MPPT, FPGA, Perturb and Observe, Photovoltaic, Power, Satellite
Satellites need a source of power throughout their missions to help them remain operational for several years. The power supplies of these satellites, provided primarily by solar arrays, must have high efficiencies and low weights in order to meet stringent design constraints. Power conversion from these arrays is required to provide robust and reliable conversion which performs optimally in varying conditions of peak power, solar flux, and occlusion conditions. Since the role of these arrays is to deliver power, one of the principle factors in achieving maximum power output from an array is tracking and holding its maximum-power point. This point, which varies with temperature, insolation, and loading conditions, must be continuously monitored in order to react to rapid changes. Until recently, the control of maximum power point tracking (MPPT) has been implemented in microcontrollers and digital signal processors (DSPs). While DSPs can provide a reasonable performance, they do not provide the advantages that field-programmable gate arrays (FPGA) chips can potentially offer to the implementation of MPPT control. In comparison to DSP implementations, FPGAs offer lower cost implementations since the functions of various components can be integrated onto the same FPGA chip as opposed to DSPs which can perform only DSP-related computations. In addition, FPGAs can provide equivalent or higher performance with the customization potential of an ASIC. Because FPGAs can be reprogrammed at any time, repairs can be performed in-situ while the system is running thus providing a high degree of robustness. Beside robustness, this reprogrammability can provide a high level of (i) flexibility that can make upgrading an MPPT control system easy by merely updating or modifying the MPPT algorithm running on the FPGA chip, and (ii) expandability that makes expanding an FPGA-based MPPT control system to handle multi-channel control. In addition, this reprogrammability provides a level of testability that DSPs cannot match by allowing the emulation of the entire MPPT control system onto the FPGA chip. This thesis proposes an FPGA-based implementation of an MPPT control system suitable for space applications. At the core of this system, the Perturb-and-observe algorithm is used to track the maximum power point. The algorithm runs on an Alera FLEX 10K FPGA chip. Additional functional blocks, such as the ADC interface, FIR filter, dither generator, and DAC interface, needed to support the MPPT control system are integrated within the same FPGA device thus streamlining the part composition of the physical prototype used to build this control system.
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Master of Science in Electrical Engineering (M.S.E.E.)
College of Engineering and Computer Science
Electrical and Computer Engineering
Length of Campus-only Access
Masters Thesis (Open Access)
Persen, Todd, "Fpga-based Design Of A Maximum-power-point Tracking System For Space A" (2004). Electronic Theses and Dissertations. 223.