Parameter tting will facilitate model validation of the generic dynamic model for type-3 WTGs. In this thesis, a test system including a single 1.5 MW DFIG has been built and tested in the PSCAD/EMTDC environment for dynamic responses. The data generated during these tests have been used as measurements for the parameter tting which is carried out using the unscented Kalman lter. Two variations of the generic type-3 WTG model (the detailed model and the simpli ed model) have been compared and used for parameter estimation. The detailed model is able to capture the dynamics caused by the converter and thus has been used for parameter tting when inputs are from a fault scenario. On the other hand, the simpli ed model works well for parameter tting when a wind speed disturbance is of interest. Given measurements from PSCAD, the estimated parameters using both models are indeed improvements compared to the original belief of the parameters in terms of prediction error.

Parameter tting will facilitate model validation of the generic dynamic model for type-3 WTGs. In this thesis, a test system including a single 1.5 MW DFIG has been built and tested in the PSCAD/EMTDC environment for dynamic responses. The data generated during these tests have been used as measurements for the parameter tting which is carried out using the unscented Kalman lter. Two variations of the generic type-3 WTG model (the detailed model and the simpli ed model) have been compared and used for parameter estimation. The detailed model is able to capture the dynamics caused by the converter and thus has been used for parameter tting when inputs are from a fault scenario. On the other hand, the simpli ed model works well for parameter tting when a wind speed disturbance is of interest. Given measurements from PSCAD, the estimated parameters using both models are indeed improvements compared to the original belief of the parameters in terms of prediction error.

This thesis report describes the modeling procedure for available the wind turbine generator (WTG) technologies. The models are generic in nature and manufacturer independent. These models are implemented on commercially available dynamic simulation software platforms like PSCAD/EMTDC and MATLAB/SIMULINK. A brief introduction to the available WTG types is provided to understand the technological differences and their key features. The related theoretical concepts to the working of a WTG are explained, which acts as an aid for model development and implementation. Using the theoretical concepts as basis, a WTG model is divided into four parts : 1. Aerodynamic model 2. Mechanical drive train model 3. Electrical machine model 4. Controller model Once the different parts of a WTG are introduced, a groundwork for model implementation on the software platforms is laid. A step-by-step process of implementing a PSCAD or MATLAB model of a WTG is introduced in this thesis. Starting with the most fundamental WTG technology such as fixed-speed also known as direct-connect wind turbine. The model implementation is adanvced to other superior technology like the dynamic rotor resistance control (DRR) and the doubly-fed induction generator (DFIG). To better understand the working of a DFIG, a current-source regulated model (without electrical machine) emulating the DFIG is built on both PSCAD and MATLAB. A full blown converter model of the DFIG with back-to-back converter is then built in PSCAD/EMTDC. An approach to determine the reactive power capability (Q limits) of a DFIG is described. Rotor current limitation and stator current limitation of the DFIG are considered in determining the minimum and maximum reactive power delievered by the DFIG. Variation in the Q limits of a DFIG for change in wind speed is analysed with two different wind speed scenarios. 1. Wind speed from cut-in to rated i.e. 6 m/s - 14 m/s. 2. Wind speed above rated to cut-out i.e. 14 m/s - 20 m/s. Such an analysis, is useful in determining the operating mode of the DFIG. At low wind speeds (below rated), the DFIG can be operated as a STATCOM for exporting and importing reactive power (similar to synchronous machines). While above rated wind speeds, the DFIG can be set to produce maximum active power. Using the DFIG current-source model implemented in MATLAB/SIMULINK, laboratory experiments to plot the power profile of the DFIG is explained. Another experiment to perform independent P-Q control of the DFIG is also included in this report. / text

This thesis develops design methodologies for megawatt(MW)-scale yokeless and segmented armature (YASA) generators for wind turbine applications. The methodologies include the electromagnetic, the structural and the thermal designs of a YASA generator. The design process starts with developing an analytical method to generate preliminary machine designs for a megawatt-scale YASA generator. This analytical approach considers both electromagnetic and structural aspects of a generator, the parameters of which were obtained and visualised on a design reference map. This new concept of displaying machine parameters is useful for a designer to identify the relationship between them. An optimisation tool using pseudo-weight approach is integrated into the analytical tool to determine a optimum machine design. This is a flexible optimisation tool, allowing the user to give priorities to each objective function. The analytical calculation has reduced the design space for suitable machine candidates to be applied in further finite element analysis (FEM). In finite element analysis of an optimised YASA machine, the electromagnetic performance of a 1 MW YASA generator was produced and verified with analytical and experiment results. This is followed by structural optimisation with finite element method, where a spider wheel with a support ring geometry is applied to the rotor plate. This reduces the structural weight by more than 50% while the structure retain strong stiffness. Finally, the cooling system of the stator of the YASA generator is studied and the cooling channels design is proposed. Simulation results show that the stator of a 1 MW YASA generator can be effectively cooled with forced air.

The thesis utilizes the analogy in dynamic equations between a mechanical and an electrical system to convert the steam-turbine, micro-turbine, wind-turbine and hydro-turbine generator mechanical model to equivalent electrical circuit models respectively. And based on the round rotor type and permanent magnetic rotor type synchronous generators¡¦ dynamic equations, as well as their electromagnetic torque equations, the equivalent electrical interface circuits were derived respectively. By using the interface circuit, the circuit model of synchronous generator and the equivalent electrical circuit model of turbine-generator mechanism can thus be combined into the electromechanical integrated circuit model (Thevenin¡¦s analogy circuit model and Norton's analogy circuit model). The electromechanical integrated circuit model is helpful for analyzing the energy conversion, power transmission and interactions between the mechanical and electrical systems for a turbine generator unit. In order to learn about these electromechanical interactions by using the proposed electromechanical integrated circuit model, the thesis has made a study on the torsional vibrations for a small gas turbine generator unit and for a large steam turbine generator unit respectively. By way of the frequency scanning and eigenvalue calculation, it is found that the torsional mode frequencies can be changed due to the electromechanical integration. Moreover, the small unit was more affected by the electromechanical integration than the large unit. Finally, we studied the effect of operations of an Electric Arc Furnaces (EAF) on torsional vibrations of a low capacity turbine generator. The electric system studied belongs to a practical steel plant in an industrial park. Based on the electromechanical integrated equivalent circuit model, a flywheel coupling shaft was designed. It is found by simulations that the coupling shaft can be quite effective in alleviating vibrations caused by the system unbalance arising from the EAF operations.

Abstract<p><p>This thesis deals with the operation of and winding short-circuit fault detection in a Doubly-Fed Induction Generator (DFIG) based Wind Turbine Generator System (WTGS). Both the faulted and faultless condition of operation has been studied, where the focus is on the electrical part of the system. The modelled electrical system is first simulated and the developed control system is then validated on a test bench. The test-bench component dimensioning is also discussed.<p><p>The faultless condition deals with the start-up and power production mode of operation. Control design based on the Proportional Integral (PI) control technique has been compared for power and torque control strategies against the Linear Quadratic Gaussian (LQG) control technique, at different operating points through the variable-speed region of WTGS operation following the maximum power curve of the system. It was found that the torque control strategy offered less degradation in performance for both the control techniques at operating points different for the one for which the control system was tuned. The start-up procedure of the DFIG based WTGS has been clarified and simplified. The phase difference between the stator and the grid voltage, which occurs due to the arbitrary rotor position when the rotor current control is activated, is minimized by using a sample-and-hold technique which eliminates the requirement of designing an additional controller. This method has been validated both in simulation and experiments.<p><p>The faulted condition of operation deals with the turn-turn short-circuit fault in the phase winding of the generator. The model of the generator, implemented using the winding-function approach, allows the fault to be created online both in a stator and a rotor phase. It has been demonstrated that the magnitude of the current harmonics, used extensively in literature for the Machine Current Signature Analysis (MCSA) technique for winding short-circuit fault detection, is very different when the location of the fault is changed to another coil within the phase winding. This makes the decision on the threshold selection for alarm generation difficult. Furthermore, the control system attenuates the current harmonics by an order of magnitude. This attenuation property is also demonstrated through experiments. The attention is then shifted to the negative-sequence current component, resulting from the winding unbalance, as a possible fault residual. Its suitability is tested in the presence of noise for scenarios with different fault locations, fault severity in terms of the number of shorted-turns and grid voltage unbalance. It is found that due to the presence of a control system the magnitude of the negative-sequence current, resulting from the fault, remains almost the same for all fault locations and fault severity. Thus, it was deemed more suitable as a fault residual. In order to obtain a fast detection method, the Cumulative Sum (CUSUM) algorithm was used. The test function is compared against a threshold, determined on the basis of expected residual magnitude and the time selected for detection, to generate an alarm. The validation is carried out with noise characteristics different from the ones used during the design and it is shown that the voltage unbalance alone is not able to trigger a false alarm. In all the scenarios considered, the detection was achieved within 40 ms despite the presence of measurement filters. / Doctorat en Sciences de l'ingénieur / info:eu-repo/semantics/nonPublished