0 AND 02 ADSORPTION ON Ag/Cu[100]

In this work the adsorption mechanisms of atomic and molecular oxygen on Cu(100) surface are studied using ab initio simulation methods. Through the atomistic scale under-standing of the elementary oxidation processes we can further understand the large-scale oxidation. Copper is a material widely used in industry which makes it an interesting subject, and also understanding the oxidation of copper helps us understand the oxidation mechanism of other metals. First we have a look on some theory on surface alloys in general and behaviour of Ag on Cu(100) surface. After that the physical background there is behind the methods of density functional calculations are discussed, and some methods, namely potential energy surfaces and molecular dynamics, are introduced. Then there is a brief look on the numerical details used in the calculations, and after that, the results of the simulations are exhibited.

Ruokalista 1881-01-02

Helsingfors 1881, F. Liewendal

Konserttiohjelma 1914-02-23 - Ohjelma

Helsinki 1914

Konserttiohjelma 1916-03-02 - [Ohjelma]

Helsinki 1916

Ruokalista 1909-02-13 - [Kansi]

[S.l.] 1909

Konserttiohjelma 1908-02-06 - (1)

Helsingfors : Kämp 1907, Öflund & Pettersson

Konserttiohjelma 1900-07-02 - Ohjelma

Helsinki 1900

Ruokalista 1911-02-14 - Menu - Vins

[S.l.] 1911

Minimizing Circulating Current in Parallel-Connected Photovoltaic Inverters

Parallel-connected photovoltaic inverters are required in large solar plants where it is not economically or technically reasonable to use a single inverter. Currently, parallel inverters require individual isolating transformers to cut the path for the circulating current. In this doctoral dissertation, the problem is approached by attempting to minimize the generated circulating current. The circulating current is a function of the generated common-mode voltages of the parallel inverters and can be minimized by synchronizing the inverters. The synchronization has previously been achieved by a communication link. However, in photovoltaic systems the inverters may be located far apart from each other. Thus, a control free of communication is desired. It is shown in this doctoral dissertation that the circulating current can also be obtained by a common-mode voltage measurement. A control method based on a short-time switching frequency transition is developed and tested with an actual photovoltaic environment of two parallel inverters connected to two 5 kW solar arrays. Controls based on the measurement of the circulating current and the common-mode voltage are generated and tested. A communication-free method of controlling the circulating current between parallelconnected inverters is developed and verified.

Theses (1827-02-03)

Painovuosi nimekkeestä.

Theses (1820-12-02)

Painovuosi nimekkeestä.

Theses (1826-02-11)

Painovuosi nimekkeestä.