DC-DC power converter research for Orbiter/Station power exchange

This project was to produce innovative DC-DC power converter concepts which are appropriate for the power exchange between the Orbiter and the Space Station Freedom (SSF). The new converters must interface three regulated power buses on SSF, which are at different voltages, with three fuel cell power buses on the Orbiter which can be at different voltages and should be tracked independently. Power exchange is to be bi-directional between the SSF and the Orbiter. The new converters must satisfy the above operational requirements with better weight, volume, efficiency, and reliability than is available from the present conventional technology. Two families of zero current DC-DC converters were developed and successfully adapted to this application. Most of the converters developed are new and are presented

Power Quality Enhancement in Electricity Grids with Wind Energy Using Multicell Converters and Energy Storage

In recent years, the wind power industry is experiencing a rapid growth and more wind farms with larger size wind turbines are being connected to the power system. While this contributes to the overall security of electricity supply, large-scale deployment of wind energy into the grid also presents many technical challenges. Most of these challenges are one way or another, related to the variability and intermittent nature of wind and affect the power quality of the distribution grid. Power quality relates to factors that cause variations in the voltage level and frequency as well as distortion in the voltage and current waveforms due to wind variability which produces both harmonics and inter-harmonics. The main motivation behind work is to propose a new topology of the static AC/DC/AC multicell converter to improve the power quality in grid-connected wind energy conversion systems. Serial switching cells have the ability to achieve a high power with lower-size components and improve the voltage waveforms at the input and output of the converter by increasing the number of cells. Furthermore, a battery energy storage system is included and a power management strategy is designed to ensure the continuity of power supply and consequently the autonomy of the proposed system. The simulation results are presented for a 149.2 kW wind turbine induction generator system and the results obtained demonstrate the reduced harmonics, improved transient response, and reference tracking of the voltage output of the wind energy conversion system.Peer reviewedFinal Accepted Versio

Modeling and analysis of power processing systems: Feasibility investigation and formulation of a methodology

A review is given of future power processing systems planned for the next 20 years, and the state-of-the-art of power processing design modeling and analysis techniques used to optimize power processing systems. A methodology of modeling and analysis of power processing equipment and systems has been formulated to fulfill future tradeoff studies and optimization requirements. Computer techniques were applied to simulate power processor performance and to optimize the design of power processing equipment. A program plan to systematically develop and apply the tools for power processing systems modeling and analysis is presented so that meaningful results can be obtained each year to aid the power processing system engineer and power processing equipment circuit designers in their conceptual and detail design and analysis tasks

High-performance condenser microphone with fully integrated CMOS amplifier and DC-DC voltage converter

The development of a capacitive microphone with an integrated detection circuit is described. The condenser microphone is made by micromachining of polyimide on silicon. Therefore, the structure can be realized by postprocessing on substrates containing integrated circuits (IC's), independently of the IC process, integrated microphones with excellent performances have been realized on a CMOS substrate containing dc-dc voltage converters and preamplifiers. The measured sensitivity of the integrated condenser microphone was 10 mV/Pa, and the equivalent noise level (ENL) was 27 dB(A) re. 20 ¿Pa for a power supply voltage of 1.9 V, which was measured with no bias voltage applied to the microphone. Furthermore, a back chamber of infinite volume was used in all reported measurements and simulation

Hybrid PV-Wind, Micro-Grid Development Using Quasi-Z-Source Inverter Modeling and Control—Experimental Investigation

This research work deals with the modeling and control of a hybrid photovoltaic (PV)-Wind micro-grid using Quasi Z-source inverter (QZsi). This inverter has major benefits as it provides better buck/boost characteristics, can regulate the phase angle output, has less harmonic contents, does not require the filter and has high power performance characteristics over the conventional inverter. A single ended primary inductance converter (SEPIC) module used as DC-DC switched power apparatus is employed for maximum power point tracking (MPPT) functions which provide high voltage gain throughout the process. Moreover, a modified power ratio variable step (MPRVS) based perturb & observe (P&O) method has been proposed, as part of the PV MPPT action, which forces the operating point close to the maximum power point (MPP). The proposed controller effectively correlates with the hybrid PV, Wind and battery system and provides integration of distributed generation (DG) with loads under varying operating conditions. The proposed standalone micro grid system is applicable specifically in rural places. The dSPACE real-time hardware platform has been employed to test the proposed micro grid system under varying wind speed, solar irradiation, load cutting and removing conditions etc. The experimental results based on a real-time digital platform, under dynamic conditions, justify the performance of a hybrid PV-Wind micro-grid with Quasi Z-Source inverter topology

Development of a multilevel converter topology for transformer-less connection of renewable energy systems

The global need to reduce dependence on fossil fuels for electricity production has become an ongoing research theme in the last decade. Clean energy sources (such as wind energy and solar energy) have considerable potential to reduce reliance on fossil fuels and mitigate climate change. However, wind energy is going to become more mainstream due to technological advancement and geographical availability. Therefore, various technologies exist to maximize the inherent advantages of using wind energy conversion systems (WECSs) to generate electrical power. One important technology is the power electronics interface that enables the transfer and effective control of electrical power from the renewable energy source to the grid through the filter and isolation transformer. However, the transformer is bulky, generates losses, and is also very costly. Therefore, the term "transformer-less connection" refers to eliminating a step-up transformer from the WECS, while the power conversion stage performs the conventional functions of a transformer. Existing power converter configurations for transformer-less connection of a WECS are either based on the generator-converter configuration or three-stage power converter configuration. These configurations consist of conventional multilevel converter topologies and two-stage power conversion between the generator-side converter topology and the high-order filter connected to the collection point of the wind power plant (WPP). Thus, the complexity and cost of these existing configurations are significant at higher voltage and power ratings. Therefore, a single-stage multilevel converter topology is proposed to simplify the power conversion stage of a transformer-less WECS. Furthermore, the primary design challenges – such as multiple clamping devices, multiple dc-link capacitors, and series-connected power semiconductor devices – have been mitigated by the proposed converter topology. The proposed converter topology, known as the "tapped inductor quasi-Z-source nested neutral-point-clamped (NNPC) converter," has been analyzed, and designed, and a prototype of the topology developed for experimental verification. A field-programmable gate array (FPGA)-based modulation technique and voltage balancing control technique for maintaining the clamping capacitor voltages was developed. Hence, the proposed converter topology presents a single-stage power conversion configuration. Efficiency analysis of the proposed converter topology has been studied and compared to the intermediate and grid-side converter topology of a three-stage power converter configuration. A direct current (DC) component minimization technique to minimize the dc component generated by the proposed converter topology was investigated, developed, and verified experimentally. The proposed dc component minimization technique consists of a sensing and measurement circuitry with a digital notch filter. This thesis presents a detailed and comprehensive overview of the existing power converter configurations developed for transformer-less WECS applications. Based on the developed 2 comparative benchmark factor (CBF), the merits and demerits of each power converter configuration in terms of the component counts and grid compliance have been presented. In terms of cost comparison, the three-stage power converter configuration is more cost-effective than the generatorconverter configuration. Furthermore, the cost-benefit analysis of deploying a transformer-less WECSs in a WPP is evaluated and compared with conventional WECS in a WPP based on power converter configurations and collection system. Overall, the total cost of the collection system of WPP with transformer-less WECSs is about 23% less than the total cost of WPP with conventional WECs. The derivation and theoretical analysis of the proposed five-level tapped inductor quasi-Z-source NNPC converter topology have been presented, emphasizing its operating principles, steady-state analysis, and deriving equations to calculate its inductance and capacitance values. Furthermore, the FPGA implementation of the proposed converter topology was verified experimentally with a developed prototype of the topology. The efficiency of the proposed converter topology has been evaluated by varying the switching frequency and loads. Furthermore, the proposed converter topology is more efficient than the five-level DC-DC converter with a five-level diode-clamped converter (DCC) topology under the three-stage power converter configuration. Also, the cost analysis of the proposed converter topology and the conventional converter topology shows that it is more economical to deploy the proposed converter topology at the grid side of a transformer-less WECS

Hybrid and modular multilevel converter designs for isolated HVDC–DC converters

Efficient medium and high-voltage dc-dc conversion is critical for future dc grids. This paper proposes a hybrid multilevel dc-ac converter structure that is used as the kernel of dc-dc conversion systems. Operation of the proposed dc-ac converter is suited to trapezoidal ac-voltage waveforms. Quantitative and qualitative analyses show that said trapezoidal operation reduces converter footprint, active and passive components' size, and on-state losses relative to conventional modular multilevel converters. The proposed converter is scalable to high voltages with controllable ac-voltage slope; implying tolerable dv/dt stresses on the converter transformer. Structural variations of the proposed converter with enhanced modularity and improved efficiency will be presented and discussed with regards to application in front-to-front isolated dc-dc conversion stages, and in light of said trapezoidal operation. Numerical results provide deeper insight of the presented converter designs with emphasis on system design aspects. Results obtained from a proof-of-concept 1-kW experimental test rig confirm the validity of simulation results, theoretical analyses, and simplified design equations presented in this paper. - 2013 IEEE.Scopu

A Modified High Voltage Gain Quasi-Impedance Source Coupled Inductor Multilevel Inverter for Photovoltaic Application

publishedVersio