Lafayette Photovoltaic Research and Development System

Energy Transfer Subsystem

Final Presentation

May 11, 2009

Lafayette College-ECE Dept.

LPRDS –

ETS 2009

Project OverviewProject Overview

Total investment of $40,000 in solar infrastructure to support student projectsOne semester team-based capstone senior design project

22 student team$4000 Budget (Not including Array cost and initial battery cost)Subject to a 55 page requirements document

Technical Specifications National Electric Code (NEC) Article 690 on PV systemsReporting requirements (e.g. website, PDR reports, CDR reports, etc.)General Project Requirements (Maintainability, Sustainability, Reliability, etc.)Total of 104 requirements

Presentation Outline1. Project Overview2. ->System Input – Solar Energy3. System level design4. Subsystem design

1. RPI2. ESS3. EDS4. SCADA

5. Conclusion

Why solar energy?Energy Consumption

Energy Consumption on the riseCauses: Population growth and technological developments

Energy SourcesNon-renewable resources such as Petroleum, Natural Gas, and Coal account for 85% of US energy consumption.Solar energy accounts for less than 0.5% of total consumption. Why?

Economic Analysis – A household system is not economical for Easton, PA

A 20yr system has been calculated to cost $72,4005.45 times cost of buying from the gridTechnology will continue to improveExperts predict solar will play a role in the future energy market Cash Flow analysis (ES225)

System Input –

Solar Energy10 GEPBp-200-MS modules connected in series configuration.5 degree tilt because of wind loading.Average of 4 kwh/m2/dayWe calculated an expected power of our system 4.2kwh/day

Insolation Curve IV Curve Provided by GE

Presentation Outline1. Project Overview2. System Input – Solar Energy3. ->System level design4. Subsystem design

1. RPI2. ESS3. EDS4. SCADA

5. Conclusion

Main RequirementsAccept high voltage DC from the PhotoVoltaic Array.Output AC voltage @ 120 volts, 60Hz +/-0.05%.Total Harmonic Distortion <= 3%An Energy Storage SystemAutonomous Safety InterfaceSCADA (monitoring, control and display)

Summary of Project AccomplishmentsNumber of requirements satisfied = 100% requirements satisfied = 96.15% (note to senior management, that’s an A)

Major Requirements that were met1) AC output at 120 volts RMS 2) Energy Storage System3) Accepts DC high voltage from Photovoltaics4) Autonomous Safety Interface

Requirements Missed1) AC output at 60Hz +/- 0.05%

2) THD <= 3%3) Load Regulation <= 3%4) Transient Response <= 5%

Manufacturability1) Mean Time To Repair less than 1 week2) Spare parts in storage as order time is about 2

weeks.3) System Tolerances

SustainabilityEconomic sustainability considered for a household PV systemKey components such as PVs and batteries considered for sustainability

Ethical Considerations Kant’s Categorical Imperative

Maintainability1) MIL-HDBK-472(Note 1) and MIL-STD-470B 2) gives a MTTR of 2.6 days

Reliability1) MIL-HDBK-217 delivers MTBF of 1071 hrs. (1000 hr.

requirements)

The ‘illities’

Design Tools and FeaturesTools used:

VTBSimulink (ECE433)PSpice (ECE323)AVR studio (ECE212)Linux (CS classes)PHP MySQLC++ (CS205)C (ECE212)PADS DxDesigner (ECE323)Quick Circuit Milling Machine

Features:Commercial off the self (COTS)

Sensors (current, temperature, voltage)RelaysPICMicrocontrollerPC

Custom circuit design7 PCB boardssoftware

Safety ConcernsSafety was an integral part of the design process

Safety LectureSafety plan (signed by all students)Commercial GFISafety circuitHigh voltage/ low voltage isolation in all subsystems

System Design Supervisory Control and Data Acquisition

Monitors the system for safety issuesControls the system states

Raw Power InterfaceGround fault protection

Energy Delivery Sub-SystemProvides proper load to the batteriesDC/AC conversion (Inverter)

Energy Storage Sub-System64 LiFePO4 Cells205 Nominal Array Voltage10 Ah leads to 2.35 kWh

State Transition Diagram

Presentation Outline1. Project Overview2. System Input – Solar Energy3. System level design4. ->Subsystem design

1. ->RPI2. ESS3. EDS4. SCADA

5. Conclusion

Raw Power InterfaceMain Requirements:

Disconnect from PVGround Fault DetectionProvide Sensor Data for PV Array

RPI Exterior View

RPI Interior View

Student-Designed PIC/Sensor PCB Layout

RPI Box Layout

15A Fuse

Current Transformer

Solid-StateRelay

Output Blocks

Safety Relay

System Power

30V+ & DCIndicators

PCB with PIC

*GFMMounted on

Box Door

*Red PatternIndicates Shielded

HV Region

HVLV

RPI Features

Ground Fault Monitor- Bender RCMA420Purchase for safety concerns

Voltage, current and temperature sensorsVoltage from PV arrayVoltage to EDSCurrent sourced from PV arrayTemperature inside enclosure

PIC to perform data acquisition10-bit A/D converterRS485 serial communication

Separated into low and high voltage sides

RPI Sensor Designs

Custom Designed Sensors (Pictured):•Voltage Sensors•HV Indicator•DC Power Indicator

C.O.T.S.: Sensors:•Current Sensors•Temp. Sensors

HV Indicator Spice Simulation

RPI Summary

RPI was a complete successViable Final Version

No revisions necessary

Tested drawing power from the PV arrayCharged ESS batteries

Presentation Outline1. Project Overview2. System Input – Solar Energy3. System level design4. ->Subsystem design

1. RPI2. ->ESS3. EDS4. SCADA

5. Conclusion

Energy Storage System (ESS) Requirements

20 project requirement mapped to ESSMain requirements are listed below:

MainRequirements Specification

Pass/Fail

R002-01 Energy Accumulator is required to store excess energy Pass

R002-04 Discharge power capacity of the ESS shall be able to meet the power requirements of the system Pass

R002-06 Shutdown switch required. Pass

R002-12Containers must have closable access ports for

electrical probing of each extreme of the HV system. Pass

GPR004-20 NiCd and Lead-Acid batteries may not be used. Pass

ESS DesignParts Designed

PCB Layout (fabricated off-site)PIC codeHV (>30V) IndicatorVoltage SensorsIsolated Relay ControlPCBMetal CaseBattery Technology SelectionBattery Mounting Mechanism

Parts PurchasedDC-DC convertersRelaysDisconnect SwitchTemperature and Current Sensors

Disconnect Switch

Window andIndicator LEDs

Batteries

Steve’s Knee

Test Points

64 3.2V LiFePO4 Cells in series205V nominal @ 10 Ah = 2KW of powerUp to 70A discharge rate and 60A charge rateClever and Safe DesignWhen top is removed, there is no voltage greater than 14.8V in the battery compartmentMakes maintenance easier – individual packs can be swapped out

ESS-SchematicsFeatures:•PIC•RS485 communication to SCADA

•Indicator Lights•Voltage, Current, and TemperatureSensors

•Low Voltage sources of 5V and 12V•Relay Control

Batteries charging/discharging-

Test ResultsCharging

Discharging

1.7hrs

3.65 V

3.7 V

14.8V

0.8hrs

0.1hrs

Trickle Charging1.7hrs

0.9hrs

5A Rate

10A Rate

10A Rate

5A Rate

OVERCHARGE

3.3 V

2.75V

2.57V

3.3 V

Factory Curves

chargecycle

dischargecycle

chargecycle

ESS Photos

PIC

DisconnectSwitch

SafetyRelay

System PowerDC-DC

TemperatureSwitch

RJ45 Safety System HV I/OPower

DisconnectSwitch

TighteningPoints

Copper Plates

12.8VPack

Slot for12.8VPack

Shield

PCB Design (PADS)

ESS SummaryESS is a final part of the LPRDS-ETSFuture Additions/Changes

Voltage Ramping CircuitBattery Management System (BMS)Redesign Voltage Sensors

Presentation Outline1. Project Overview2. System Input – Solar Energy3. System level design4. ->Subsystem design

1. RPI2. ESS3. ->EDS4. SCADA

5. Conclusion

Energy Delivery System-DC to AC Converter

23 Total RequirementsMajor requirements listed below:

One PCB board fabricated in- house with 2 revisionsA copy-cat of the ESS board (fabricated off-site) for sensor valuesBudget spent- $1,020

Requirement Specification Pass/Fail

R003-02

Provide 120 V RMS AC sinusoidal at 60Hz for the load with a max sustained current of

15Amps RMS Pass

R003-0360Hz frequency is accurate to

within 0.05%. Fail

R003-04Total Harmonic Distortion is

less than 3% Fail

R003-05The system can be modified to

work at 50Hz Pass

R003-06

Load regulation is better than 3% for a 100% step load

change TBD

R003-07

Transient Response is less than 5% for a 100% step

load change. Pass

Parts designed Parts purchased

H-Bridge/Inverter Isolation Transformer

Differential Voltage measurement

12v DC-to-DC converter (hi-lo voltage isolation)

Filter microcontroller

Custom parts designed

EDS Proto board2 layout

HighCurrent Traces

EDS DesignFilter design and PWM scheme driven by THD and frequency requirementsH-Bridge design based on high voltage (120Vac) and high current (15A) requirementPossible implementation of closed loop Inverter algorithm to meet voltage regulation requirement – new power algorithm downloadableHigh and low side voltage signals required opto-isolators

H-Bridge Filter Transformer

Microcontroller

EDS –

Schematics -

1Features:•4 IGBTS •2 gate drivers •2 opto-isolators •High voltage input

goes through a16A fuse

Opto-Isolators Gate Drivers

IGBT

Fuse

EDS-

PWM Scheme

PSpice Simulation

Measured Result from Low Voltage

Prototype

Unipolar Sine PWM IGBT Drive Signals

EDS-FilterLC Filter3dB at 684.2Hz (simulated)

Simulated AC Response of Filter

EDS Board

LC Filter

Measured data from the inverter

210v DC input / 124 RMS AC at 60.5Hz50 ohm load

210v DC input / 124 RMS AC at 60.5Hz25 ohm load

1st Harmonic (60 Hz)

3rd Harmonic (180 Hz) 5th Harmonic

Interface of EDS to ESS (Batteries)Blew up!High Voltage to Low Voltage

isolation worked! High Voltage parts destroyedLow Voltage survivedSafety Plan (important)Possible cause: Current SurgeFuture Work:

Use a Start up CircuitAdditional Simulations

Presentation Outline1. Project Overview2. System Input – Solar Energy3. System level design4. ->Subsystem design

1. RPI2. ESS3. EDS4. ->SCADA

5. Conclusion

SCADA -

OverviewSupervisory Control and Data Acquisition

Monitor and log critical values in the systemProvide manual control of the systemProvide a useful interface for displaying the collected data

Major componentsHardware (Custom PCB)Software

PIC – C languagePC – C++, MYSQL, Linux OS, PHP, C

Communications protocolRS232 and RS485

SCADA -

Software Top Level Diagram

CommInterface

DatabaseDatabaseInterface

C++

Website(Graphing)

DemoApplication

Monitor

API

Input Manager

Top Level SCADA SoftwareArchitecture

To Network (Ethernet)

DatabaseInterface

(PHP)

System State Manager Inferface

(PHP)System State

Manager

The different color boxes denote different processes

SSC001 SSC002

SSC003

SSC004SSC005 SSC006

SSC007

SSC008

SSC009

SSC010

V6

PHP-MYSQL interactionMYSQL++

FilesIntraprocess calls

To SCADA PIC (232)

To S

CAD

A PI

C (2

32) SVN ver. Control (CS205)

Design principles (CS205)

Poll

Check Values

Store in database

Update System State

CommInterface

DatabaseInterface

C++

Monitor

Input Manager

System State

Manager

SSC001 SSC002

SSC003

SSC006

Database

SSC004 SSC005

SCADA -

Software Operation Overview

Give me the latest Input values

Request the latest list of inputs to check

Request latest list of inputs to poll

Request the values from the PICs

Poll

Check Values

Store in database

Update System State

SCADA -

Software Operation OverviewComm

Interface

DatabaseInterface

C++

Monitor

Input Manager

System State

Manager

SSC001 SSC002

SSC003

SSC006

Database

SSC004 SSC005

-If values not within acceptable boundaries, a fault has occurred.

-System State manager is informed.

CommInterface

DatabaseInterface

C++

Monitor

Input Manager

System State

Manager

SSC001 SSC002

SSC003

SSC006

Database

SSC004 SSC005

Poll

Check Values

Store in database

Update System State

SCADA -

Software Operation Overview

Poll

Check Values

Store in database

Update System State

SCADA -

Software Operation OverviewComm

Interface

DatabaseInterface

C++

Monitor

Input Manager

System State

Manager

SSC001 SSC002

SSC003

SSC006

Database

SSC004 SSC005

New state depends on:

• User requests

• Voltages at load and batteries

• Faults reported

SCADA Communication

RPIPCB

EDS PCB

ESSPCB

SCADAPCBPC

RS 485

RS 232 Display Board

WorldWideweb Ethernet

Ribbon Cable Connection

SCADA Sensor Communication

RPISensors

EDS Sensors

ESSSensors

PIC PIC PIC

3 Types of Sensors (Voltage, Current, and Temperature)

SCADAPCBPC

RS 485

RS 232Temp. Sensors

Linear voltage output

Voltage SensorsBuffered resistive dividersCalibrated using test data

Sensor Value = A/D value * .005v/bit * Scale factor

Current SensorsBidirectional Hall effect type

sensorCalibrated scaling factor and

offset

SCADA Board Schematic

PIC

RibbonCable Connector To DisplayBoard

Relay

SCADA Board Serial Communication Schematic

TTL

RS 232 RS 485

SCADA Board

Designed using PADs Software

Fabricated Board

SCADA –

FeaturesWebsite

URL:lprds.aec.lafayette.edu

Data historyPlotsMaintenance

picoLCD ScreenDisplay board

Presentation Outline1. Project Overview2. System Input – Solar Energy3. System level design4. Subsystem design

1. RPI2. ESS3. EDS4. SCADA

5. ->Conclusion

Engineering Management Results -Budget

Current Budget Cost $3400Andy Misc. Costs - $400

$200 under BUDGET! – enough to order food rather than cook our own.ECE Dept absorbed $4400

TOTAL ESS$763.34

23%

TOTAL SCADA$489.20

15%

SAFETY TOTAL$217.64

7%

ICD TOTAL$289.75

9% RPI TOTAL$531.51

16%

EDS TOTAL$1,028.96

30%

RPI TOTALEDS TOTALTOTAL ESSTOTAL SCADASAFETY TOTALICD TOTAL

Conclusion-ResultsTotal of 5735 project hours or $172,059 (at $30/hr)

Developed 7 UNIQUE BOARDS! (RPI, SCADA, SCADA-555, ESS, EDS-ADAPTED-ESS, EDS-PROTO1, EDS-PROTO2). Almost one for every 3 students

RPI tested and working correctlyESS tested and working correctly

Mechanical layout completeBattery management system needed

EDS with partial functionalityProto-type completed with basic functionality

SCADA with partial functionality

Conclusion –

What is next?

Buck Converter- increase power intake 12-15%Battery Current Control Algorithm –increase efficiency in storing energy in the batteries (LiFePo4 has a complicated charging curve)Grid Tie – allow us to share electricity with the gridMotor control and electric vehicles

Thanks ToDr. JemisonMr. NadovichAndy LangoussisNicolette StavrovskyDoug WoodChris Lett

Questions?