Wind Turbine Reliability Improvement by Fault Tolerant Control

This thesis investigates wind turbine reliability improvement, utilizing model-based fault tolerant control, so that the wind turbine continues to operate satisfactorily with the same performance index in the presence of faults as in fault-free situations. Numerical simulations are conducted on the wind turbine bench mark model associated with the considered faults and comparison is made between the performance of the proposed controllers and industrial controllers illustrating the superiority of the proposed ones

Sensor fault detection and isolation: a game theoretic approach

This paper studies sensor fault detection using a game theoretic approach. Sensor fault detection is considered as change point analysis in the coefficients of a regression model. A new method for detecting faults, referred to as two-way fault detection, is introduced which defines a game between two players, i.e. the fault detectors. In this new strategic environment, assuming that the independent states of the regression model are known, the test statistics are derived and their finite sample distributions under the null hypothesis of no change are derived. These test statistics are useful for testing the fault existence, as well as, the pure and mixed Nash equilibriums are derived for at-most-one-change and epidemic change models. A differential game is also proposed and solved using the Pontryagin maximum principle. This solution is useful for studying the fault detection problem in unknown state cases. Kalman filter and linear matrix inequality methods are used in finding the Nash equilibrium for the case of unknown states. Illustrative examples are presented to show the existence of the Nash equilibriums. Also, the proposed fault detection scheme is numerically evaluated via its application on a practical system and its performance is compared with the cumulative sum method

Hot corrosion behaviour of new candidates for thermal barrier coatings application in turbine simulated environments

Thermal barrier coatings (TBCs) are used gas turbine engines. The current material of choice (YSZ) degrades when it contacts with impurities arise from low quality fuels such vanadium and sulfur. YSZ cannot be used in temperature higher than 900˚C. Higher efficiency and performance of gas turbine engines will require a new generation of thermal barrier coatings (TBCs). In current work, hot corrosion behavior of new candidates including Gd2Zr2O7, ZrO2 stabilized with Ta2O5, zirconia stabilized with both Ta2O5 and Y2O3 and zirconia stabilized with CeO2 and TiO2 is investigated. For YSZ case, the reaction between NaVO3 and Y2O3 produces YVO4 and leads to the transformation of tetragonal ZrO2 to monoclinic ZrO2. Comparing to YSZ, under a temperature of 1050 °C, Gd2Zr2O7 is found to be more stable, both thermally and chemically, than YSZ, and exhibits a better hot corrosion resistance. To examine the effect of stabilizing zirconia with tantalum oxide, different compositions of ZrO2-Ta2O5 samples in the presence of molten mixture of Na2SO4 + V2O5 at 1100˚C were tested. Hot corrosion results show that orthorhombic zirconium-tantalum oxide is more stable, both thermally and chemically in Na2SO4+V2O5 media at 1100˚C, and shows a better hot corrosion resistance than the tetragonal phase. When zirconia stabilized with yttria and tantalum oxide (TaYSZ sample), minor amounts of NaTaO3, TaVO5 and Ta9VO25 are formed as the hot corrosion products with only traceable amounts of YVO4. Due to the synergic effect of doping of zirconia with both Y2O3 and Ta2O5, the TaYSZ sample has a much better hot corrosion resistance than YSZ. In zirconia stabilized with CeO2 coating, the formation of CeVO4 crystals possibly postponed the formation of YVO4 and transformation of tetragonal zirconia to monoclinic. On surface of zirconia stabilized with TiO2 coating, TiVO4 crystals are significantly smaller (about 5µm in length) than the large plate shaped YVO4 and CeVO4 found on the YSZ and CSZ samples. TiSZ coating was found to have a better hot corrosion resistance at a temperature of 1050˚C than both YSZ and CSZ coatings

Wind Turbine Pitch Actuator Regulation for Efficient and Reliable Energy Conversion: A Fault-Tolerant Constrained Control Solution

Motivated for improving the efficiency and reliability of wind turbine energy conversion, this paper presents an advanced control design that enhances the power regulation efficiency and reliability. The constrained behavior of the wind turbine is taken into account, by using the barrier Lyapunov function in the analysis of the Lyapunov direct method. This, consequently, guarantees that the generated power remains within the desired bounds to satisfy the grid power demand. Moreover, a Nussbaum-type function is utilized in the control scheme, to cope with the unpredictable wind speed. This eliminates the need for accurate wind speed measurement or estimation. Furthermore, via properly designed adaptive laws, a robust actuator fault-tolerant capability is integrated into the scheme, handling the model uncertainty. Numerical simulations are performed on a high-fidelity wind turbine benchmark model, under different fault scenarios, to verify the effectiveness of the developed design. Furthermore, a Monte-Carlo analysis is exploited for the evaluation of the reliability and robustness characteristics against the model-reality mismatch, measurement errors and disturbance effects

Fault-tolerant neuro adaptive constrained control of wind turbines for power regulation with uncertain wind speed variation

This paper presents a novel adaptive fault-tolerant neural-based control design for wind turbines with an unknown dynamic and unknown wind speed. By utilizing the barrier Lyapunov function in the analysis of the Lyapunov direct method, the constrained behavior of the system is provided in which the rotor speed, its variation, and generated power remain in the desired bounds. In addition, input saturation is also considered in terms of smooth pitch actuator bounding. Furthermore, by utilizing a Nussbaum-type function in designing the control algorithm, the unpredictable wind speed variation is captured without requiring accurate wind speed measurement, observation, or estimation. Moreover, with the proposed adaptive analytic algorithms, together with the use of radial basis function neural networks, a robust, adaptive, and fault-tolerant control scheme is developed without the need for precise information about the wind turbine model nor the pitch actuator faults. Additionally, the computational cost of the resultant control law is reduced by utilizing a dynamic surface control technique. The effectiveness of the developed design is verified using theoretical analysis tools and illustrated by numerical simulations on a high-fidelity wind turbine benchmark model with different fault scenarios. Comparison of the achieved results to the ones that can be obtained via an available industrial controller shows the advantages of the proposed scheme

Redescription of Paracobitis rhadinaea (Regan, 1906) from Sistan Basin, Iran (Teleostei: Nemacheiliidae)

Paracobitis rhadinaea, a member of the family Nemacheiliidae, originally described by Regan in 1906 from Sistan basin, is poorely known by the rare materials. The inadequately studied species is redescribed on the base of freshly collected materials. The species differs from all other Paracobitis species by combination of the following characters: stout and elongated body; large size, up to 288 mm; a fully squamated body; slit like posterior nare; and midlateral series of large, irregular set and shaped dark, brown blotches. P. rhadinaea is endemic to Sistan, Iran

Evaluation of Lipid Profile and PCSK9 Serum Levels in Parkinson’s Patients in Comparison with Healthy Subjects

Introduction Up to now, limited and contradictory results have been published on the role of prognostic values of lipid profile molecules including: HDL (High Density Lipoprotein), LDL (Low Density Lipoprotein), TG (Triglyceride), Total Cholesterol and PCSK9 (Proprotein Convertase SubtilisinKexin type 9) molecule in occurrence and development of Parkinson’s disease (PD). The aim of this study was to investigate the role of lipid profile and PCSK9 in patients with PD and to compar it with healthy individuals. Methods and Results In the present case-evidence study, 32 individuals diagnosed with PD were compared with 32 healthy individuals. After receiving the  participant's consent forms, 5 ml blood was taken from vein and the level of HDL(High -Density Lipoprotein), LDL (Low-Density Lipoprotein), TG (Triglyceride),Total Cholesterol and PCSK9 in the blood samples were measured. The Elisa method was used for measuring PCSK9 level in blood serum. Data were analyzed using SPSS17 software. The P values smaller than 0.05 were considered significant. The mean age of participants in the PD and control group was 56.9±8.8 and 53.7±10.1 years respectively (P>0.05). Twenty seven individuals (87.1%) and 13 individuals (41.9%) in the PD group and control group were men, respectively. The remaining participants were women (P=0.000). LDL level (84.2±24.9 ml/dl vs. 105.5±16.8, P=0.000), HDL (45.5±8.7 ml/dl vs. 51.1±9.5 ml/dl, P=0.000), total cholesterol (155.3±31.2 ml/dl vs. 192.8±32.5 ml/dl P=0.000) were lower and TG level was higher in the PD group (133.3±79.3 ml/dl vs. 131.2±58.6 ml/dl, P=0.9) compared with the control group. PCSK9 level was higher in the PDgroup, but no significant difference was found (141.6±70 vs. 129.7±51 ng/ml, P=0.5). ConclusionsOur findings showed that individuals with PD have lower level of HDL, LDL and total cholesterol compared with the control group, but PCSK9 levels were same in both groups

The Effect of Replacing Sorghum Grains with Corn Along with Phytase and NSP Enzymes on Yield and Blood Parameters of Broilers

In this research, the effects of replacing grain sorghum with corn along with phytase and NSP enzymes on the performance and blood parameters of broiler chickens were investigated. Different levels of grain sorghum (0, 5, and 10%) and two levels of phytase enzyme and NSP (0 and 0.1%) were used in feeding broilers. At the end of the period (42 days old), blood samples were taken and blood serum parameters were measured. During the test period, the amount of feed consumed, daily weight gain, food conversion ratio, and carcass characteristics were measured. The experimental treatments include 1- control diet (without sorghum and no enzyme), 2- control diet + without sorghum + 0.1 enzyme, 3- control diet + 5% sorghum + without enzyme, 4- control diet + 5% sorghum + 1 0. enzyme, 5- control diet + 10% sorghum + no enzyme and 6- control diet + 10% sorghum + 0.1 enzyme. The statistical design used in this experiment was a 2x3 factorial method in the form of a completely random design, with 6 treatments and 3 repetitions (15 chickens in each repetition), and a total of 270 Ross 308 strain broiler chickens were used. The results of the feed consumption showed that there was a statistically significant difference in the main effect of sorghum in the first and sixth weeks and in the main effect of enzyme only in the last week (p<0.05). The results of live weight gain showed that a statistically significant difference was observed only in the main effect of sorghum in the fifth and sixth weeks (p<0.05), (p<0.05) so the ratio without sorghum had the highest amount of live weight. The results of food conversion ratio showed that only in the main effect of sorghum, a statistically significant difference was observed in the fifth week (p<0.05), so the diet without sorghum showed the highest food conversion ratio. The results of the carcass traits showed that a statistically significant difference in the weight of the liver, spleen, pancreas, small intestine, large intestine and, cecum was observed only in the main effect of sorghum (p<0.05). The results of blood tests at the end of the experiment showed that there was a statistically significant difference in the amount of cholesterol, HDL, and LDL in the main effect of sorghum (p<0.05). The general results of the research showed that the addition of different levels of sorghum and enzymes in the diet did not have a favorable effect on the amount of feed consumption, live weight, and carcass traits, but the level of 10% sorghum improved the food conversion ratio in some weeks of the experiment