The study of the angular distribution of photon plus jet events in pp collisions at √S =7 TeV with the Compact Muon Solenoid (CMS) detector is presented. The photon is restricted to the central region of the detector (|η| < 1.4442) while the jet is allowed to be present in both central and forward regions of CMS |η| < 2.4). Dominant backgrounds due to jets fragmenting into neutral mesons are accounted for through the use of a template method that discriminates between signal and background. The angular distribution, |η*|, is defined as the absolute value of the difference in η between the leading photon and leading jet in an event divided by two. The angular distribution ranging from 0-1.4 was examined and compared with next-to-leading order QCD predictions and was found to be in good agreement.

Indiana University-Purdue University Indianapolis (IUPUI) / This thesis deals with three phase inverters and the different control strategies that can be associated with an inverter being used together. The first part of this thesis discusses the present research in the fields of PV panels, motor drive systems and three phase inverters along with their control. This control includes various strategies like MPPT, Volts-Hertz and modulation index compensation. Incorporating these techniques together is the goal of this thesis. A new topology for operating an open end motor drive system has also been discusses, where a boost converter and a flyback converter have been used in cascade to run a three phase motor. The main advantage of this is increasing the number of levels and improving the quality of the output voltage, not to mention a few other benefits of having the proposed circuit. A new algorithm has also been designed for starting and stopping the motor, which controls the current drawn from the power source during starting.

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The McTronX research group, at the Potchefstroom campus of the North–West University, has been researching Active Magnetic Bearings (AMBs). A fully suspended, flywheel energy storage system (FESS) has been developed. Due to excessive unbalance on the rotor, the motor drive could not be tested up to its rated speed. In the interim, until the rotor can be balanced and other rotor dynamic effects have been investigated, the group decided that the existing drive control should be improved and tested on a high–speed permanent magnet synchronous motor (PMSM), using normal roller element bearings. In order to test the motor control a second (identical) PMSM, mechanically coupled to the former, operates in generator mode which serves as the torque load. Two different control algorithms, namely V/f and vector control, are designed and implemented on a rapid control prototyping system, i.e. dSPACE®. The V/f control is an open–loop, position sensorless technique, whilst the vector controller makes use of a position sensor. From the design and implementation it became clear that the vector control is more robust, in the sense that it is less sensitive on parameter variations and disturbances. It can start up reliably even under full load conditions. The V/f control is an attractive alternative to the vector control, especially in AMB systems, where it may be difficult to mount the position sensor, has to operate in a hazardous environment not suited to the sensor or could degrade the reliability of the AMB system. The cost of the position sensor is not really a concern compared to the cost of an AMB system. The V/f control is more suited to fan and pump applications, which has a low dynamic requirement. The V/f control has high startup currents and is not recommended for applications requiring a high starting torque or fast acceleration during operation. The inverter, which drives the PMSM, also had to be developed. With regard to the motor control, the effects of inverter non–idealities had to be accounted, especially for the V/f control. The implemented control algorithms were tested up to 20 krpm. Discrepancies between the expected and actual results are discussed. Overall, the controllers performed as desired. Generally, the project goals have been reached satisfactorily. / Thesis (M.Ing. (Computer and Electronic Engineering))--North-West University, Potchefstroom Campus, 2011.

The McTronX research group, at the Potchefstroom campus of the North–West University, has been researching Active Magnetic Bearings (AMBs). A fully suspended, flywheel energy storage system (FESS) has been developed. Due to excessive unbalance on the rotor, the motor drive could not be tested up to its rated speed. In the interim, until the rotor can be balanced and other rotor dynamic effects have been investigated, the group decided that the existing drive control should be improved and tested on a high–speed permanent magnet synchronous motor (PMSM), using normal roller element bearings. In order to test the motor control a second (identical) PMSM, mechanically coupled to the former, operates in generator mode which serves as the torque load. Two different control algorithms, namely V/f and vector control, are designed and implemented on a rapid control prototyping system, i.e. dSPACE®. The V/f control is an open–loop, position sensorless technique, whilst the vector controller makes use of a position sensor. From the design and implementation it became clear that the vector control is more robust, in the sense that it is less sensitive on parameter variations and disturbances. It can start up reliably even under full load conditions. The V/f control is an attractive alternative to the vector control, especially in AMB systems, where it may be difficult to mount the position sensor, has to operate in a hazardous environment not suited to the sensor or could degrade the reliability of the AMB system. The cost of the position sensor is not really a concern compared to the cost of an AMB system. The V/f control is more suited to fan and pump applications, which has a low dynamic requirement. The V/f control has high startup currents and is not recommended for applications requiring a high starting torque or fast acceleration during operation. The inverter, which drives the PMSM, also had to be developed. With regard to the motor control, the effects of inverter non–idealities had to be accounted, especially for the V/f control. The implemented control algorithms were tested up to 20 krpm. Discrepancies between the expected and actual results are discussed. Overall, the controllers performed as desired. Generally, the project goals have been reached satisfactorily. / Thesis (M.Ing. (Computer and Electronic Engineering))--North-West University, Potchefstroom Campus, 2011.

At present, one of the main issues in electric power networks is the reduction in conventional generation and its replacement by low inertia renewable energy generation. The balance between generation and demand has a direct impact on the system frequency and system inertia limits the frequency rate of change until compensation action can be undertaken. Traditionally generation managed frequency. In future, loads may be required to do more than just be able to be switched off during severe under frequency events. This thesis focuses on the development and practical implementation of the control structure of a smart adaptive load for network power-frequency support applications. The control structure developed makes use of advanced demand side management of fan loads (powered by AC drives) used in heating, ventilation, and air conditioning systems; where a change in power at rated load has little effect on their speed due to the cubic relationship between speed and power. The AC drive implemented in this thesis is based on an induction motor and a two level voltage source converter. To achieve the smart adaptive load functionality, first a power-frequency multi-slope droop control structure (feedforward control) is developed; relating the frequency limits imposed by the network supplier and the fan power-speed profile (Chapter 2, Fig 2.19). Secondly, this control structure is combined with the control developed, in Chapter 3, for the AC drive powering the fan load. The full development of the control structure of the AC drive, its tuning process and its practical implementation is given; an equation is developed to find suitable tuning parameters for the speed control of the nonlinear load (fan load), i.e. Eq. (3.59).The analysis and simulation results provided in Chapter 4 conclude that a fast control of the active power drawn by the AC drive is possible by controlling the electromagnetic torque (hence current) of the induction motor without disturbing the fan load overly. To achieve this, changes between closed loop speed control and open loop torque control (power control) are performed when needed. Two main issues were addressed before the hardware implementation of the smart adaptive load: the estimation of the network frequency under distorted voltage conditions, and the recovery period of the network frequency. In this thesis two slew rate limiters were implemented to deal with such situations. Other possible solutions are also outlined. Finally, experimental results in Chapter 5 support results given in Chapter 4. A full power-frequency response is achieved by the smart adaptive load within 3s.

The use of variable frequency drives in centrifugal pump applications has raised the question of how to select a drive. Clogging obstacles in waste water applications create unknown transient loads for the pump system. A sudden load increase occurrence can clog the pump if the drive cannot supply enough current to reach the motor’s torque demand. In order to select a suitable drive, an empirical approach has been implemented, investigating three different drives. Results have shown that selecting a drive with the highest possible overload capabilities, even if for a short time is most suitable. Operation in vector speed control gives the most reliable operation if an automatic parameter tuning is performed by the drive. / Användningen av frekvensomriktare i centrifugalpumpar har väckt fr ågan om hur en omriktare skall väljas. Igensättande objekt i avloppsvatten kan ge upphov till transienta laster i pumpsystemen. En oförutsedd lastökning kan sätta igen pumpen om frekvensomriktaren inte kan förse motorn tillräckligt med ström för att möta momentbehovet. För att välja en lämplig omriktare har ett empiriskt tillvägag ångssätt valts i en undersökning av tre olika omriktare. Resultat har visat att det är lämpligast att välja en omriktare med högst överbelastningskapacitet, även om under en kort tid. Vektor hastighetskontroll är metoden som ger stabil körning om omriktaren f ått automatiskt ställa in motorparametrarna.