Index to 1984 NASA Tech Briefs, volume 9, numbers 1-4

Short announcements of new technology derived from the R&D activities of NASA are presented. These briefs emphasize information considered likely to be transferrable across industrial, regional, or disciplinary lines and are issued to encourage commercial application. This index for 1984 Tech B Briefs contains abstracts and four indexes: subject, personal author, originating center, and Tech Brief Number. The following areas are covered: electronic components and circuits, electronic systems, physical sciences, materials, life sciences, mechanics, machinery, fabrication technology, and mathematics and information sciences

Communications techniques and equipment: A compilation

This Compilation is devoted to equipment and techniques in the field of communications. It contains three sections. One section is on telemetry, including articles on radar and antennas. The second section describes techniques and equipment for coding and handling data. The third and final section includes descriptions of amplifiers, receivers, and other communications subsystems

Performance and Loss Analysis of Squirrel Cage Induction Machine Based Flywheel Energy Storage System

Flywheel energy storage systems (FESS) are one of the earliest forms of energy storage technologies with several benefits of long service time, high power density, low maintenance, and insensitivity to environmental conditions being important areas of research in recent years. This paper focusses on the electrical machine and power electronics, an important part of a flywheel system, the electrical machine rotating with the flywheel inertia in order to perform charge-discharge cycles. The type of machine used in the electrical drive plays an important role in the characteristics governing electrical losses as well as standby losses. Permanent magnet synchronous machine (PMSM) and induction machines (IM) are the two most common types of electric machines used in FESS applications where the latter has negligible standby losses due to its lower rotor magnetic field until energised by the stator. This paper describes research in which the operational and standby losses of a squirrel-cage induction machine-based flywheel storage system (SCIM-FESS) are modelled as a system developed in MATLAB/Simulink environment inclusive of the control system for the power electronics converters. Using the proposed control algorithm and in-depth analysis of the system losses, a detailed assessment of the dynamic performance of the SCIM-FESS is performed for different states of charging, discharging, and standby modes. The results of the analysis show that, in presence of system losses including aerodynamic and bearing friction losses, the SCIM-FESS has satisfactory characteristics in energy regulation and dynamic response during load torque variations. The compliance of FESS and its conversion between the generating and motoring mode within milliseconds show the responsiveness of the proposed control system

A Doubly-Fed Induction Generator (DFIG)-Based Wind-Power System with Integrated Energy Storage for Remote Electrification

Electrification of off-grid remote communities is commonly accomplished through diesel generators. The method may even be employed in cases where there exists an un­ reliable connection to the power grid. Regardless, the method is environmentally-hostile, typically costly, and likely risky. Therefore, to mitigate the reliance on diesel fuel, uti­ lization of renewable energy resources has been considered in recent years. This thesis investigates the feasibility of and technical considerations involved in the employment of a specific class of variable-speed wind-power systems, integrated with battery energy stor­ age, for remote electrification applications. The wind-power system under consideration is based on the doubly-fed induction gen­ erator (DFIG) technology, which features a number of characteristics that render it at­ tractive for the incorporation of battery energy storage. This thesis identifies the control strategy, different control sub-functions, and the controllers structures/parametes required to accommodate the battery energy storage. The developed control strategy enables the operation of the wind-power/storage system in the off-grid (islanded) mode of operation, as well as the grid-connected mode of operation. Under the developed control strategy, the wind-power/storage system can operate in parallel with constant-speed wind-power units, passive loads, and induction motor loads. The effectiveness of the proposed control strategy has been demonstrated through comprehensive simulation studies enabled by the commercial software package PSCAD/EMTDC. In addition to the control aspects, this thesis studies the reliability aspects of the pro­ posed wind-power/storage system, for an example remote electrification system. Thus, a new reliability assessment method has been developed in this thesis, which combines the existing analytical and simulation-based probabilistic approaches. The reliability analysis conducted indicates that the battery energy storage capacity, the wind magnitude and pro­ file, and the load profile impose remarkable impacts on the reliability of the electrification system. It also indicates that a connection to the power grid, however unreliable, signifi­ cantly mitigates the need for a large battery to achieve a given degree of reliability

Development of a System for Testing Grid-connected Doubly Fed Induction Generators with Implementation of a Three-level Neutral-Point-clamped Converter

Consistent international efforts have been made over the past few decades to move the world towards an environmentally sustainable society. Wind energy conversion systems (WECSs) are one of the largest contributors within this movement. Furthermore amongst existing wind turbine power generation technologies, the doubly fed induction generator (DFIG) has been distinctively popular for its lower capital costs especially in higher power applications. In order to study the integration of this type of generator into the grid, a laboratory based DFIG test rig was developed where its complete design process is presented in this dissertation. Mathematical modelling of related system components were thoroughly investigated so as to facilitate controller design based on the internal model control (IMC) methodology. In addition, a complete soft grid synchronisation procedure for the DFIG was investigated. It was found that the application of active damping within the IMC control law resulted in reduced stator current transients during synchronisation. Control voltage excitation for the DFIG rotor circuit was achieved by the implementation of two voltage source converters (VSC’s) connected in a back-to-back configuration via a common DC-link. The rotorside converter (RSC) was responsible for regulating the machine speed whereas the grid-side converter (GSC) was responsible for regulating the DC-link voltage. In addition, these converters provided decoupled and bidirectional power flow control which enabled the DFIG to operate at sub synchronous and super synchronous speeds. A three-level VSC was chosen for the GSC control, where a resource conservative modulation algorithm that eliminates DC-link neutral voltage unbalance was implemented. The DFIG system design was simulated, and the results were verified through experimental tests performed on a 1.5kW wound rotor induction machine (WRIM). A detailed description of the laboratory setup of the DFIG is presented, and various practical limitations are discussed. It was found that the performance of the developed DFIG test rig correlated well with results of the simulations. Stable operation was achieved for various system test conditions, which indicated the system’s robustness to serve as a practical platform for future DFIG related research

Doubly fed induction generator with integrated energy storage system for smoothening of output power

Wind energy is one of the fastest growing renewable energies in the world today. However, integration of wind power into the power system network is still confronting many challenges. One of the main challenges is the suppression of wind power fluctuations. This thesis focuses on integration of wind power with energy storage to overcome the integration challenges. The first part of this thesis investigates the suitability of energy storage systems for transmission, distribution and wind farm applications. A review on the available energy storage systems is performed considering several criteria. Efforts are made to investigate solutions that meet all the power system requirements. In the second part of the thesis, a wind turbine generator with integrated energy storage system is modeled and studied for smoothening of the output power fluctuations due to changes in wind velocity. An ultra-capacitor is used as an energy storage system which is integrated into the doubly-fed induction generator through a bidirectional buck-boost dc-dc converter. Different modes of operation for the integrated system are studied and the simulation results verify the effectiveness of the designed model using the software package MATLAB/Simulink. The last part of the thesis focuses on application of the doubly-fed induction machine. The grid-side converter of the machine is used to supply harmonics for nearby non-linear loads. A multiple reference frame synchronous estimator and controller are used to track and eliminate the dynamically changing 6k ±1 harmonics on the power system network. This complete system is developed and tested using the software package PSCAD/EMTDC. The simulation results and the harmonic analysis verify the correct operation of the system --Abstract, page iii