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Preliminary Design Review October 16, 2012 Christopher Corey, Josh Crowley, John Fischer, Tim Myers, Neil Severson, Kristine Thompson.

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Presentation on theme: "Preliminary Design Review October 16, 2012 Christopher Corey, Josh Crowley, John Fischer, Tim Myers, Neil Severson, Kristine Thompson."— Presentation transcript:

1 Preliminary Design Review October 16, 2012 Christopher Corey, Josh Crowley, John Fischer, Tim Myers, Neil Severson, Kristine Thompson

2 Design and implement smart microgrid energy delivery system Combine multiple/varied energy sources in most efficient use of resources possible Utilize advantages and address drawbacks of each source

3 Intelligently match energy collection to load requirement Design system to be as grid-independent as possible

4 Develop innovative system that has ability to combine sources and pursues intelligent management of sources and loads Team is varied in skill sets and fields of interests Reflected in requirements and functional roles of project

5 Rwandan Orphans Project Catch-Up School Kigali, Rwanda Provide education for 200-300 orphans and local community children Unreliable grid Primary Goals Cheap operation Robust Simple

6 Rise of renewable energy sources has increased the popularity and practicality of localized, grid-independent, and highly efficient power systems Flexible power solutions to meet needs in many settings, including developing countries

7 Increase the effectiveness and efficiency of small scale power systems System concept able to supply steady power to facilities such as schools, medical facilities, and community centers in areas of expensive and/or unreliable grid connection


9 Convert solar and grid power to single homogeneous energy carrier (DC bus) Store energy in battery system for use when resources are unavailable Delivery energy to both DC and AC loads Monitor load usage and display to user through web interface Ability to isolate system components for protection

10 Predictive load profiling System mode control by the user Optimum power point tracking for solar Weather solar resource prediction Add scalability Allow for multiple source possibilities System architecture may be followed for higher power applications Load prioritization and control


12 Functional Decomposition

13 Two control signals Variable DC output to bus/battery voltage AC constant voltage output to bus 2 Charge Controllers Bridge Rectifier Charge Controller

14 3 control signal outputs, one control input from Linux Server Load data output to Linux Server Current and voltage measurements from AC Rectifier, solar converter State of charge and load monitoring input for decision making

15 Separate in-line SCRs for load control Monitoring hardware with output to controller Specd for max draw of 55W and up to 4 loads


17 Monocrystalline Most efficient Most expensive Polycrystalline Less efficient than mono Less expensive Thin Film Lowest efficiency and density Least expensive Potentially available from University

18 Lead-acid for best emulation of large scale implementation AGM deep-cycle Maximum safety Low self-discharge Low hydrogen emission High charge rate Maintenance free Deliverable by UPS


20 Responsible for drawing and converting power from the solar panel, outputting to power bus without overcharging battery Solar Panel Solar Converter / Charge Controller Battery Variable DC Power Bus Battery Voltage DC

21 Implemented as DC-DC switching converter Buck/boost to be determined by solar panel voltages Output voltage is controlled by the power bus Set by the battery voltage This, duty cycle from controller, and converter M(D) set the PV operating point

22 Prevent overcharging of battery with charge controller Solar panel may be producing power even though battery is at max capacity Must also prevent power from flowing back into panel during times of no insolation

23 Responsible for drawing energy from grid when deemed necessary, outputting to power bus without overcharging battery AC Grid Grid Rectifier Battery 120V 60Hz AC Power Bus Battery Voltage DC

24 Implemented using a full-wave rectifier and switching (buck) regulator Will receive an input from the controller dictating whether it is in operation

25 The grid rectifier must also make sure to not overcharge the battery using a charge controller Design will be similar to the solar energy charge controller

26 System control should prevent excess power to battery, but a safety backup is needed The two charge controllers must also make sure to not exceed the maximum charge rate of the battery with their combined output currents

27 Design will keep testability in mind Allow for subcomponents to be tested on their own Ex: Converter will be capable of being tested without solar panel input or charge controller output for proper DC-DC conversion Verify small pieces of functionality individually

28 Design somewhat hinges on choice of solar panel Operating voltage range dictates converter type Currently some of most difficult / high risk components Project hinges on success of this subsystem


30 Brain of operation Central controller Controls the inputs to provide appropriate power to the loads and battery

31 Current and voltage measurements from the solar panel Current readings from the grid connection State of charge of the battery User inputs Web interface settings and readings Load monitoring measurements

32 Load control – on/off Data to the web interface Solar panel / converter control Rectifier control (on/off)

33 Calculating available power from input sources Power point tracking (PPT) for solar panel(s) Calculating required power to be delivered Controlling external hardware AC grid connection Solar converter / power point tracking Includes turning off inputs with insufficient power Reporting data to the web interface

34 Change of operation based on user mode Load priority control Use predictive models as an input for a higher efficiency system If it is going to be sunny all day, dont use the grid to charge the battery the night before If the grid is unreliable on Tuesdays, charge the battery in advance Enable optimum power point tracking when appropriate

35 Control Logic Flow

36 GPIC – General Purpose Inverter Controller National Instruments power controller board Microcontroller and custom PCB

37 General Purpose Inverter Controller Robust device for controlling grid tied and high power systems Built in FPGA Real time operating system Power protocol support

38 Advantage Simplifies a lot of implementation Disadvantage No design experience with a microcontroller Far more robust than our product needs Unit cost would be high since the GPIC is expensive

39 Advantages More design experience Board design High power considerations Choosing the right microcontroller Much more cost effective implementation Options we dont need can be eliminated Disadvantages Large added effort to the system design and implementation

40 Testing will be divided into each subsystem of control Example: power point tracking can be tested by testing a closed loop converter circuit with bench top power supply

41 There are no required parts for initial design After PCB fabrication, packages must remain the same for easy integration


43 Web interface does not require specialized software for access Enables monitoring of load power consumption Load Management (On / Off) Load profiles, for automatic power management

44 Solid State Relays Non-invasive current sensing

45 Beagle Bone Arm Cortex A8 Has a webserver pre- installed, running on the Angstrom Linux distribution. Serial UART, I2C, SPI

46 Sept 25 Initial Requirements Specification and Use Case Models Oct 16 Preliminary Design Review Present Functional Decomposition Level 0 and 1 Oct 23 Functional Decomposition Complete Functional Decomposition to Level 3 Nov 6 Proof-of-Concept Bench Testing Power Point Tracking- Optimum and Peak Switching - Converter Manipulation Apache Server for Web Interface Current Monitoring Nov 15 Demonstration of major hardware and software components and subsystems critical to major functions. Web Interface Power Point Tracking Inverter, Converters, Rectifier Dec 6 Critical Design Review (CDR) Dec 13 Proof-of-Concept Open Lab Symposium Jan 17 Final Architecture and Requirements Specification Complete Jan. 24 Detailed Design Draft Software Implementation design Order PCBs / Complete BOM Feb 7 Bench Testing of Prototype Whole System (Hardware and Software) Feb 21 Complete test analysis and report results Mar 7 Develop initial integration test plan Mar 14 Final integration test plan complete Mar 21 Complete integration testing Apr 11 Final Demonstration (EXPO) Testing Apr 25 EXPO - Demonstration for Public. May 2 Complete all technical documents

47 TaskPrimarySecondary Network InterfaceJohn FischerKit Corey Load MonitoringChristopher CoreyNone Controller H/WKristine ThompsonJohn Fischer Solar Charge ControllerJosh CrowleyKristine Thompson Rectifier Charge ControllerTim MyersNeil Severson Peak Power Point TrackingTim MyersJosh Crowley Controller S/W Architecture Neil SeversonChristopher Corey Appendix II: Division of Labor

48 Item Item Total Implement Solar 660 Load Measure and Monitor 300 Controller Implementation 568 Rectifier, Converters, and Inverter Implementation (Each) 1236 Energy Storage 230 Web Interface Implementation 120 User Interface 390 Margin300 Total 3804

49 Area of RiskContingency Plan Controller processor not robust enough to handle software scheduling requirements Controller selection will be based on robust software specification, code will be written with efficiency in mind Five boards to be developed: Scheduling constraints for system integration High cost of error Extensive prototyping combined with major development focus will ensure efficacy Subsystem implementation could prove to be infeasible These could be implemented with retail products if absolutely necessary Smart control algorithm development requires working implementation of hardware; can only be tested late in development cycle High level algorithm development is easy to scale for implementation, modeling will allow code development to begin prior to full hardware completion

50 High currents and voltages in use throughout design Each board will use over-current protection System will use breaker box to ensure modularity, provide additional protection Safe usage practices will protect group members

51 Component redundancy for critical blocks Batteries Solar panels Efficiency of individual parts determines overall system efficiency Not critical for basic goals Critical for reach goals, overall system efficacy

52 Efficiency makes up for cost of implementation in time System components will eventually fail Boards can be re-spun– no relying on manufacturer supply availability Disposability always a problem for PCBs and semiconductor materials

53 Fully utilize heterogeneous energy sources Store energy intelligently Supply power to variable loads Smart control to increase total system efficiency Adaptable to loss of individual power sources User monitoring and control

54 Most systems of this type cannot deal with multiple power sources simultaneously A new and more effective implementation of popular technology Energy independence with reliability Scalability and adaptability Use in developing countries


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