AC distribution grid reconfiguration using flexible DC link architecture for increasing power delivery capacity during (n-1) contingency

Abstract

A practical issue faced by today's ac grid is the rapidly growing power demand on its aging infrastructure. One possibility to maximize the capacity of the existing infrastructure is to refurbish the ac links to operate under dc conditions using modular multilevel converters. In this paper, the idea is applied to restructure an actual medium voltage distribution system. Further, a systematic reconfiguration strategy is proposed to maintain high power delivery capacity even during (n-1) contingency. Contingency analysis is carried out for faults in different system components of the distribution grid. Towards this goal, novel concepts such as reconfigurable switch, dc link converter bypass and flexible dc to ac operational transition are proposed.

Boundaries of Operation for Refurbished Parallel AC–DC Reconfigurable Links in Distribution Grids

“…SSS bus voltage in kV and S actual is the RSS demand in MVA. The total link conductor loss P loss,C0 is given by (13),…”

Reliability, Efficiency and Cost Trade-offs for Medium Voltage Distribution Network Expansion using Refurbished AC-DC Reconfigurable Links

“…Some empirical evidence for supporting an assumption of operating dc voltage rating equal to peak of the rated cable ac voltage is offered in [10]. In [11] however, it was shown that this enhancement factor is achievable only under normal operating conditions. During (n-1) contingencies, some reconfiguration techniques maybe necessary to maintain the enhanced capacity of the refurbished dc system.…”

“…During (n-1) contingencies, some reconfiguration techniques maybe necessary to maintain the enhanced capacity of the refurbished dc system. Different system architectures and the corresponding capacity with contingency analysis is presented in [11].…”

“…Even though the physical capacity of the link conductors increases under dc operation, it was shown in [11] that during (n-1) contingencies, this is not necessarily true. Adequate reconfiguration strategies were developed that could maintain the power transfer capacity enhancement at 1.5 p.u and even improve it to 2 p.u.…”

“…3-cored cables are vulnerable to 3-conductor to ground faults. Since the refurbished dc system uses two conductors per link, four conductors of two dc links could go out of service if 3-core fault occurs in the system [11]. Not only this, even a single conductor to ground fault could result in the removal of all three cores during maintenance activity.…”