And Design And Implementation Of Network Inverter Whole SPLL

With the fast development of modern society, more and more power is needed to satisfy the energy requirement. New energy generators, such as photovoltaic (PV), are developed to supplement traditional generator. But the direct current generated by the photovoltaic technology must be changed to alternating current then incorporated into the grid by an inverter. The characterization of phase-locked loop (PLL), which can track the frequency and the phase of grid, will affect the performance of the inverter.This thesis designs three kinds of software PLL, using the digital signal processor, to overcome a variety of distortion in grid. It is organized as five chapters. Firstly, the backgrounds and prospects of PLL technology are introduced. Some kinds of traditional PLL technology and their characterization are briefly discussed. Following of those, the requirements of the software PLL (SPLL) in the current condition are introduced.The second chapter of this thesis analyzes three blocks, phase detector, loop filter, voltage control oscillator of the PLL. The mathematical models are derived to analyze the basic principle and the characteristic of the phase detector are discussed. Based on these theoretical analyses, some common loop filters are described.The structure and operation principle of the single synchronous reference frame software PLL (SSRF-SPLL) are analyzed in detail in the third chapter. The performance of the SSRF-SPLL with a variety of grid distortion conditions (such as voltage sag, imbalance voltages, etc.) are simulated using MATLAB. The simulation results are matched to the mathematical analysis.Two kinds of SPLL are designed to eliminate the negative sequence voltages. Their principles and structure diagram are given in the fourth chapter. The performances of these SPLL are analyzed using the mathematical models.Finally, the experimental platform based on digital signal Processor (DSP) is developed. The workflow and the program of the software corresponding to the three kinds of PLL are designed. The experimental results show that the theoretical analysis and simulation results are correct and feasible.