Nonlinear fractional‐order power system stabilizer for multi‐machine power systems based on sliding mode technique

Abstract

SUMMARYThis paper presents two novel nonlinear fractional-order sliding mode controllers for power angle response improvement of multi-machine power systems. First, a nonlinear block control is used to handle nonlinearities of the interconnected power system. In the second step, a decentralized fractional-order sliding mode controller with a nonlinear sliding manifold is designed. Practical stability is achieved under the assumption that the upper bound of the fractional derivative of perturbations and interactions are known. However, when an unknown transient perturbation occurs in the system, it makes the evaluation of perturbation and interconnection upper bound troublesome. In the next step, an adaptive-fuzzy approximator is applied to fix the mentioned problem. The fuzzy approximator uses adjacent generators relative speed as own inputs, which is known as semi-decentralized control strategy. For both cases, the stability of the closed-loop system is analyzed by the fractional-order stability theorems. Simulation results for a three-machine power system with two types of faults are illustrated to show the performance of the proposed robust controllers versus the conventional sliding mode. Additionally, the fractional parameter effects on the system transient response and the excitation voltage amplitude and chattering are demonstrated in the absence of the fuzzy approximator. Finally, the suggested controller is combined with a simple voltage regulator in order to keep the system synchronism and restrain the terminal voltage variations at the same time.

Decentralized multi-machine power system excitation control using continuous higher-order sliding mode technique

“…SMC has also been reported as one of the most effective control method in improving power system stability, due to its invariance properties and robustness [4,16,10,17,18]. Though improved oscillations damping and fast transient dynamic behavior are received, these classical firstorder SMCs [4,16,10,17,18] may lose robustness when considering the exciter's dynamics, and the unexpected chattering phenomenon of excitation control voltage is rather serious. The chattering effect may excite the electrical unmodeled dynamics, and is manifested as vibration in the mechanical parts and undesirable heat losses, which can lead to a low control accuracy and cause mechanical loss.…”

Design of a multi-mode intelligent model predictive control strategy for hydroelectric generating unit

“…As an economic and effective way to enhance power system stability, a multitude of efforts based on different control theories including PID control [2], fractional-order PID control [7,8], fuzzy control [9,10], nonlinear observer-based control [6], nonlinear decentralized robust control [5] and synergetic control [11,12] have been studied and applied in governing and excitation controls for improving dynamic performances and transient stability of the generating units, but most of these control methods have been designed specifically for a certain operating condition or have linearized or partially linearized the dynamic models of the turbine or the generator. With the development trend of power system control now concentrating on using nonlinear control theories to solve large systems described by higher dimensional nonlinear models with multiple state variables, NMPC theory which is regarded as an advanced control technique and is able to deal with complex control problems involved with multivariable process interactions, non-minimum phase behavior and systems represented by a nonlinear model [13,14] has been applied in turbine or generator control for power system in recent years [4,15].…”

Analysis on Nonlinear Dynamic Characteristic of Synchronous Generator Rotor System

“…For a three-machine power system, Majidabad et al [17] designed two novel nonlinear fractional-order sliding 2 Complexity mode controllers and applied them in a three-machine power system with two types of faults. Jiang et al [18] proposed a Weierstrass-based numerical method for computing damping torque of a three-machine power system during transient period to determine appropriate and accurate damping terms for power system dynamic simulation.…”