Scalable Regulated Three Phase Power Rectifier

Transcription

1 ECE Senior Design Project Proposal For Scalable Regulated Three Phase Power Rectifier February 24, 2004 Rev. 1.0 Sponsors: Dr. Herb Hess (University of Idaho) Dr. Richard Wall (University of Idaho) Tao Nguyen Tyler Budzianowski 1

2 Table of Contents 1. Project Summary Statement of Objectives Significance of Project Methods to be Employed Project Description Objectives of the Proposed Work Characterization of Existing Three Phase Power Converter Upgraded Modified Existing Three Phase SCR Power Rectifier Significance of Project General Plan of Work (Methods and Descriptions) Review and Research MATLAB System Model System Reproduction With PIC16C73B Closed Loop Control Implementation Voltage Scalability and User Friendly Command Structure Upgrade Silicon-Controlled Rectifier (SCR) and Protection System Components and Testing Additional Considerations Component Costs Safety Identity and Role of Technical Advisor Schedule Budget Biography Bibliography.12 2

3 1. Project Summary 1.1 Statement of Objectives The objectives of the proposed project are to efficiently update hardware and software used to implement a Three Phase Silicon-Controlled Rectifier (SCR) in order to meet the specifications outlined, and to allow the design to be accurately reproduced by others seeking similar results. 1.2 Significance of Project Due to the obsolete Intel 80C196KD processor and difficulties in understanding the codes of the existing system and a desire for increased accuracy, an improved software and hardware design is necessary. New technologies have been developed to increase the accuracy and efficiency of the three-phase SCR power rectifier system that include an upgrade to a Microchip PIC microcontroller system, as well as integrating new methods for zero-crossing detection as outlined in Richard Wall s 2003 paper entitled Simple Methods for Zero Crossing Detection. These advancements will be incorporated into the existing design. 1.3 Methods to be Employed After a thorough review of the existing system design, a Matlab software model will first be developed for the entire system. The 80C196KD microcontroller and its assembler code in the existing system will then be replaced by a modern Microchip PIC series microcontroller. The upgrading of the software components will produce a more accurate zero crossing time, incorporating new zero-crossing detection technology. For upgrading the hardware components, the SCR gate firing architecture will be upgraded with more modern and commercially available firing circuitry. Designing scalability for the input voltage and output power is needed for the new system because the allowable of input voltage and output power shall be from 12VAC to 230VAC and watt to kilowatt, respectively. Finally, a local display for system information will be created in the system, so that the users are able to read the input voltage, power or current output. 2. Project Description 2.1 Objectives of Proposed Work The overall objective of the proposed project is to efficiently update hardware and software used to implement a Three Phase Silicon-Controlled Rectifier (SCR) in order to meet 3

4 the specifications outlined. The design shall be easily understood by others seeking to reproduce similar results as outlined in [1]. Because the Intel 80C196KD processor is obsolete and no longer in production, these results will be obtained using a Microchip PIC16C73B processor with an updated algorithm for zero-crossing detection Characterization of Existing Three Phase SCR Power Rectifier The existing design for a Three Phase Silicon-Controlled Rectifier consists of three main components: a microcontroller processor, optoisolator noise-filtering configuration, and SCR gate drivers. The system is driven by an Intel 80C196KD processor to ultimately provide the pulse firing that controls the SCR output voltage. A phase-locked loop (PLL) algorithm is implemented within the original processor to provide input signal frequency tracking for greater system accuracy and reliability, allowing independent signal capture and lock characteristics [2]. The signal itself is captured by means of zero-crossing detection for each phase of the input signal. New methods for zero-crossing detection have been outlined by Dr. Richard Wall that provide simplification of the detection algorithm and greater accuracy. A new processor and algorithm structure is necessary to implement these new methods and to allow for these results to be obtained for commercial applications Upgraded and Modified Three Phase SCR Power Rectifier Design The new system will be designed to meet the following specifications: System reproduction with a modern PIC series microcontroller. Implementation of closed-loop control for voltage and current regulation. Scalability design for inputs from 12 VAC to 230 VAC and output power ranging from watts to hundreds of kilowatts. The prototype should use less than 25VAC. Installation of a user-friendly voltage input command structure using a serial bus architecture. Creation of a local display for system information such as voltage input and power or load current output. Upgrade of the zero-crossing detection instrumentation to conform to new technology. 4

5 Upgrade of the SCR gate firing architecture. Use of commercially available firing circuitry is encouraged. Installation of reasonable snubbing and protection for SCRs. 2.2 Significance of the project In 1996 Richard Wall and Herb Hess authored a paper titled, Design and Microcontroller Implementation of a Three Phase SCR Power Rectifier. Essentially a scalable rectifier was designed to utilize zero-crossing detection and phase-locked-loop technology to produce a scaled and regulated voltage output by means of an Intel 87C196KD-20 embedded microcontroller. Unfortunately, the microprocessor 80C196KD is now no longer in production, and others seeking to reproduce the design respond that the code in the existing system is difficult to understand and transfer to their specific application. However, new technologies have been developed to increase the accuracy and efficiency of Microcontroller Implementation of a Three Phase SCR Power Rectifier System. These newer technologies include an upgrade to the hardware components and the PIC microcontroller system, as well as new methods for zerocrossing detection as outlined by Richard Wall. 2.3 General Plan of Work Review and Research The existing system will be reviewed and investigated thoroughly as to how the overall system functions, ease of usability, as well as what necessary components are included and how each can be upgraded for efficiency and accuracy. Because the existing design is extensive and utilizes several crucial components, care must be taken to ensure that all changes made are absolutely advantageous and easily understood by others MATLAB System Model A model will be developed to effectively simulate and analyze the entire rectification system. A main emphasis of this model will be with the phase-locked-loop control system to ensure accurate phase lock (Figure 4 of [3]), zero crossing detection, and silicon-controlled rectifier pulse firing timing (Figure 6 of [3]). Because there can be error associated with these algorithms, a model will be essential in detecting such errors and minimizing them System Reproduction with PIC16C73B 5

6 The 80C196KD processor used in the original design and implementation will be replaced with the PIC16C73B processor. This requires updating and transferring the existing phase-locked-loop algorithm and incorporating new zero-crossing detection methods. The PIC16C73B has sufficient memory (4K word program memory and 192 byte random access memory) to meet the computing requirements of the original design plus the new zero-crossing detection system [3] Closed Loop Control Implementation The existing rectifier design utilizes only open-loop voltage control. Therefore, the accuracy of zero-crossing detection and silicon-controlled rectifier pulse firing timing can be increased by implementing a closed-loop control system that has the ability to correct inaccuracies within measurements. The closed loop control system in this application will provide efficient voltage and current regulation for the system and can assist in system safety and protection Voltage Scalability and User Friendly Command Structure An important feature of the rectification system is voltage scalability such that an input voltage can vary anywhere from 12 VAC to 230 VAC. This scalability will be selectable based on an easy to use system interface that utilizes a serial bus architecture and display. Because the existing system employs simple up/down push button switches to control scalability, the PIC16C73B-contolled system will make use of a more accurate and easy-to-use system such as a display for voltage input and load power/current output in conjunction with a keypad Upgrade of Silicon-Controlled Rectifiers (SCR) and Protection The SCR gate firing architecture will be upgraded by using commercially available firing circuitry. The upgraded system will utilize a reasonable snubbing and protection system to protect the rectifier thyristors in the circuit from voltage/current overload at system turn-on and turn-off points as well as to ensure that voltage and current waveforms are not high simultaneously [4]. 6

7 2.3.7 System Components and Testing The upgraded system incorporating all of the features outlined above will be constructed with the obtained components and materials on a circuit board format and will be simulated and analyzed for accuracy and precision. All design aspects will be essentially tested to ensure that the system meets all of the requirements and specifications requested, and can be easily reproduced. 2.4 Additional Considerations Component Costs The existing design can be reproduced using components totaling a cost of under $50 (US). An upgraded design will also use low-cost components and can achieve a similar low overall cost. This will allow for straightforward reproduction of the upgraded design by others to meet one of the main project specifications Safety The Three Phase Rectifier System is designed to handle relatively high voltages on the input and the output sides of the device and safety is therefore an important concern for the design. The safety of the components as well as the safety of the operator will be a priority for the device. Component and circuitry protection will be handled by the protection and snubbing system previously described, while personal safety will involve a grounding system to ensure that should unstable voltages/currents or other system parameters and malfunctions occur, such instabilities do not become lethal to the user. 2.5 Technical Advisors The primary technical advisors and sponsors for the Three Phase SCR system will be Dr. Herb Hess and Dr. Richard Wall from the Electrical and Computer Engineering Department at the University of Idaho in Moscow, Idaho. Dr. Hess and Dr. Wall have substantial and thorough knowledge of the existing system design and have outlined the specifications and requirements as previously described. 7

8 3. Schedule Table. 1 Time schedule for Project Methods March 2003 April 2003 May 2003 Review and Research Matlab System Model Design and PIC16C73B Implementation Close Loop Control Implementation Voltage Scalability and User Friendly Command Structure Upgrade SCR and Install Protection Testing xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx xxxxxxxxxxxxxxxxxxxxxxxx xxxxxxxxxxxxxx Table. 2 Time schedule continue for Project Methods Sept 2004 Oct 2004 Nov 2004 Dec 2004 Review and Research PIC16C73B Implementation Close Loop Control Implementation Voltage Scalability and User Friendly Command Structure Upgrade SCR and Install Protection Testing xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx xxxxxxxxxxxxxxxxxxx xxxxxxxxxxxxxxxxxxx xxxxxxxxxxxxxxxxxxx xxxxxxxxxxxxx xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx All work will be divided equally between two team members, Tao Nguyen and Tyler Budzianowski. 8

9 4. Budget All costs showed in the below table are in U.S. dollars Table 2. Budget details for the Project Labor Costs: Tyler Budzianowski (165 hrs - $25/hr) $4,200 Tao Nguyen (165hrs - $25/hr) $4,200 Equipment Costs: 6 Thyristors $ PIC16C73B processor $ TLP2200 Optoisolators $22.50 Buttons/Keypad $30.00 Display $ SCR Gate Drivers $10.00 Total Costs: $8510 9

10 5. Biography Tyler M. Budzianowski 515 Almon St. Apt. B Moscow, ID, budz6104@uidaho.edu Education Senior Electrical Engineering Undergraduate Student, University of Idaho Graduation Data: Fall 2004 Experience Digital Logic Circuit (EE 244, spring 2002): Designed and implemented digital logic circuit to operate a finite state machine that governs the control of a four-way sensing stoplight system. The project involved a full design process, from state table/diagram, Karnaugh mapping, logic circuit design, to final implementation and experimentation. Package Sorter System (ENGR 211, spring 2002): Designed and analyzed a various weight and size package sorter system in a group environment to Increase efficiency of parcel distribution companies. Relevant Coursework Electronics I, II Power Electronic Circuits Active Filter Design Microcontrollers Signals and Systems Analysis Technical Writing 10

11 Tao Nguyen 318 W. Sixth Street Moscow, ID, Education Senior Electrical Engineering Undergraduate Student, University of Idaho Graduation Data: Fall 2004 Experience Spring 2002 Digital and Logic Design Project Design a digital circuit for a car race detector, circuit able to output the first, second and third winner. The outputs showed by the Lighting Emitting Diodes. Relevant Coursework Electronics I, II Power Electronic Circuits Microcontrollers Signals and Systems Analysis Electromagnetic wave Technical Writing 11

12 6. Bibliography [1]. Wall, R. W., and H.L. Hess (2003). Proposed Senior Design Project for ECE 480/482 Spring Semester [2] Wall, R. W., and H.L. Hess, (1996). Design of Microcontroller Implementation of a Three SCR Power Converter. In Journal of Circuits, Systems, and Computers, Vol. 6, No. 6, March, pp Methods for Detecting [3] Wall, R. W., (2003). Simple Method for Detecting Zero Crossing. In IEEE IECON 03, Roanoke, Virginia, November 2-6, pp [4] Mohan, N., T. Undeland, and W. Robbins, (2003). Power Electronics: Converters, Applications, and Design. Second Edition. (pp ) New York: Willey 12