A Digital Signal Processor for Photovoltaic Generation Systems

• Main Authors: Liou, Jian-Nai, 劉鑑鼐
• Other Authors: Ma, Hsi-Pin
• Format: Others
• Language: en_US
• Published: 2013
• Online Access: http://ndltd.ncl.edu.tw/handle/49399147320019848628

碩士 === 國立清華大學 === 電機工程學系 === 101 === In reality, the operating conditions of a photovoltaic (PV) generation system are not constantly stable. The illumination of sunlight on PV panels not only changes throughout the day but also changes with the passing of clouds or shadows sometimes. In order to satisfy these dynamic operating conditions, adding a controller in a PV generation system is necessary. Traditionally, the controller in a PV generation system is realized by analog circuits. In this thesis, the controller is composed of integrated digital circuits. Compared with analog circuits, digital circuits have more flexibility and less complexity of implementing more functions on a PV generation system. The controller is programmable and is capable of executing multiple programs at high speed. Two programs are executed to control a PV generation system. One is ”modified predictive current control (MPCC)” and the other is ”maximum power point tracking (MPPT)”. Programs are modified to adapt fixed-point calculation and to shorten execution time. The final design is a dual-core processor with 100MHz clock rate on a field-programmable gate array (FPGA) platform. It is responsible for controlling a 3-channel 10-bit analog-todigital converter (A/D) with 1MHz sampling rate to obtain the required data. The main output is a 100kHz pulse-width modulation (PWM) signal with minimum precision of 0.002 duty cycle. Each core has program memory with 1KB and data memory with 256bytes. A multicore control unit is responsible for controlling communication between core to core and core to periphery. Digital pulse-width modulator (DPWM) generates a PWM signal according to the calculation results of MPCC and MPPT. The MPCC program is executed with a 2KB look-up table (LUT) memory and consumes 2.74s when operating at 100 MHz on a single core while the MPPT program consumes 2.58s 3.1s under the same conditions.