Reliability assessment of different HVDC transmission system configurations considering transmission lines capacity restrictions and the effect of load level

Abstract The ongoing increasing demand for electrical energy and the reliable access to remote renewable energy generation points such as off-shore wind power stations or solar power generation, have revived the interest in HVDC multi-terminal systems. With the expansion of HVDC systems, their reliability assessment has become continuously important. One of the most important aspects of the reliability assessment of electrical systems is to have an accurate understanding of the engineering implications of the system and its associated components. The next step is to appropriately model the system components to represent their characteristics and functions in the overall system. In order to deliver a specified amount of electrical power, different methods can be considered. There are two general methods: 1) using several electrical power sources with low capacity, or 2) using fewer electrical power sources with high capacity. The decision to choose a certain method for transmitting electrical power depends on various parameters, and one of the most important parameters is reliability studies. This paper presents reliability modeling and analysis of HVDC transmission systems incorporating hybrid HVDC breakers to interrupt HVDC line faults. In this paper, comprehensive detailed reliability models of point-to-point, three-terminal, and four-terminal configurations are developed. Using this equivalent reliability model, various reliability indices are calculated at the load point of the system. Also, the effects of line constraints and incorporating DC circuit breakers of the DC transmission lines on the load point reliability indices have been evaluated. In the end, the effect of the load level on the reliability indices of the load point of each configuration has been assessed.