Commissioned for this report is Ramboll, Bridge and Tunnel Unit in Stockholm. The idea throughout the work has been to primarily help bridge designers compiling advice and instructions on how fatigue verification for railway bridges in reinforced concrete shall be performed under the new rules, the Eurocodes. After the introduction of the Eurocodes in 2011 has major problems emerged among designers around Sweden. In some areas, it differs in the calculation rules compared with rules from the Swedish Transport Administration and the National Board of Housing, Building and Planning calculation. Fatigue verification is one area where the new calculation rules are different from the past. A large part of the report has been to interpret and find the relevant information in the Eurocodes concerning fatigue. When questions or doubts have surfaced, this has been discussed with Elisabeth Helsing at the Swedish Transport Administration and bridge designers at Ramboll. The result is a report where the structure is organized in the way that the bridge designers can move from cover to cover and realize that fatigue verification in reality follows the same order as the report's sections. The issues have been resolved and reported regularly through the report with complementary findings as a result. Some of the greatest advances in the report are the load combinations to be used for the method for fatigue verification, how the dynamic factor and the magnification factor should be used and how the trainloads to be designed for each method for fatigue verification.

On-load tap changers and static synchronous compensators (STATCOM) are the main components for voltage regulation and power quality optimization in the power system. STATCOMs are used in both industrial applications and utility to stabilize the grid and reduce downtime. STATCOM is based on power electronics that is put together as a voltage source converter. However, as STATCOMs are connected in shunt, they provide voltage regulation indirect, by the injection of reactive power. Which might be insufficient for emerging grid codes and power systems with less inertia. This thesis’s purpose is to investigate a series voltage source converter (SVSC), which is connected in series with the grid. Series connected devices may provide better voltage regulating capabilities than shunt devices with the same amount of reactive power compensation, as it can regulate the voltage directly. The SVSC can also be used for power system compensation and power flow control. The SVSC consists of a Chain-Link Modular Multilevel Converter that is connected directly in series with the power system without a coupling transformer. The SVSC injects a voltage in quadrature with the current through the SVSC, this gives the SVSC the ability to emulate a reactance, along with increasing the voltage. The maximum injected voltage from the SVSC is 30% of the system voltage. As the voltage is injected in quadrature with the current, the SVSC can change to voltage more if the power factor is low. The SVSC is able to keep the voltage on the load side constant in several different load and grid scenarios. Furthermore, the SVSC was able to emulate both a capacitance and an inductance, and control the active power flow. However, the SVSC was not able to regulate the voltage as desired when the power factor is close to 1. / Lindningsomkopplare och static synchronous compensators (STATCOM) är de huvudsakliga komponenterna för spänningsreglering och elkvalité optimering i elnätet. STATCOMs används i både industrin och av elnätsägare för att stabilisera elnätet och minska driftstopp. STATCOM är baserat på kraftelektronik som är byggt till en voltage source converter. I alla fall, eftersom STATCOMs är anslutna i shunt med elnätet, kan de endast spänningsreglera indirekt, genom att tillföra reaktiv effekt. Vilket kan vara otillräckligt med nya elnätsregler och elnät med lägre tröghet. Den här avhandlingens syfte är att undersöka en series voltage source converter (SVSC), som är ansluten i serie med elnätet. Enheter som är anslutna i serie med elnätet kan leverera bättre spänningsreglering än enheter som är anslutna i shunt med samma mängd reaktiv effekt kompensering. SVSC:n kan också användas för lednings kompensering och effektflödes kontroll. SVSC:n består av en Chain-Link Modular Multilevel Converter som är ansluten i serie med elnätet utan en kopplingstransformator. SVSC genererar en spännings som är i kvadratur med strömmen genom SVSC:n, det gör att SVSC kan emulera en reaktans, men även öka spänningen. Den maximala spänningen från SVSC:n är 30% av systemspänningen. Eftersom spänningen är i kvadratur med strömmen, så kan SVSC ändra spänningen mer om effektfaktorn är låg. SVSC:n kan hålla spänningen konstant på last sidan under flera olika last- och elnäts scenarier. Dessutom kunde SVSC:n emulera både en induktans och kapacitans, och kontrollera det aktive effektflödet. Men, SVSC:n kunde inte reglera spänningen som önskat när effektfaktorn var nära 1.