words, we have created an island of stability with flat voltage, and the potential for islanding

DVAR VVO

Feeder goes north, and south

Potential DVAR VVO

Personal Commentary and Conclusion

• The distribution system is changing from sending energy from the transmission system to distributing energy from local resources • Utilities will need to prioritize optimization of local generation • Current rate structures have significant lag (volume rates versus fixed costs)

• Current feeder topology can be supported – save massive $ • STATCOM’s can solve most capacity factor problems, without expensive

rebuilds • If adoption rates are higher than load, STATCOMs can increase capacity factor • Adoption rates vary by many factors but must be added to distribution

planning • Future systems will require dynamic stabilization due to the high cost of storage at

many locations along a feeder, especially for rural customers • Direct primary connected STATCOM’s offer great Cost/Benefit and flexibility

Q&A