Frequency Load Shedding Scheme Research Articles

Centralized Adaptive Under Frequency Load Shedding Schemes for Smart Grid Using Synchronous Phase Measurement Unit

Under frequency load shedding (UFLS) is an effective way to prevent system blackout after a serious disturbance occurs in a power system. A novel centralized adaptive under frequency load shedding (AUFLS) scheme using the synchronous phase measurement unit (PMU) is proposed in this paper. Two main stages are consisted of in the developed technique. In the first stage, the active power deficit is estimated by using the simplest expression of the generator swing equation and static load model since the frequency, voltages and their rate of change can be obtained by means of measurements in real-time from various devices such as phase measurement units. In the second stage, the UFLS schemes are adapted to the estimated magnitude based on the presented model. The effectiveness of the proposed AUFLS scheme is investigated simulating different disturbance in IEEE 10-generator 39-bus New England test system.

Synchrophasor Associated Adaptive Control Strategy for Under Frequency Protection and Load Shedding in Smart Grid

A novel adaptive control strategy for under frequency protection and load shedding associated with synchronous phase measurement unit (PMU) is proposed in this paper. With the help of the PMU, the magnitude of active power deficit is estimated by using the simplest expression of the generator swing equation and static load model since the frequency, voltages and their rate of change can be obtained by means of measurements in real-time. Then, a robust control strategy with consideration of the uncertainties in system is presented. In the proposed robust control strategy, the under frequency load shedding (UFLS) schemes are used to prevent system frequency collapse. And minimal amounts of remote information are required. The effectiveness and robustness of the proposed control strategy investigated carrying out on 17-generator 69-bus test system under various disturbance scenarios

Research on the Frequency Dynamic Characteristics and UFLS Scheme in Shanghai Subzone Power Grid

Shanghai main power grid is operating in 500 kV ring network and with voltage-grading & district-dividing structure, and its subzone power grids have their own frequency characteristics. The paper has used district-dividing single equivalent model to check the parameters of components in BPA transient simulation program, and the original under frequency load shedding (UFLS) scheme was improved. Then the frequency dynamic characteristics of isolated subzone grid is analyzed, so does the adaptability and frequency safety of power grid under the new UFLS scheme in the condition of peak load in the summer of 2011.

A Synchrophasor Assisted Frequency and Voltage Stability Based Load Shedding Scheme for Self-Healing of Power System

This paper presents a new scheme for load curtailment in the power system required for its self-healing under critical contingencies, which may pose a threat to frequency as well as the voltage stability of the system. The load shedding requirement in the system has been calculated based on the computed disturbance power as well as the voltage stability condition of the system, with the aid of real-time data, assumed to be available from the synchrophasor based wide area monitoring and control system (WAMCS). This scheme assesses voltage stability based on a dynamic voltage stability criterion, formulated using a Voltage Stability Risk Index (VSRI). Suitable locations for the load curtailments have been chosen according to the VSRI, calculated at each load bus. Performance of the proposed scheme has been tested on New England 39-bus system and a practical 246-bus Indian system. The results are compared with a conventional under frequency load shedding scheme and an adaptive load shedding scheme.

Design of New Load Shedding Special Protection Schemes for a Double Area Power System

In this paper several Under Frequency Load Shedding (UFLS) schemes are designed as special protection schemes to preserve the integrity of islands, formed following the outage of tie lines connecting two areas in a double area power system. For the purpose of analysis, the Iranian interconnected grid is simulated in a suitable power system analysis software. The grid is connected to the Khorasan province network, the greatest province of the country, through a double circuit tie line. Following the outage of tie lines in a double area power system the area with great import of power may face large deficiency of energy and consequently blackout may occur in the island. The purpose of this research work is to propose a special protection scheme, being capable of preserving the balance of generation and consumption in order to prevent major outage. Special types of adaptive UFLS scheme are proposed in this work.

A microcomputer based integrated generation and transmission system simulator

An integrated generation and transmission simulator has been developed to serve as a tool to complement the teaching of power system operation, control, and protection. The simulator provides a hands-on exercise for the student to operate a generation and transmission system with a man-machine interface similar to that commonly used in a control center. Unit commitment, economic load dispatch, system dynamics, under frequency load-shedding schemes, load flow and modeling of overcurrent relays and overload tripping are integrated into the simulator. A built-in assessment scheme monitors the student's actions and generates a fair and consistent grade to all students. >