Twin CWG systems Final report

Construction, operation, and maintenance of twin control moment gyroscope system for space vehicle motion simulato

Development of a digital twin for real-time simulation of a combustion engine-based power plant with battery storage and grid coupling

Coordinated control of combustion engine-based power plants with battery storage is the next big thing for optimising renewable energy. Digital twins can enable such sophisticated control but currently are too simplistic for the required insight. This study explores the feasibility of a fully physics-based combustion engine model in real-time co-simulation with an electrical power plant model, including battery storage. A detailed, crank-angle resolved, one-dimensional model of a large-bore stationary engine is reduced to a fast-running model (FRM). This engine digital twin is coupled with a complete power plant control model, developed in Simulink. Real-time functions are tested on a dedicated rapid-prototyping system using a target computer. Measurement data from the corresponding power plant infrastructure provide validation for the digital twin. The model-in-the-loop simulations show real-time results from both the standalone combustion and electric submodels mostly within 5% of measured values. The model coupling for fully predictive simulation was tested on a desktop computer, showing expected functionality and validity within 4% and 8% of the respective measured generator and converter outputs. However, execution time of the FRM needs reducing when moving to final hardware-in-the-loop implementation of a complete power plant model.© 2022 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).fi=vertaisarvioitu|en=peerReviewed

CONTROL STRATEGY OF MULTIROTOR PLATFORM UNDER NOMINAL AND FAULT CONDITIONS USING A DUAL-LOOP CONTROL SCHEME USED FOR EARTH-BASED SPACECRAFT CONTROL TESTING

Over the last decade, autonomous Unmanned Aerial Vehicles (UAVs) have seen increased usage in industrial, defense, research, and academic applications. Specific attention is given to multirotor platforms due to their high maneuverability, utility, and accessibility. As such, multirotors are often utilized in a variety of operating conditions such as populated areas, hazardous environments, inclement weather, etc. In this study, the effectiveness of multirotor platforms, specifically quadrotors, to behave as Earth-based satellite test platforms is discussed. Additionally, due to concerns over system operations under such circumstances, it becomes critical that multirotors are capable of operation despite experiencing undesired conditions and collisions which make the platform susceptible to on-board hardware faults. Without countermeasures to account for such faults, specifically actuator faults, a multirotors will experience catastrophic failure. In this thesis, a control strategy for a quadrotor under nominal and fault conditions is proposed. The process of defining the quadrotor dynamic model is discussed in detail. A dual-loop SMC/PID control scheme is proposed to control the attitude and position states of the nominal system. Actuator faults on-board the quadrotor are interpreted as motor performance losses, specifically loss in rotor speeds. To control a faulty system, an additive control scheme is implemented in conjunction with the nominal scheme. The quadrotor platform is developed via analysis of the various subcomponents. In addition, various physical parameters of the quadrotor are determined experimentally. Simulated and experimental testing showed promising results, and provide encouragement for further refinement in the future

Gear tooth stress measurements on the UH-60A helicopter transmission

The U.S. Army UH-60A (Black Hawk) 2200-kW (3000-hp) class twin-engine helicopter transmission was tested at the NASA Lewis Research Center. Results from these experimental (strain-gage) stress tests will enhance the data base for gear stress levels in transmissions of a similar power level. Strain-gage measurements were performed on the transmission's spiral-bevel combining pinions, the planetary Sun gear, and ring gear. Tests were performed at rated speed and at torque levels 25 to 100 percent that of rated. One measurement series was also taken at a 90 percent speed level. The largest stress found was 760 MPa (110 ksi) on the combining pinion fillet. This is 230 percent greater than the AGMA index stress. Corresponding mean and alternating stresses were 300 and 430 MPa (48 and 62 ksi). These values are within the range of successful test experience reported for other transmissions. On the fillet of the ring gear, the largest stress found was 410 MPa (59 ksi). The ring-gear peak stress was found to be 11 percent less than an analytical (computer simulation) value and it is 24 percent greater than the AGMA index stress. A peak compressive stress of 650 MPa (94 ksi) was found at the center of the Sun gear tooth root

Development of a converter for grid-tied and isolated operation of an interior permanent magnet synchronous generator, coupled to a twin-shaft gas turbine

South Africa’s overreliance on coal fired power generation has led to the government’s commitment to diversifying the country’s energy mix. Gas turbine generators are poised to play a larger role in South Africa’s energy mix, due to the country’s abundance in natural gas reserves. Therefore, there is a need to developed gas turbine emulation systems to investigate how this transition is to be implemented and to discover new efficient ways to generate power through gas turbines. This thesis presents the development of a twin-shaft gas turbine emulator. A DC-machine that accepts both torque and speed references is used to emulate the behaviour of the gas turbine according to a modified Rowen gas turbine model. The emulator is coupled to a 1.5kW interior permanent magnet synchronous generator (IPM). The power density of a DC-machine is significantly lower than that of a gas turbine of the same rating. Thus, the DC-machine is rated at double the rating of the IPM to overcome the high inertia it has when compared to a gas turbine of the same rating. This means that the DC-machine can produce large toques to successfully emulated the dynamic behaviour of the gas turbine. A maximum error 2.5% in the emulation of the gas turbine’s speed is reported. A two-level active converter is used to compare control strategies for an IPM. Ninety-degree torque angle (NTA) control, maximum torque per ampere (MTPA) control and unity power factor (UPF) control are compared for performance. The UPF and MTPA control result in the lowest and second lowest DC-link utilisation respectively when compared to NTA control. This is due to a negative d-axis current component as opposed to a zero d-axis current component in the case of NTA control. It is also concluded that to achieve a high power factor and torque development, a negative d-axis current component is required. UPF and MTPA control perform well in both categories, with UPF control and MTPA control resulting in the highest power factor and developed torque respectively. A fourth control strategy that maximises the efficiency of the IPM is developed experimentally. The maximum efficiency (ME) control strategy minimises mechanical, core, windage and conduction losses. It also results in near unity power factor and near maximum developed torque. A nonconventional control structure that involves control of the DC-link from the generatorside converter is presented. This frees the outer-loop control of load-side converter to regulate voltage across the load when the system is supplying power to an isolated load. This control structure also allows the grid-side converter to employ reactive power compensation, without having to regulate the DC-link voltage at the same time. In doing so, large grid currents are avoided. A recursive least squares (RLS) algorithm is used to separate negative and positive sequence current components during grid voltage unbalance. A method to minimise the presence of negative sequence components in the load current is presented and implemented successfully in an experiment

Fault Ride-Through Capacity Enhancement of Fixed Speed Wind Generator by A Modified Bridge-type Fault Current Limiter

Fault Ride-Through (FRT) is a common requirement to abide by grid code all over the world. In this work, to enhance the fault ride-through capability of a fixed speed wind generator system, a modified configuration of Bridge-Type Fault Current Limiter (BFCL) is proposed. To check the effectiveness of the proposed BFCL, its performance is compared with that of the Series Dynamic Braking Resistor (SDBR). A harmonic performance improvement by the proposed method is also analyzed. Three-line-to-ground (3LG), line-to-line (LL) and single-line-to-ground (1LG) faults were applied to one of the double circuit transmission lines connected to the wind generator system. Simulations were carried out using Matlab/Simulink software. Simulation results show that the proposed BFCL is very effective device to achieve the FRT and suppress fault current that eliminates the need for circuit breaker replacement. Also, the BFCL improves the harmonic performance and helps follow harmonic grid code. Moreover, it was found that the BFCL works better than the SDBR, and has some distinct advantages over the SDBR

Advances in the Field of Electrical Machines and Drives

Electrical machines and drives dominate our everyday lives. This is due to their numerous applications in industry, power production, home appliances, and transportation systems such as electric and hybrid electric vehicles, ships, and aircrafts. Their development follows rapid advances in science, engineering, and technology. Researchers around the world are extensively investigating electrical machines and drives because of their reliability, efficiency, performance, and fault-tolerant structure. In particular, there is a focus on the importance of utilizing these new trends in technology for energy saving and reducing greenhouse gas emissions. This Special Issue will provide the platform for researchers to present their recent work on advances in the field of electrical machines and drives, including special machines and their applications; new materials, including the insulation of electrical machines; new trends in diagnostics and condition monitoring; power electronics, control schemes, and algorithms for electrical drives; new topologies; and innovative applications

Flight evaluations of sliding mode fault tolerant controllers

This is the author accepted manuscript. The final version is available from the publisher via the DOI in this recordThis paper considers the development of fault tolerant controllers (FTC) and their application to aerospace system. In particular, given the extensive and growing literature in this area, this paper focusses on methods where the schemes have been implemented and flight tested. One thread of the fault tolerant control literature has involved sliding mode controllers. This paper considers a specific class of sliding mode FTC which incorporates control allocation to exploit over-actuation (which is typically present in aerospace systems). The paper describes implementations of these ideas on a small quadrotor UAV and also piloted flight tests on a full-scale twin-engined aircraft