Document Type : Original Research Paper

Authors

• M. Setareh
• A. Moradi Birgani

Faculty of Electrical Engineering, Shahid Beheshti University, Tehran, Iran.

Abstract

Background and Objectives: This paper proposes a novel formula to calculate the sensitivities of electromechanical modes with respect to generators active power changes. The generic ZIP load model is considered and the effect of various types of loads on the best paradigm of generators redispatch (GR) is investigated. Furthermore, transmission lines resistance are modeled in the proposed formulae; and the best GR schemes to improve the power system damping with considering and neglecting transmission lines resistance are compared.
Methods: Four energy functions are defined and the quadratic eigenvalue problem is applied to construct the framework of the proposed formula. The dynamic equation of the classical model of synchronous generators along with algebraic equations of power network considering transmission lines resistance and ZIP model of power system loads are written in a systematic manner using the partial differential of the energy functions. Then, set of equations of the power system are linearized and sensitivity factors are calculated using power system model parameters and power flow variables, which can be either obtained via state estimation or measured directly by phasor measurement units.
Results: The 39-bus New England power system is used to calculate sensitivities. The value of Sensitivity factors in conditions of considering transmission lines resistance and neglecting ones are compared and then the best GR plan to improve critical damping is determined. If all the loads are assumed to be in constant power mode, then for two modes with and without considering transmission lines resistance, generators pairs (9,1) and (5,2) are the best redispatch plans to damp oscillations. However, If all the loads are assumed to be in constant current mode, the best generators pair without considering transmission lines resistance mode does not change, although, it changes to generators pair (5,1) for the mode of considering transmission lines resistance.
Conclusion: Using the classical model of synchronous generators does not give information about the damping-ratio of the inter-area mode and only estimates its frequency well. Besides, considering the load model and resistance of transmission lines change the best paradigm of GR to damp oscillations.

Keywords

• Generators Redispatch
• Oscillatory Modes
• Sensitivities
• Transmission Line Resistance
• ZIP Load Model

Main Subjects

• Power System Operation and Analysis

Open Access

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Publisher

Shahid Rajaee Teacher Training University