Sharif Digital Repository

Increase of sensitive customers to power quality has raised concerns in industries regarding requirements of quality power supply. Uninterruptible Power Supplies (UPSs) are known as efficient tools in providing reliable power supply to sensitive customer. However, in a UPS, getting a desired output requires appropriate structural implementation and successful output voltage control. On the other hand, due to the increase in sensitive loads in customers, the output power range of UPSs has increased. Consequently, design and producing high power UPSs is not economical. In addition, tendency to have high reliability power supplies disrespect of their physical locations has moved researcher... 

In this thesis first of all the different approaches of control and parallel of multi-modular inverter system were investigated. These methods have been categorized and examined separately, and they were compared with each other in terms of quality and quantity. Afterwards, Active current sharing technique due to its high reliability was selected as the fundamental control approach. Among different ways for active current sharing, Avarage load sharing was chosen for its acceptable stability compared with other method. Approaching this goal, for the first time optimal control strategy and LQR method was proposed to parallel 3-phase inverters.At first, the problem was edited to be compatible... 

Nowadays, non-linear loads comprise an important part of electrical grids. One of the most essential sources of nonlinear loads is switching power supplies, which mainly include power electronic rectifiers. When power outage occurs, Uninterruptible Power Supplies (UPS) must be able to supply these loads. The nonlinearity of the load has a significant effect on the Total Harmonic Distortion (THD) of the output voltage, which may not be easily reduced, especially in three-phase inverters. Furthermore, the presence of isolating transformers in these power supplies limits the control of harmonics and intensifies the nonlinear effects of the system.In this Master Thesis, a disturbance observer is... 

One of the challenges that always exists in the field of Testing the performance of converters, uninterruptible power supplies (UPSs) , etc. is to provide various types of loads to be applied to these equipments and test the quality of their performance in various load conditions. Leading or Lagging Power Factor loads, harmonic loads and non-linear loads are mainly required in this investigation. The use of inductors, resistors, capacitors and other devices for these tests is an old solution. Their disadvantages include high price, large volume and very high power loss, which was the initial idea of making programmable loads. A current source converter with the ability to Sink and source the... 

Recently, The Earth has become warm rapidly over the past few years. This global warming is not only caused by natural phenomena, and further increased by humans and the amount of greenhouse gases in the atmosphere. Around 40 to 50 percent of energy consumption is related to information technology and communications. However, the rapid growth of electricity consumption in data centers, in addition to increased costs, data center challenges faced serious environmental pollution and more greenhouse gases. Use of renewable energy and reducing electricity costs in data centers are the important subjects for researchers around the world. Many researchers provide solutions to reduce environmental... 

In recent years, and with the development of information technology in various aspects of life, the growth of energy consumption in this sector has accelerated. With the advent of cloud computing and the development of its users, data centers have become one of the largest consumers of energy in the world. Adverse effects of fossil fuel consumption on the one hand and the global energy crisis as a limiting factor for development, on the other hand, have doubled the importance of managing the issue and reducing energy consumption in this sector. The two main energy-related concerns in data center construction are clean energy and energy management. The use of new energy and natural facilities... 

In recent years, the demands come to data centers have increased significantly, so huge amount of energy consumption, cost of this usage and environmental effects of data centers have become serious issues. Accordingly using solar energy to provide some portion of a data center’s energy usage can reduce environmental effects efficiently. Also smarter use of this energy could decrease overall cost of energy in data center. The demands that come to a data center are categorized to critical and non-critical workloads. Running of Non-critical workload (batch job) can be moved to another time according to its deadline. This work suggests a solution that schedules batch jobs considering solar...