Type of Document Dissertation Author Xu, Jinglin Author's Email Address firstname.lastname@example.org URN etd-03292009-221122 Title FPGA-Based Rear Time Processing of Time-Varying Waveform Distortions and Power Disturbances in Power systems Degree Doctor of Philosophy Department Electrical and Computer Engineering, Department of Advisory Committee
Advisor Name Title Uwe Meyer-Baese Committee Chair Anke Meyer-Baese Committee Member Hui Li Committee Member Juan Ordˇ˝ez Outside Committee Member Keywords
- Power Quality
- Power Systems
- Real Time
Date of Defense 2008-12-03 Availability unrestricted AbstractWaveform distortions in power systems are inherently time-varying due to continuous changes in system configurations, load types, and load levels. The time-varying nature of waveform distortions requires a real time tool to process that is essential in several applications including control, protection, and monitoring in power systems.
The traditional fast Fourier transform (FFT) is known to lost accuracy in nonstationary conditions. Some techniques for examining the time-varying nature of the waveform have been proposed in the past. But most of proposed techniques are not suitable for real time processing and practical implementations. There is still a need for developing faster, more precise and more robust algorithms with simple structure for real time processing and implementation purposes.
General-purpose programmable Digital Signal Processors (PDSPs) have enjoyed tremendous success in implementing most Digital Signal Processing (DSP) algorithm in power systems for the last two decades and work as the real time task processor in power quality monitoring systems. Field Programmable Gate Arrays (FPGAs) are becoming more and more affordable and the performance of FPGAs continues to increase. The FPGA is used in many applications as an alternative device to the PDSP. Most algorithms for power quality monitoring are digital filtering based algorithms. The FPGA is known to be more efficient than PDSP in implementing digital filtering algorithms, which makes the FPGA-based architecture an attractive option for power quality monitoring systems. In the past, very little FPGA implementation of power quality algorithms was provided.
In this dissertation, an amplitude tracking algorithm derived from universal Amplitude Demodulation (AM-Demodulation) method in telecommunications is proposed for real time tracking of time-varying waveform distortions in power systems. The proposed algorithm also works for real time tracking of power disturbances. The amplitude tracking algorithm consists of frequency mixer calculations, lowpass filtering, and coordinate transformation. The IIR (Infinite Impulse Response) filter was considered as the most efficient computation path and was selected to implement the required lowpass filtering. The COordinate Rotation DIgital Computer (CORDIC) algorithm is used for required rectangular to polar coordinate conversions. The CORDIC algorithm needs only addition and shift operations and greatly reduces the circuit complexity. The proposed algorithm has a linear computational complexity of . The propose amplitude tracking algorithm has real time characteristics of mathematical simplicity, accuracy, low latency, and robustness. Compared with the traditional FFT algorithm, one advantage of the proposed algorithm is that the proposed algorithm does not need integer periods sampled.
In this dissertation, the FPGA is introduced in the power quality monitoring for processing of real time tasks. The FPGA implementation of the proposed algorithm is presented. Appropriate choice of word length and implementation method, such as the Canonical signed digit (CSD) coding and the zero first implementation, achieves large circuit savings. The amplitude tracking circuit has been built on a Xilinx Spartan-3 XC3S200 FPGA. The real time capability of the proposed algorithm and circuit was verified through experiments.
This dissertation provides an alternative method for real time processing of time-varying waveform distortions and power disturbances in power systems. The proposed algorithm is suitable for practical implementations. This dissertation also indicates that the FPGA-based architecture could be an alternative to the traditional PDSP-based architecture of power quality monitoring systems.
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