Personal Statement
Energy resources have pushed the human society to develop rapidly, but excessive and inappropriate exploitation of energy resources have on the other hand brought about pollution and energy crisis. This phenomenon upsets me. I have maintained a keen interest in new energy and energy conservation, and have been motivated to probe into them.
The development of a solar inverter system is my first attempt to research into new energy and energy conservation, which happened to be the most important project that I have initiated during my undergraduate studies. In this research, I not only applied theory to practice but also figured out my research direction and interest. Considering that there were plenty of postgraduates doing the same research, I innovatively resorted to the Z-source inverter topology recently proposed by Professor Peng with Michigan State University, abandoning the widely used three-phase voltage inverter topology. However, this decision indeed posed quite a challenge for me, because little efforts had been made to study the Z-source inverter topology; I had little experience to draw on. After a thorough consideration, I proposed to design and test the modules separately. In addition, with reference to Professor Peng’s published papers, I preliminarily determined the parameters of capacitance and inductance in the circuit topology. During the project, I employed the simple boost and maximum boost control that were adopted by predecessors to analyze the third harmonic injection. To pursue less switching loss and harmonic output, I emulated an innovative control method with software, to wit, irregular sinusoidal PWM signal control, which had yielded a good result in practice. In addition, I managed to finish a thesis on this control method Non-sinusoidal Injection Control Strategy of Z-Source Inverter. The thesis is to be published in the 2012 International Conference on Manufacturing Engineering and Automation. Moreover, this project has significantly sharpened my communication and cooperative skills. Communication with the postgraduates was quite inspiring. In particular, in terms of the novel non-sinusoidal injection method, they helped me better understand the limitations of traditional control method, i.e. the more frequent the switching, the bigger the loss. In an effort to solve this problem, we superimposed the three voltages so as to offset bias voltage. After repeated trials and revisions, we managed to make each voltage be completely off switch in at least one third of the cycle and only one bridge arm need to be open during straight-through.
The success of the project could be attributed to the theoretical knowledge and research capacities that I have acquired during the undergraduate studies. In those four years, apart from working hard on basic courses such as mathematics and physics, I spent plenty of time learning the specialized courses ahead of the school schedule, acquainting myself with the professional knowledge as early as possible. In addition, I took an active part in practice. For example, in my sophomore year, I built a smart racing team and participated in a competition on behalf of the college. This was a project about car tracking and contestants were required to build a system on our own, including machinery, vehicles, electronics, algorithms and modeling. Soon we discovered that it was almost impossible for smart cars to make the turns smoothly and eliminate jitters while maintaining a high speed. To resolve this problem, I, at first, attempted to determine the value of the steering angle output and differential outputs of two wheels by using the PID algorithm. However, this algorithm failed to differentiate between greater and lesser curvature. Later, I employed the fitted
equation of higher degree to calculate more reliable output curve, which, however, burdened the processor with a huge amount of calculation. Ultimately, I conducted numerous tests for each input value interval and drew a table with the interpolation method. By referring to the table, the output value could be determined. In the meantime, I introduced the PID algorithm into each interval to avoid the jitter caused by the numerical jumps and the dead zone of output value being close to 0. From this project experience, I learned to organize and lead a team to fight for a common goal and to make full use of the search tools to collect information. These are skills beneficial to my research. It is also worthy of mentioning that our unremitting attempts to model and modify a nonlinear system have deepened my understanding of the classical control theory and equipped me with some modern control theories. Hence my graduation thesis was about control, named Vision-based Closed-loop Self-tuning PID-fuzzy Control Study.
Having accumulated some research experience, I began to work with postgraduates at the college on their programs. For example, I once spent some time doing research with the underwater acoustic communications research group, in which I was in charge of microcontroller programming when the group was trying to build the underwater acoustic communication model. In this process, I gained an in-depth understanding of the principle of this underwater sensor model and read piles of related academic papers. And based on this experience, I composed my first English paper The Study on Robot Control Using Underwater Sensor Network, which was published in the 2nd International Conference on Mechatronics and Intelligent Materials 2012. This is, without doubt, a milestone in my academic research. Additionally, I have also been in the aircraft design team for some time, involved in modeling the nonlinear system and designing the closed-loop circuit of PWM motor-drive control. Thanks to such invaluable experiences, I have learned a great many research methods and enhanced my research capacities.
As my learning and research experiences increase, I feel an even stronger desire to explore deeper into new energy and energy conservation. I dream to improve our lives and the environment by devoting myself to relevant research. And now my undergraduate study is coming to an end and my next step is to go further in the field of new energy. Therefore, I am determined to further my studies abroad and conduct research in this meaningful field that I intensely cherish under the guidance of excellent teachers in a better environment. The University of XXX is leading the research of new energy and energy conservation technologies. I firmly believe that studying in your university will bring me closer to my dream. In addition, your university enjoys a worldwide reputation, remarkable teaching staff, sophisticated scientific equipment and courses fit for me. Therefore, I wish to be admitted to the PHD program at your university. Your favorable consideration of my application will be highly appreciated.
(完整word版)美国研究生申请个人陈述PersonalStatement(适合喜欢做项目的同学)
