A Non-Intrusive Approach for Enhancing Power-System Frequency Stability

This paper presents a novel protection strategy for assuring power-system frequency stability. After many years of use, the existing (static) under-frequency load-shedding concept has proven to be reliable and fast. However, it does not adapt well to volatile operating conditions, which might often lead to a system collapse. This developed into a major obstacle, since operational conditions of modern power systems are persistently subjected to fast and unpredictable changes. Therefore, there is a need to introduce a new capability in under-frequency load-shedding that would be able to fine-tune the mismatch in active power in any conditions. From the practical aspect, a systematic implementation of improvements should not threaten system stability. In terms of cost, a minimum intervention in the existing concept is desirable. This is why we developed an effective upgrade of the existing concept by introducing a specialized group of intelligent electronic devices supported by a principal component analysis technique. This group should be operated alongside the existing solution to monitor the actual frequency conditions and to take over power-balancing when fine-tuning is required. This supports the existing load-shedding and improves the process of frequency stabilization.

I. Introduction

The electric power system (EPS) is one of the largest man-made artificial systems on the planet. It enables a quality of life that was never before available to the humankind. Since electrical energy is an integral part of our daily lives, any long blackouts have major negative social and economic impacts [1]. Therefore, power engineers are constantly striving towards improving the EPS performance. To mitigate the consequences of EPS malfunctions and most severe incidents, System Integrity Protection Schemes (SIPS) are implemented. One of the protective measures associated with SIPS is ensuring the frequency stability of EPS using under-frequency load-shedding (UFLS) [2]. The main objective of UFLS is to restore the balance between the generated and the consumed active power after a major deficit takes place. This is achieved by temporarily limiting the supply of electric energy to consumers.