Frequency regulation in wind integrated power system

This Thesis has broader implications in terms of improvement in wind generation modeling which is a current requirement for prospective operational planning tools for future grid. This thesis mainly deals with various modelling issues encountered in wind integrated power system for frequency regulation. Thesis provides development of grid code compatible, frequency responsive type 4 wind turbine generator system and analysis of the wind energy systems frequency regulation capability and their integration impact on interconnected power system.<br /

Prophet Hazrat Muhammad’s S.A.W Personal Names; Approaches of Contemporary Orientalists

In the sixteen to twenty-first centuries a number of Seerah books were written in the aspect of anti-Islamic view. Orientalists started to research on the Prophet Muhammad S.A.W different aspects of life. They started their biased research to fulfill their missionary aims. In that situation, the orientalists of the mid-nineteenth to the twenty-first century had changed their vision towards Islam and Prophet Muhammad’s S.A.W Seerah as well. These orientalists are less biased and show a soft image of Islam and Prophet Muhammad’s S.A.W Seerah. They show their positive face towards the East. Prophet Muhammad S.A.W carries an abundance of attributive names Asmā’u ’n-Nabiyy which are given on His S.A.W noble characteristics and also Allah Almighty calls his beloved Prophet S.A.W with different epithets. The main focus of this research work is to explore the approaches of orientalists and somehow clear the doubts of orientalists and western scholars of the modern age in regard to Prophet Muhammad’s S.A.W pious names

Frequency-Power Control of VSWTG for Improved Frequency Regulation

With increasing wind energy penetration and impending grid codes, it is important to enable wind-based power plants to provide sensitive frequency response in grids that may experience irregular frequency fluctuations with noise induced. Transient low-frequency deviations are handled by inertial control, while active power frequency response controller is needed for high-frequency control. A frequency processor-based frequency-active power set point controller architecture for variable speed wind turbine generator (VSWTG) is presented in this paper. Grid frequency processor based on moving averaged frequency and dynamic dead-band is tested for two different grid codes. Generated active power set point is provided to a modified torque-pitch control loop in type 3 and type 4 variable speed wind turbine generator generic models. Delay model of hydro system in a single area load frequency control is applied to investigate frequency support from proposed frequency response controller-based VSWTG. Area frequency response along with VSWTG electrical power support is compared with other droop-based VSWTG model to establish the superiority of proposed frequency-active power controller-based VSWTG over other droop-based VSWTG models

Automatic generation control of multigeneration power system

Load frequency Control (LFC) is used for many years as part of Automatic Generation Control (AGC) in power system around the world. In a mixed power system, it is usual to find an area regulated by hydro generation interconnected to another area regulated by thermal generation or in combination of both. In the following study, performance of AGC for Thermal, Hydro and Thermal turbine based power system is examined, including how frequency bias setting influences AGC responseand inadvertent interchange. Control performance analysis of three area interconnected systems is simulated and studied through Matlab Simulink software. Integral square error and Integral time absolute error has been used as performance criterion. It is shown that integral timeabsolute error (ITAE) as performance index leads to faster optimization of controller gain

Familial pattern of large vestibular aqueduct syndrome in a Chinese family

Large Vestibular Aqueduct Syndrome (LVAS) is the most common radiographic malformation in children with early onset of hearing loss. Usually its occurrence is non-familial, however intriguingly a portion of patients with LVAS is found to have evidence of genetic predisposition. We described cases of LVAS in two siblings of a Chinese family. The elder sister first presented with reduced hearing since childhood and her brother has a similar complaint upon further questioning. Their hearing test showed bilateral sensorineural hearing loss (SNHL) and computed tomography (CT) of temporal bone showed enlarged vestibular aqueduct in both patients. We described an approach to diagnosis of LVAS and highlight the importance of hearing assessment in genetic link hearing loss

Employing James Gee’s Analytic Lens for Identity to Investigate Teacher Identity Development

The current article is an exploration of the construction and development of teacher identities at the tertiary level in Pakistan. Identity is the sense of who one is as a professional, and it is becoming evident that it is important for teachers at all levels to develop a clear sense of identity as it leads to better practices and high level of commitment to the profession. The researcher adopted a constructivist stance for the investigation of identity and used data triangulation by using life histories, semi-structured interviews (based on the James Gee’s Lens for Identity) and fieldnotes as the sources of data. Six participants from urban tertiary institutions in various cities of Pakistan were selected and interviewed. The gathered data was analyzed iteratively through coding and contrastive analysis and highlighted the similarities and disparities of the various perspectives of identity; it was discovered that the participants had a better awareness and acceptance of their nature identity, whereas the institutional and discursive identities were the ones that posed conflict for them. The researcher also found that affinity identity was the weakest link in the Gee lens for teachers of Pakistan

Changing gender relations in small businesses: experiences of women entrepreneurs of Pakistani origin in Greater Manchester

This PhD contributes to the growing body of literature on South Asian women’s entrepreneurship in general, and on women of Pakistani origin in particular. The literature on the latter is comparatively scarce, and research on South Asian women’s entrepreneurship tends to overlook heterogeneity among these women. The research provides useful insights into Pakistani-origin women’s progress into and experiences of small business. An important contribution of this study is to develop new knowledge of Pakistani women’s diverse entrepreneurial roles and strategies in various business environments, such as, home-based, family and independent enterprises. The research draws theoretical insights from Brah’s multi-level framework and the ‘mixed embeddedness’ approach to conceptualise participation of women of Pakistani origin in small business. The analyses illustrate that gender practices and power relations in the family had an impact on Pakistani-origin women’s acquisition of human capital, access to resources and control of their labour, which subsequently affected their ability to exercise power and control in the family and business. The categories of business ‘leaders’ and ‘labourers’ shows that women’s business roles and experiences were diverse and embedded in complex and interwoven contexts, i.e. social, cultural, spatial, material and familial. A few of the businesses managed to ‘break out’ of the ethnic, spatial and sectoral boundaries. However, many others were strongly embedded in the existing ethnic structures. By and large, women’s business roles and performance were determined by their ability to accrue human capital, access to resources, command and control of their labour and ability to exercise power and control. The gender regimes of Pakistani families, communities and the wider British society not only determined performance of women’s business, but also transformed gender relations in many ways. An empowerment matrix I devised depicts changes in gender relations and levels of empowerment through participation in small business. Observation on levels of empowerment was mixed, which is depicted through: positive change/full empowerment, moderate change/empowerment, no change/status quo maintained and negative change/lessening of power

Issues and mitigations of wind energy penetrated network: Australian network case study

Longest geographically connected Australian power system is undergoing an unprecedented transition, under the effect of increased integration of renewable energy systems. This change in generation mix has implications for the whole interconnected system designs, its operational strategies and the regulatory framework. Frequency control policies about real-time balancing of demand and supply is one of the prominent and priority operational challenge requiring urgent attention. This paper reviews the Australian electricity market structure in presence of wind energy and its governance. Various issues related to increased wind generation systems integration are discussed in detail. Currently applied mitigations along with prospective mitigation methods requiring new or improved policies are also discussed. It is concluded that developing prospective frequency regulation ancillary services market desires further encouraging policies from governing authority to keep pace with current grid transition and maintain its security

Le syndrome de cushing chez l’adolescent: à propos de 18 patients

Le syndrome de Cushing est une pathologie rare mais grave chez l'enfant et l'adolescent. Elle diffère de la pathologie adulte par le mode de présentation et la prise en charge. Il s'agit d'une étude rétrospective des dossiers de patients suivis pour syndrome de Cushing au service d'endocrinologie de Casablanca entre 2002 - 2015, incluant les patients âgés au moment du diagnostic de moins de 22 ans, et ayant un suivi d'au moins 1 an. Au total 18 dossiers ont été inclus. L'âge moyen est de 19,55 ans, avec une prédominance féminine. La durée d'évolution moyenne est de 4,05 ans. Le tableau clinique est fait souvent d'une cassure de poids, une obésité ou une séborrhée et acné. La démarche diagnostique est comparable à celle de l'adulte. Sur le plan étiologique on retrouve une prédominance de la maladie de Cushing (15 patients). Sur le plan thérapeutique, 14 patients ont bénéficié d'une chirurgie hypophysaire, avec complément par radiothérapie chez 3 patients devant l'échec de la chirurgie, Une ablation d'une tumeur surrénalienne chez une patiente et une surrénalectomie bilatérale chez trois patients. L'évolution a été marquée par une guérison chez 9 patients et le décès chez 4 (suite à un syndrome de Nelson, infection sévère, choc hémorragique, corticosurrénalome). Les résultats de cette étude soulignent la gravité de cette maladie, ce qui nécessite d'organiser le suivi, en élaborant des programmes spécifiques de suivi médical et de prise en charge psychologique.Pan African Medical Journal 2015; 2

Optimising grid-forming inverters to prevent under-frequency load shedding with minimal energy storage

The increasing penetration of distributed photovoltaics decreases the available loads in distribution feeders. This makes the traditional under-frequency load shedding systems ineffective. As an alternative, large-scale energy storage systems (ESS) could be used to provide contingency frequency response. This study investigates the optimum sizing of the ESS to prevent under-frequency load shedding. The optimal size is determined for both droop and virtual synchronous generator control-based inverters, to maintain frequency within operating standards. The control parameters are treated as variables in the optimisation process, allowing the identification of the optimal set of control parameters that minimise the ESS size while preventing under — frequency load shedding. The power system is implemented in DIgSILENT PowerFactory, and the Hill climbing algorithm is used for optimisation. Given that a black box optimisation methodology is used, it is compatible with non-linear governor models and encrypted inverter-based models. Finally, a detailed analysis of the variations in the minimum active power rating for different control parameters is provided. A minimum energy storage power rating of 85 MVA is achieved when using virtual synchronous generator control. For droop control, the minimum storage capacity is 89 MVA. This analysis provides a deeper understanding of how different control parameters influence the required size of the energy storage system