Generator reactive power reserve management to prevent voltage collapse in Bangladesh power system

Abstract

Voltage stability has become a major concern in power system (PS) planning and operation and deals with power system adequacy and security. Highly stressed PS’ are being operated more often longer and closer to voltage stability (VS) limits and increases probability of instability and voltage collapse. Adequate voltage stability margin needs to be obtained through the appropriate scheduling of the reactive power resources. There is direct relation of generator reactive power reserves (GRPR) with voltage stability and voltage violations. The amount of reactive reserves at generating stations is a measure of the degree of voltage stability. As preventive measure, optimum GRPR to be maintained and managed so as to meet reactive power demands during voltage emergencies by fast acting automatic voltage regulator (AVR) operation. In Bangladesh Power System Network (BPSN), generating plants are mostly running at their highest capacity and no active or reactive power reserve is being kept for supporting system contingencies. Recurring system failures and collapses have been observed in BPSN. As a fast growing network, it is very important to study the network characteristics from voltage stability perspective, assess GRPR and formulate an effective and efficient reactive power management scheme and methodology for the operating and upcoming power plants. This thesis work presents the study on Bangladesh Power System for its voltage stability feature. Voltage profile of different buses have been investigated from real life data. Based on the basic connectivity and interconnection a simplified network model has been proposed. A load flow program has been provided based on the simplified model to assess the steady state Q-V and P-V sensitivities of different buses with incremental active and reactive load change. A methodology of generator reactive power reserve management has been proposed in this thesis work to enhance system voltage stability. The proposed methodology has been tested with dynamic simulation model and also verified its performance in a real life power plant. This methodology seems very practical and effective in Bangladesh perspective. If this control philosophy would be implemented in different power plants located in different places (geographically) in the network, will help to maintain better voltage stability and prevent system collapse due to voltage instability. Bangladesh power system is now in as state of ‘change’ as continual expansion of generation, transmission and distribution capacity. In this thesis, some inherent challenges in power system operation in Bangladesh have been presented which need further refinement.