Novel Anti-Islanding Detection Method And Maximum Power Tracking Algorithm For Grid Connected Photovoltaic Systems With Interleaved DC/DC Converters

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 stateof-the-art PV energy system is developed. This includes a high-efficiency zero-voltage zerocurrent 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 met hod with grid code compliances, and a laboratory prototype PV energy system for performance evaluation and verification. 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 zerocurrent switching (ZVZCS) is proposed. The operating principles of the proposed converter are presented and its performance is investigated. 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.

Novel Anti-Islanding Detection Method And Maximum Power Tracking Algorithm For Grid Connected Photovoltaic Systems With Interleaved DC/DC Converters

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 stateof-the-art PV energy system is developed. This includes a high-efficiency zero-voltage zerocurrent 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 met hod with grid code compliances, and a laboratory prototype PV energy system for performance evaluation and verification. 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 zerocurrent switching (ZVZCS) is proposed. The operating principles of the proposed converter are presented and its performance is investigated. 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.

Design of a Robust ESD Protection Device using 6H-SiC Nano-Scale GGNMOS

With the continuous shrinking of the technological nodes and the introduction of new device concepts and materials, integrated circuits (IC) are becoming more vulnerable to electrostatic discharge (ESD) induced failures which is one of the major concerns in designing robust ICs. Therefore, to improve the reliability of the ICs against ESD induced failures, extensive research efforts are being conducted. In this paper, we have presented a 6H-SiC based nano-scale grounded-gate NMOS (ggNMOS) ESD protection device and compared the results with the 3C-SiC-based ggNMOS. To design a robust ESD protection device, some critical device parameters, such as substrate doping concentration, source/drain doping concentration, drain to substrate contact spacing, and substrate contact resistance should be optimized. The ESD protection characteristics can be improved by utilizing the near punch-through effect. It was found that the trigger voltage and hold voltage are higher in 6H-SiC than the 3C-SiC having identical device parameters. 6H-SiC shows better voltage clamping performance as the turn-on resistance of 6H-SiC is smaller compared to the 3C-SiC material. Therefore, the results show that 6H-SiC has a better performance compared to 3C-SiC and due to its higher bandgap, and can be used as a good ESD protection device. All the simulations are carried out using the Silvaco ATLAS device simulator.