چكيده به لاتين
The increasing demand for renewable energy resources such as offshore wind farms has necessitated the development of multi-terminal high voltage direct current (MTDC) systems. According to literatures, voltage source converter (VSC) based high voltage direct current (HVDC) systems are the best solution for realization of meshed HVDC grids. One of the most important challenges for implementation of HVDC grids is their high vulnerability against DC-side short circuit fault and uncontrollability of VSCs in DC fault conditions. Performance, reliability and controllability of HVDC systems strongly depend on a reliable protection system relying on HVDC circuit breaker (CB) to isolate the faulty part accurately, quickly and with high reliability. There are three main groups of HVDC CBs including electromechanical HVDC CB, pure solid-state HVDC CB and Hybrid HVDC CB. In order to deal with technical challenges such as operation speed, power transmission losses and transient recovery voltage, hybrid HVCD CBs are considered as the best option for HVDC grids.
In order to address the above challenges, this thesis presents simulation, operation analysis and comparison of three types of hybrid HVDC CBs to select the most appropriate design according to technical operation and economical considerations. In the simulation of control system of each CB, the internal protection model including self-level protection and driver level protection is considered to provide the possibility of autonomous operation of the CBs. The presented control logic for each CB is able to operate in every system situatoins such as switching under nominal system voltage, reclosing, DC fault clearing under correct performance either failure of system protection, and occurrence of multiple faults. The presented control logic has been validated by simulation study using PSCAD/EMTDC.
Keywords: Multi-terminal HVDC systems (MTDC), voltage source converter (VSC), DC short circuit fault, HVDC circuit breaker, hybrid HVDC circuit breaker
