04/10/23 1

690 VGrid

PM Generator

690V

690VAC, 460 Amps

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3 Phase2.5MW 690 V

By: Dr. Sammy Germany

04/10/23 2

Background: To achieve low cost of energy, turbine manufacturers have

traditionally focused on: • Component cost• Component reliability• Variable speed applications to capture more low wind

speed energy

More recent industry trends have focused on • PMG - energy capture in wider wind speed range• High efficiency & Reducing O&M costs• Designs for lower class sites (Class 3)

Power System Focus – Availability + Uptime• Uptime is the key to capture more energy• Diminishing returns for

power component MTBF power component MTTR

Uptime kWh

Energy: Power & Time

04/10/23 3

Modular Multi-MW Converters

PM Generator

690V 690V

690V Multi

Three-Phase Set Generator

35kV

High Reliability – High Availability

1. Designs are built to be reliable, tough inverters 2. Mechanical robustness to reduce O&M costs in harsh

turbine environments 3. Modularity: Operational redundancy, increasing

availability of system even under fault conditions

Cap

acity

100%

Failure event MTTR

Without redundancy

Withredundancy

time

Energy Savings w/ redundancy

04/10/23 4

Class 4 - 30 MW Wind Farm Met Data

0

2

4

6

8

10

12

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

Month

Win

d S

pee

d m

/s)

0.00

0.10

0.20

0.30

0.40

0.50

0.60

0.70

0.80

0.90

1.00

Per

Un

it T

urb

ine

Po

wer

(M

W)

Wind Speed (m/s)

Average Power

• Class 3-4 Wind farm met data used for energy harvesting case studies• Peak hourly wind speed average 80% - Optimal for parallel units. • 10 Towers, 3MW turbines

Turbine Power

Month

04/10/23 5

What is the problem? Lost revenue from non-operation turbines increased the cost of energy in large wind farms.

• Turbine repairs occur after multiple turbines have failed (high O&M costs)• In large farms, 3-5 turbines may need to be down before serviced (up to 3 months)• Long MTTR of wind turbines impacts energy capture rates.

How significant is it for a 30MW Wind Farm?• $6.6M : Yearly energy revenue for a Class 4, 30MW wind farm (6.5 c/kW.hr)

• $330k (5%): Yearly lost revenue from 3 turbine failures with 3 months downtime.

Benefits of a DRS Power System Solution:

• If one (1) turbine failure is due to an inverter, the module remains operating and capturing energy.

• $165k Savings: 2.5% of wind farm’s yearly revenue

NPV: $0.8M – 1.8M for 1 to 2 power failures / yr over life of wind farm (20yrs)

(Considering increased energy generated due to uptime and the cost of power system modularity)

04/10/23 6

690 VGrid

PM Generator

690V

690VAC, 460 Amps

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=~

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3 Phase2.5MW 690 V

Topology Description• 500kW 690V full conversion power modules• Independent dc bus per converter stage to

maximize availability• Isolating grid and generator contactors • Integrated dynamic brake for LVRT• Suitable for medium speed and direct drive. • Optional generator dv/dt filters

Inherent Redundancy to maximize availability

Controls• Independent power module control

electronics. • No master controller with a single point of

failure.Benefits+ Lower bearing current stress+ Open winding failure on generator+ Hatchable converter for low MTTR

04/10/23 7

690 VGrid

PM Generator

690V

690VAC, 460 Amps

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3 Phase2.5MW 690 V

DC Bus Intertie Inverters A common approach used by commercial motor drive suppliers

- No ability to isolate inverters from the shared dc bus reduces availability.

+ Lower Cost inverter controls, switchgear, filters, power module ratings ($42k delta)

Investment Project Financial Analysis Date:Unit: DRS-PCT

Project Name: 2.5 MW Wind Converter

Investment Plan 1 2 3 4 5 6 7 8Components $420,000 $0 $0 $0 $0 $0 $0 $0

Total investment $420,000 $0 $0 $0 $0 $0 $0 $0

Revenue $0 $330,000 $330,000 $330,000 $330,000 $330,000 $330,000 $330,000Income $0 $330,000 $330,000 $330,000 $330,000 $330,000 $330,000 $330,000ROS % 100.0% 100.0% 100.0% 100.0% 100.0% 100.0% 100.0% 100.0%

Net Cash Flow ($420,000) $330,000 $330,000 $330,000 $330,000 $330,000 $330,000 $330,000

Cost of Capital 12.0%NPV $1,795,273.54 20 yrsIRR 76% 7 yrs

30MW Wind Farm Benefit with a DRS Power System

Net Present Value of Investment in Modularity. $0.8M – $1.8M: (1 to 2 failures / yr over 20 yrs)

Investment: $42k per turbine

$420k per wind farm.

Revenue: $165k per inverter event / yr

04/10/23 8

04/10/23 9

IP54

04/10/23 10

Full Power Conversion Systems for Wind Applications

• Power Module and cabinet system under development • Power modules: Grid & generator side inverters

Filters, protection, dynamic brake, controls, communications.• Generator Compatibility: PM, Synch., DFIG• Available: 500kW system in 2010

Major SpecificationsUtility Voltage: 690VOutput Capacity: 600kVA, 500kWGrid Freq: 50Hz or 60HzGenerator Freq. 10Hz to >150Hz depending on

generator requirementsCooling : Air or liquid cooled Location: Up-tower or down-tower

04/10/23 11

Ethernet Fiber

Power Converter

To 690V AC Line

Gate

drive

sig

nals

an

d

cu

rre

nt

se

nsors

Thermistor

RS

23

2

Turbine controller

CA

N

Fib

er

Op

tic lin

k

Sensing and Control

Optional Discrete I/O

DRS PEMC Embedded Control Platform

Other Sensors

Grid Side FilterGrid

Contactor

DRS Full Power Conversion Block

RouterHMI

Customer Interfacing Capability

PM GEN.

General Description

• 500kW, 690V grid connection

• PM or synchronous generators compatibility

• 1700V IGBT power converter

• Integrated dynamic brake for Low voltage ride through

• Liquid cooled power converter

• Grid contactors for protection and isolation. Generator isolation optional

• IP54 Air cooled cabinet• High reliability power

module design: high MTBF: Film capacitors, low IGBT thermal stress, liquid cooling.

04/10/23 12

DC bus capacitors

IGBTs

Gate drivers

Module Design under development

Control board

Bus plane

04/10/23 13

Wind Farm Power (MW) 30 MW Number of Turbines 10

Number of failures per month 1Duration (months) 3Lost turbine months 6Total turbine months/ yr 120% of lost turbine months 5%

Savings - if 1st turbine failure is eliminated# turbine months saved 3% turbine months saved 2.5%

Event Description

• one turbine failure per month

• Service occurs after 3 months, 3 failures

• 1st failure is assumed to be the inverter – and mitigated.

• Savings shown.