DG dynamic voltage support requirements for the reliable protection of reconfigurable networks

Abstract

The increase in the levels of penetration of distributed generation (DG) and the introduction of smart grid functionalities like network reconfiguration to the distribution network have made its fault current levels unpredictable and complicated the design of its protection. This paper studies the use of distribution grid code requirements, which regulate the fault response of DGs, to control the fault current levels in the network. The paper proposes an algorithm to follow when choosing the grid code requirements for DG dynamic voltage support that would allow for the continued use of traditional protection setups with sufficient speed and reliability; this would help avoid the need for more complicated schemes that heavily rely on an external communication layer that might negatively impact the reliability of the system. A motivating example is used to show that depending on the network configuration different voltage support requirements might be needed. By studying all possible configurations, a common range of requirements can be identified. The paper also considers changing the requirements progressively, such that requirements set for DGs currently connected can be different than those added in the future. This is demonstrated with a second case study where DGs are added in three phases. The results show that DGs added in later phases would need to be subject to stricter requirements than those connected in the initial phase.