Multiport power electronics circuitry for integration of renewable energy sources in low power applications : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Electrical Engineering at Massey University, Palmerston North, New Zealand

The increasing demand for electricity and the global concern about environment has led energy planners and developers to explore and develop clean energy sources. Under such circumstances, renewable energy sources (RES) have emerged as an alternative source of energy generation. Immense development has been made in renewable energy fields and methods to harvest it. To replace conventional generation system, these renewable energy sources must be sustainable, reliable, stable, and efficient. But these sources have their own distinguished characteristics. Due to sporadic nature of renewable energy sources, the uninterrupted power availability cannot be guaranteed. Handling and integration of such diversified power sources is not a trivial process. It requires high degree of efficiency in power extraction, transformation, and utilization. These objectives can only be achieved with the use of highly efficient, reliable, secure and cost-effective power electronics interface. Power electronics devices have made tremendous developments in the recent past. Numerous single and multi-port converter topologies have been developed for processing and delivering the renewable energy. Various multiport converter topologies have been presented to integrate RES, however some limitations have been identified in these topologies in terms of efficiency, reliability, component count and size. Therefore, further research is required to develop a multiport interface and to address the highlighted issues. In this work, a multi-port power electronics circuitry for integration of multiple renewable energy sources is developed. The proposed circuitry assimilates different renewable sources to power up the load with different voltage levels while maintaining high power transfer efficiency and reliability with a simple and reliable control scheme. This research work presents a new multiport non-isolated DC-DC buck converter. The new topology accommodates two different energy sources at the input to power up a variable load. The power sources can be employed independently and concurrently. The converter also has a bidirectional port which houses a storage device like battery to store the surplus energy under light load conditions and can serve as an input source in case of absence of energy sources. The new presented circuitry is analytically examined to validate its effectiveness for multiport interface. System parameters are defined and the design of different components used, is presented. After successful mathematical interpretation, a simulation platform is developed in MATLAB/Simscape to conduct simulations studies to verify analytical results and to carry out stability analysis. In the final stage, a low power, low voltage prototype model is developed to authenticate the results obtained in simulation studies. The converter is tested under different operating modes and variable source and load conditions. The simulation and experimental results are compiled in terms of converter’s efficiency, reliability, stability. The results are presented to prove the presented topology as a highly reliable, stable and efficient multiport interface, with small size and minimum number of components, for integration of renewable energy sources

The Application of Model Predictive Control on Paralleled Converters for Zero Sequence Current Suppression and Active Thermal Management

In the field of power electronics, the control of rectifiers is a crucial area of study. Rectifiers are used to convert AC power into DC power, and are commonly used in a wide range of applications, including renewable energy systems, industrial automation, and consumer electronics. However, in medium and high-power systems when multiple rectifiers are connected in parallel to a DC bus, stability issues can arise, including voltage fluctuations, zero sequence circulating current, and thermal imbalance. Achieving stable DC bus voltage is essential for maintaining the proper functioning of electronic devices, while suppressing zero sequence current is necessary for protecting the power electronics equipment from damage and ensuring that a power system\u27s performance is not degraded. Active thermal management is important for ensuring the longevity and reliability of the power electronics equipment. To achieve these objectives, advanced control techniques must be developed and implemented. This research investigates the use model predictive control to achieve three objectives in two paralleled rectifier each control cycle: DC voltage stability, zero sequence suppression, and thermal balance. These objectives are critical for ensuring the reliable and efficient operation of power electronics systems. The findings of this research will contribute to the development of more reliable and efficient power electronics systems, with the Navy\u27s (power electronic building block) PEBB systems particularly in mind. However, this research can be extended to other medium and high-powered applications in modern technology too such as missile defense systems, data centers, and uninterruptible power supplies

Characterization of Transient Heating in Power Electronic Devices and its Implications for Die Attached Reliability

Military and commercial interest in the use of power electronics for applications requiring extreme operating conditions and/or placement in extreme environments is driving research to identify and develop packaging technologies that can withstand these conditions. Specifically, there is an interest in the development of packaging technology than can function reliably under transient high power loading conditions. This thesis addresses the unique packaging considerations required for this type of application, with a focus on the implications on the durability of the die attach layer. Simulations of the thermal conditions experienced at the die attach layer for different power pulse magnitudes and durations are presented. A test apparatus and experimental test plan for studying the reliability of die attach materials under high power transient loading is discussed. Studies conducted to validate the test apparatus and characterize die attach reliability are described along with recommendations for further investigation of the reliability issues associated with high power, transient loading conditions

Comprehensive Modeling and Experimental Testing of Fault Detection and Management of a Nonredundant Fault-Tolerant VSI

This paper presents an investigation and a comprehensive analysis on fault operations in a conventional three-phase voltage source inverter. After an introductory section dealing with power converter reliability and fault analysis issues in power electronics, a generalized switching function accounting for both healthy and faulty conditions and an easy and feasible method to embed fault diagnosis and reconfiguration within the control algorithm are introduced. The proposed system has simple and compact implementation. Experimental results operating both at open- and closed-loop current control, obtained using a test bench realized using a dSPACE system and the fault-tolerant inverter prototype demonstrate that the proposed solution is effective and feasible and makes all faults easily managed by the controller itself

Impact of Gamma Radiation on Dynamic RDSON Characteristics in AlGaN/GaN Power HEMTs

GaN high-electron-mobility transistors (HEMTs) are promising next-generation devices in the power electronics field which can coexist with silicon semiconductors, mainly in some radiation-intensive environments, such as power space converters, where high frequencies and voltages are also needed. Its wide band gap (WBG), large breakdown electric field, and thermal stability improve actual silicon performances. However, at the moment, GaN HEMT technology suffers from some reliability issues, one of the more relevant of which is the dynamic on-state resistance (RON_dyn) regarding power switching converter applications. In this study, we focused on the drain-to-source on-resistance (RDSON) characteristics under 60Co gamma radiation of two different commercial power GaN HEMT structures. Different bias conditions were applied to both structures during irradiation and some static measurements, such as threshold voltage and leakage currents, were performed. Additionally, dynamic resistance was measured to obtain practical information about device trapping under radiation during switching mode, and how trapping in the device is affected by gamma radiation. The experimental results showed a high dependence on the HEMT structure and the bias condition applied during irradiation. Specifically, a free current collapse structure showed great stability until 3.7 Mrad(Si), unlike the other structure tested, which showed high degradation of the parameters measured. The changes were demonstrated to be due to trapping effects generated or enhanced by gamma radiation. These new results obtained about RON_dyn will help elucidate trap behaviors in switching transistors

Power Quality Improvement Using Distribution Static Compensator (D-Statcom) On 11 Kv Distribution System

Tile increased awareness ill power quality issues has brought tremendous changes and improvements in power electronics devices. Various circuit topologies and control techniques have been developed aimed at mitigating power quality disturbances.Custom Power concept is one of technological responses to the poor power quality presently surfacing in factories, offices and homes. It is dedicated to maintaining and improving the quality and reliability of distribution level power and to protecting customers against disturbances generated by other users in the network. Custom Power (CP) family includes power electronics based devices such as Distribution Static Compensator (D-STATCOM), Dynamic Voltage Restorer (DVR), Solid State Fault CUlTent Limiter (SSFCL), Active Power Filter (APF) and Solid State Transfer Switch (SSTS). The CP concept is the customer's solution by the utilities sector.In this research work, the focus will be on one of the CP family, that is, the D-STATCOM. The D-STATCOM, which consists of a thyristor-based voltage source inverter, uses advanced power electronics to provide voltage stabilization, power factor correction, harmonic control and a host of other power quality solutions for both utility and industrial applications. This thesis describes the configuration, design and control of the 12-pulse 0- STATCOM. Its simulation works are done by using PSCAD/EMTDC version 3.0.7 software, developed by Manitoba HVDC Research Center, Canada. The designed 0- STATCOM is connected in shunt to an 11 k V test distribution system Simulations have been carried out to illustrate the effectiveness of the D-STATCOM in mitigating voltage sags and voltage unbalance as well as eliminating harmonics. The results obtained from the simulations clearly showed that the designed D-ST ATCOM is capable in mitigating voltage sags and voltage unbalance. Furthermore, by connecting passive filters in shunt at the primary side of the step-down transformer reduces the harmonics generated by the D-STATCOM

Test Solution for Heatsinks in Power Electronics Applications

Power electronics technology is widely used in several areas, such as in the railways, automotive, electric vehicles, and renewable energy sectors. Some of these applications are safety critical, e.g., in the automotive domain. The heat produced by power devices must be eciently dissipated to allow them to work within their operational thermal limits. Moreover, numerous ageing eects are due to thermal stress, which causes mechanical issues. Therefore, the reliability of a circuit depends on its dissipation system, even if it consists of a simple passive heatsink mounted on the power device. During the Printed Circuit Board (PCB) production, an incorrect assembly of the heatsink can cause a worse heat dissipation with a significant increase of the junction temperatures (Tj). In this paper, three possible test strategies are compared for testing the correct assembling of heatsinks. The considered strategies are used at the PCB end-manufacturing. The eectiveness of the dierent test methods considered is assessed on a case study corresponding to a Power Supply Unit (PSU)

Comprehensive study of finite control set model predictive control algorithms for power converter control in microgrids

© 2020 Institution of Engineering and Technology. All rights reserved. Advances in power electronics and digital control open a new horizon in the control of power converters. Particularly, model predictive control has been developed for control applications in industrial electronics and power systems. This study presents a comprehensive study on recent achievements of model predictive control algorithms to overcome the challenges in the real-time implementation of power converter control, which is the lowest level control of hierarchical control in microgrids. The study shows that most of these alternate solutions can enhance system reliability, stability, and efficiency. The control platform devices for the real-time implementation of these algorithms are compared. The related issues are discussed and classified, respectively. Finally, a summary is provided, leading to some further research questions and future work