A Multi-Stage Under-Voltage Load Shedding Scheme using a DIgSILENT power factory software to stabilize the power system network

Abstract

The electrical power system environment is based on generation, transmission and distribution. The best practice of the power system is that the generation plant must always be far from the consumers (load demand). The practice created a space where the power needs to be transmitted and distributed to the consumers. During this process, it is critical and important to keep the supply to the consumers at all times. Since the power systems are exposed to all vast condition, it is exposed to a dangerous environment. On the other hand, the load demand is continuously increasing and this can lead to power system instability. The objective of electrical engineers is to protect the power system and maintain stability. One of the best indicators that are used to monitor power system activities is the voltage. When power generation is not able to meet the load demand the system becomes unstable and this has become a concern last two decades. The paper presents Under-Voltage Load Shedding (UVLS) scheme is implemented in a multi-area power system network. The voltage studies are provided to get information and knowledge on how to develop an ideal under-voltage load shedding scheme. The objectives of the paper are to assist with deciding on the security of the system under the various conditions that can lead to power system stability. The objectives are mitigated by developing and implementing a multistage UVLS scheme for power utilities. The new proposed scheme is based on soft Intelligent Electronic Devices (IEDs). The proposed technique makes use of the DIgSILENT power factory platform where the whole system is modeled for simulations. A comprehensive case study is presented to analyze problems that are formed by voltage instability. The paper gives answers to questions such as: How and why does instability occur? What are the parameters or what are the main reasons for voltage instability? What are the key factors contributing to voltage instability? What are the voltage weak areas? What measures are most effective in improving voltage stability? based on the fundamental dependencies between the voltage, power, and current in power networks with loads. It also elaborates on the effect of power system instability when exposed to some contingency. The power flow study is deployed to determine the optimal system operating conditions of the IEEE39 bus system. Methods such as the PV curve and QV curve are applied in the paper to find the critical operation point before the voltage instability occurs in the power system. Five case studies were implemented where the proposed algorithm uses the Intelligent Electronic Devices (IED) to implement the Under Voltage Load Shedding (UVLS) scheme wherein a case the voltage elements are used for voltage monitoring. The developments in this paper extended the capability of the DIgSILENT power factory software to be used for more advanced power stabilities studies