Gotowa bibliografia na temat „Utility Interactive Uninterruptible Power Converter”

This paper presents a three-phase line-interactive uninterruptible power supply (UPS) system with active series-parallel power-line conditioning capabilities. Synchronous reference frame (SRF)-based controller is used for harmonic and reactive power compensation generated from any configuration of non-linear loads. Under normal line conditions the UPS system works with universal filtering capabilities, such as compensating the input currents and output voltages. Two three-phase pulsewidth modulation (PWM) converters, called series and parallel active filters, are used to perform the series and parallel active power-line compensation. The series active filter works as sinusoidal current source in phase with the input voltage, drawing from utility sinusoidal and balanced input currents with low total harmonic distortion (THD). The parallel active filter works as sinusoidal voltage source in phase with the input voltage, providing regulated and sinusoidal output voltages with low THD. The performance of the UPS system is evaluated in three-phase, four-wire systems. Experimental results are presented to confirm the theoretical studies.

This article presents a new cascaded control strategy to control the power flow in a renewable-energy-based microgrid operating in grid-connected mode. The microgrid model is composed of an AC utility grid interfaced with a multi-functional grid interactive converter (MF-GIC) acting as a grid-forming converter, a photovoltaic (PV) power-generation system acting as grid-feeding distributed generation unit, and various sensitive/non-sensitive customer loads. The proposed control strategy consists of a fractional order PI (FO-PI) controller to smoothly regulate the power flow between the utility grid, distributed generation unit, and the customers. The proposed controller exploits the advantages of FO (Fractional Order) calculus in improving the steady-state and dynamic performance of the renewable-energy-based microgrid under various operating conditions and during system uncertainties. To tune the control parameters of the proposed controller, a recently developed evaporation-rate-based water-cycle algorithm (ERWCA) is utilized. The performance of the proposed control strategy is tested under various operating conditions to show its efficacy over the conventional controller. The result shows that the proposed controller is effective and robust in maintaining all the system parameters within limits under all operating conditions, including system uncertainties.

The increasing demand of energy over the past few years as well as the growing environmental concerns have forced the mankind to look out for non conventional sources of energy such as solar, wind etc. Consequently a large number of these energy resources are integrated to the existing power grid in a distributive manner. These resources known as distributed energy resources (DERs) are interfaced to the grid through power electronic converters. More and more DERs are being integrated to the grid. The increased penetration of DERs interfaced through power electronic converters have led to the concept of microgrids. The installation of microgrids have become a common scenario across the globe. However, the microgrid is also not devoid of technical issues like any other system. In this thesis, the author looks at some of the persistent issues in the microgrid and proposes some relevant practical solutions. The thesis is broadly divided into four parts. The first part deals with the concept of a Utility Interactive Uninterruptible Power Converter (UIUPC) and its role in a microgrid. In the first part, a new UIUPC, making use of a concept known as unified control is proposed. The proposed unified control is based on controlling the perturbations in the magnitude and speed of the point of common coupling (PCC) space vector with respect to a reference space vector applied continuously along the direction of the PCC space vector. The proposed unified control based UIUPC inherently transfers from a grid follower to a grid former and vice -versa according to the modes without the help of any islanding detection algorithms or external synchronising mechanisms. The second part of the thesis looks at the issue of communication between power converters connected in a microgrid. The thesis proposes a novel method of inter converter communication through the existing power line. The proposed method is based on the concept of using a fractional harmonic space vector to carry the data. The data is modulated and demodulated in the corresponding fractional harmonic d-q domains. The use of fractional harmonic d-q domains make the data appear as bits like a conventional communication system. The proposed method thus puts forth an inter converter communication technique which is economical and at the same time carries forward the advantages of a traditional communication system. The third part of thesis proposes a control architecture for managing a number of power converters connected in parallel in a microgrid. The proposal divides the microgrids into smaller units called cells. Each cell is made up of unified control based UIUPCs called as adaptable converters and current controlled converters. The adaptable converters ensure a smooth transition of the cell from a grid connected mode to an autonomous mode and vice versa without any interruption or breakage. The issue of energy imbalance persistent in a microgrid is also taken care of by using the inter inverter communication technique proposed. The proposed control architecture also takes care of the feature of redundancy of adaptable converters. This assures that the system remains functional in the event of a failure of the determining adaptable converters. The final part of the thesis is about the hardware implementation of the whole thesis. As a contribution towards the thesis, in this part the author introduces a new generation power converter which can be used in future. This part of the thesis also puts forward a novel integrated gate driver card. The proposed gate driver is based on interleaving of two forward converters. The proposed gate driver achieves the objectives of magnetic isolation and a wide duty cycle band along with the other necessary requirements of a gate driver card.

DC-DC power converters are necessary to step-up the voltage or current with high conversion ratio for many applications e.g. photovoltaic and fuel cell energy conversion, uninterruptible power supply, DC microgrid, automobile, high intensity discharged lamp ballast, hybrid vehicle, etc. in order to use low voltage sources. In this project, a modified SIBC (mSIBC) is proposed with reduced voltage stress across active switches. The proposed mSIBC configuration is transformerless and simply derived by replacing one diode of the classical switched inductor structure with an active switch. As a result, mSIBC required low voltage rating active switches, as the total output voltage is shared between two active switches. Moreover, the proposed mSIBC is low in cost, provides higher efficiency and required the same number of components compared to the classical SIBC. The experimental results are presented which validated the theoretical analysis and functionality, and the efficiency of the designed converter is 97.17%. The proposed mSIBC converter provides higher voltage conversion ratio compared to classical converters e.g. boost, buck-boost, cuk, and SEPIC. The newly designed configurations will aid the intermediate power stage between the renewable sources and utility grid or high voltage DC or AC load. Since, the total output voltage is distributed among the two active switches, low voltage rating switches can be employed to design the power circuit of the proposed converter. The classical boost converter or recently proposed switched inductor based boost converter can be replaced by the proposed mSIBC converter in real-time applications such as DC microgrid, DC-DC charger, battery backup system, UPS, EV, an electric utility grid. The proposed power circuitry is cost effective, compact in size, easily diagnostic, highly efficient and reliable.