Novel anti-islanding detection method and maximum power tracking algorithm for grid connected photovoltaic systems with interleaved DC/DC converters.

摘要

Photovoltaic (PV) energy, which has proven to be environmentally friendly and sustainable compared to traditional energy sources, has gained widespread attention in recent years. The grid-tied PV energy conversion system has become a preferred choice for renewable power generation since it does not need energy storage devices. In this dissertation, an advanced state-of-the-art PV energy system is developed. This includes a high-efficiency zero-voltage zero-current switching DC/DC converter with active voltage clamping for power loss minimization, a multiphase interleaved power conversion system with cascade control for power rating expansion, a modified maximum power point tracking (MPPT) scheme with improved accuracy and dynamic response, a novel active frequency drift anti-islanding detection method with grid code compliances, and a laboratory prototype PV energy system for performance evaluation and verification.;To increase the power rating of the PV converters, a multi-channel DC/DC converter system, consisting of multiple units of parallel converters and operating in an interleaved mode, is developed. A new cascade control method is proposed, where the PV array voltage is controlled by a master converter and the active current sharing is implemented by the remaining slave converters. The performance of the new control method under varying temperature and irradiance levels are analyzed and verified by simulation in the Matlab/Simulink platform.;Various MPPT algorithms are investigated and their performance with rapid changes in irradiance and temperature are compared. A detailed simulation of the algorithms is carried out, and an experimental setup is developed.;The islanding phenomenon in renewable energy systems is examined, and an improved active anti-islanding detection method that can detect islanding with less total harmonic distortion compared to the conventional methods is proposed. The rms value and the Fourier series coefficients of the current waveform of the proposed method are obtained and used to derive the operational characteristics of the method.;Various soft switched DC/DC converters for PV applications are investigated. A new gating scheme for the converter with active voltage clamping that results in zero-voltage and zero-current switching (ZVZCS) is proposed. The operating principles of the proposed converter are presented and its performance is investigated.