Power System Stability Enhancement Research Articles

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English

Electra IRP voltage control strategy for enhancing power system stability in future grid architectures

The research leading to these results has received funding from the European Union Seventh Framework Programme (FP7/2007– 2013) under grant agreement no. 609687.

Nonlinear Synergetic Governor Controllers for Steam Turbine Generators to Enhance Power System Stability

This paper proposes a decentralized nonlinear synergetic governor controller (NSGC) for turbine generators to enhance power system stability by using synergetic control theory and the feedback linearization technique. The precise feedback linearization model of a turbine-generator with a steam valve control is obtained, at first, by using a feedback linearization technique. Then based on this model, a manifold is defined as a linear combination of the deviation of the rotor angle, speed deviation, and speed derivative. The control law of the proposed NSGC is deduced and the stability condition of the whole closed-loop system is subsequently analyzed. According to the requirement of the primary frequency regulation, an additional proportional integral (PI) controller is designed to dynamically track the steady-state value of the rotor angle. Case studies are undertaken based on a single-machine infinite-bus system and the New England system, respectively. Simulation results show that the proposed NSGC can suppress the power oscillations and improve transient stability more effectively in comparison with the conventional proportional-integral-derivative (PID) governor controller. Moreover, the proposed NSGC is robust to the variations of the system operating conditions.

Nonlinear Observer-Based Robust Passive Control of Doubly-Fed Induction Generators for Power System Stability Enhancement via Energy Reshaping

The large-scale penetration of wind power might lead to degradation of the power system stability due to its inherent feature of randomness. Hence, proper control designs which can effectively handle various uncertainties become very crucial. This paper designs a novel robust passive control (RPC) scheme of a doubly-fed induction generator (DFIG) for power system stability enhancement. The combinatorial effect of generator nonlinearities and parameter uncertainties, unmodelled dynamics, wind speed randomness, is aggregated into a perturbation, which is rapidly estimated by a nonlinear extended state observer (ESO) in real-time. Then, the perturbation estimate is fully compensated by a robust passive controller to realize a globally consistent control performance, in which the energy of the closed-loop system is carefully reshaped through output feedback passification, such that a considerable system damping can be injected to improve the transient responses of DFIG in various operation conditions of power systems. Six case studies are carried out while simulation results verify that RPC can rapidly stabilize the disturbed DFIG system much faster with less overshoot, as well as supress power oscillations more effectively compared to that of linear proportional-integral-derivative (PID) control and nonlinear feedback linearization control (FLC).

Levenberg–Marquardt neural network to estimate UPFC-coordinated PSS parameters to enhance power system stability

Due to the presence of weak tie line interconnections, small signal oscillations are created in power system networks. Damping out these oscillations is one of the most crucial issues to be settled down for the stability of power system industry. The employment of flexible AC transmission systems (FACTS) may suppress these oscillations effectively in addition to the enhancement of power transfer capability. Unified power flow controller (UPFC) is one of those FACTS devices which are installed in the powers grids, which ensures proper functionality of high-voltage transmission lines. To select the proper parameters of power system stabilizer (PSS) when applied with UPFC is a challenge in this field which can be represented as a multi-objective optimization problem. This work aims to optimize the PSS parameters of power network incorporating UPFC using the artificial neural network (ANN) in real time to damp out the small signal oscillations with a view to enhancing the stability of the power system where the Levenberg–Marquardt (LM) algorithm is used as the training algorithm. System eigenvalues obtained from ANN-tuned PSS coordinated with UPFC and the fixed gain conventional PSS with UPFC are compared to investigate the efficiency of the proposed technique for different loading conditions. Additionally, the comparison has been made in time domain simulation results which prove the superiority of the proposed technique over conventional technique. Moreover, the satisfactory values of statistical performance measures validate the efficacy of the prediction capability of the proposed LM-NN approach.

Design and Implementation of Delay-Dependent Wide-Area Damping Control for Stability Enhancement of Power Systems

In this paper, the hardware and software design and implementation are proposed for the wide-area damping control (WADC) strategies. First, the hardware-in-the-loop (HIL) real-time (RT) simulation system based on the RT-Lab is established as the closed-loop test platform for the WADC applied in multi-machine interconnected power system. The hardware, which contains the microcontroller, the peripheral analog to digital converter, and the digital to analog converter, are developed based on the AVR 32-bit development board. Three WADC algorithms, i.e., the phase-compensation, the delay-dependent state-feedback, and the dynamic output-feedback method, are introduced. Then, the software design of the above algorithms is proposed and the bilinear transform method is employed to get the discrete-time model of the controllers. The flowchart of each algorithm is designed for the implementation in the environment of hardware. The designed WADC is embedded in a real-time power system. Finally, case studies are carried out based on the HIL real-time simulation system. The proposed control concept and WADC design methods are validated by considering the big/small disturbance and the signal time-varying delay. The effectiveness of the proposed HIL closed-loop test system is also confirmed.

An optimal/adaptive reclosing technique for transient stability enhancement under single pole tripping

This paper presents an integrated autoreclosure scheme (IAS) for transmission networks. The IAS operation is based on merging the functional advantages of the adaptive reclosing technique (ART) and the optimal reclosing technique (ORT). The ART identifies the nature of the fault, transient or a permanent fault, and determines the fault persistence time of a transient fault by analyzing the harmonic of the fault phase voltage using wavelet packet transform (WPT). The ORT is dependent on the load angle of the generators that minimizes the systems oscillation. The resulted information from the adaptive reclosing and the optimal reclosure timing units can effectively settled to achieve the optimum reclosing strategy that able to enhance power system stability. The proposed IAS is merited by an adaptive threshold level while needed information are captured from single end only. The IAS performance assessment compared to conventional reclosing schemes is carried out by using proposed voltage and speed indices. Examination of the proposed IAS is successfully achieved at different fault scenarios that involve various fault locations, inception angles, and representation of secondary arc characteristics. Added to that, the capability of the proposed scheme is confirmed considering the effects of shunt compensators, reactors and capacitors. Numerous simulation studies are emulated using MATLAB/SIMULINK on two test systems with different configurations. Simulation results indicate that the proposed reclosing method can enhance the transient stability.

Design considerations of superconducting fault current limiters for power system stability enhancement

This study identifies the type and size of the optimal shunt limiting impedance for superconducting fault current limiter (SFCL). Since the shunt impedance has been widely categorised to be either inductive or resistive element depending on the type of limiting impedance, the proposed design considerations will significantly affect the transient response and system stability. Therefore, the presented problem formulation optimises the design of SFCL by allowing the limiting shunt impedance to combine both resistive and inductive elements with an optimal ratio to tackle the security and stability challenges while functioning the SFCL. The optimisation framework is developed based on time-domain simulation and takes into account the transient stability indices to size the limiting components of SFCLs given that the main operational requirements such as fault current level and voltage limits are met. Non-dominated sorting genetic algorithm II is used to find the Pareto fronts for different types of SFCLs. The optimisation and time-domain simulation results demonstrate great enhancement in the performance of both SFCLs when the optimal ratio between the resistive and inductive elements is chosen for the shunt limiting impedance resulted in improving the transient response and system stability.

Enhancement of Power System Stability Using a Novel Power System Stabilizer with Large Critical Gain

Power system stabilizers (PSSs) are widely used for suppressing low frequency oscillations in practical power systems. However, according to the requirement of the “guide for setting test of power system stabilizer” of China, PSS gain is limited to no more than 1/3 of its critical gain. As a result, PSSs may not provide enough damping to the inter-area mode oscillations. Through analyzing the Heffron-Phillips (H-P) model of the generator with PSS, it is found that exciter mode will become unstable when PSS exceeds its critical gain. This exciter mode is formed by the natural characteristic of the exciter-PSS loop. To address this problem, a novel PSS with a parallel component added to the conventional PSS is proposed to improve its critical gain. Therefore, large gain can be chosen for the proposed PSS to meet the critical gain requirements of the guide and provide enough damping to the inter-area modes simultaneously. Simulation results on the Ximeng coal power station of China verify the effectiveness of the proposed PSS.

Stability Enhancement of an Industrial Power System by AVR Gain Readjustment

Excitation systems of synchronous generators contribute to effective voltage control and power system stability. Although the excitation system is tuned to enable the power system performs properly over a wide range of operating conditions, it may be necessary to retune it with the aim of improving the system stability during operating conditions not considered before. This paper shows how an unstable operating condition, of an oil refinery electric power system, after the occurrence of two simultaneous events may be avoided by simply adjusting the automatic voltage regulator gain in one of its synchronous generators.

RETRACTED ARTICLE: Dynamic stability enhancement of interconnected multi-source power systems using hierarchical ANFIS controller-TCSC based on multi-objective PSO

Suppression of the dynamic oscillations of tie-line power exchanges and frequency in the affected interconnected power systems due to loading-condition changes has been assigned as a prominent duty of automatic generation control (AGC). To alleviate the system oscillation resulting from such load changes, implementation of flexible AC transmission systems (FACTSs) can be considered as one of the practical and effective solutions. In this paper, a thyristor-controlled series compensator (TCSC), which is one series type of the FACTS family, is used to augment the overall dynamic performance of a multi-area multi-source interconnected power system. To this end, we have used a hierarchical adaptive neuro-fuzzy inference system controller-TCSC (HANFISC-TCSC) to abate the two important issues in multi-area interconnected power systems, i.e., low-frequency oscillations and tie-line power exchange deviations. For this purpose, a multi-objective optimization technique is inevitable. Multi-objective particle swarm optimization (MOPSO) has been chosen for this optimization problem, owing to its high performance in untangling non-linear objectives. The efficiency of the suggested HANFISC-TCSC has been precisely evaluated and compared with that of the conventional MOPSO-TCSC in two different multi-area interconnected power systems, i.e., two-area hydro-thermal-diesel and three-area hydro-thermal power systems. The simulation results obtained from both power systems have transparently certified the high performance of HANFISC-TCSC compared to the conventional MOPSO-TCSC.

Voltage Stability Enhancement in Power Systems with Automatic Facts Device Allocation

Abstract The voltage stability problem in modern power systems is an issue related to the system constraints and voltage collapse. Flexible AC Transmission System (FACTS) is an example of modern device able to control the reactive power flow in a more efficient way. This paper proposes an automatic FACTS device allocation process based on evolutionary algorithm. The model aims to enhance the voltage stability of power systems. The results showed that the proposed method enhanced the voltage stability in IEEE system benchmarks, and the method outperformed other probabilistic and heuristic optimization methods.

An Accurate Technique for Discrimination between Transient and Permanent Faults in Transmission Networks

This paper presents an assessment study for adaptive single-pole automatic reclosure (ASPAR) schemes to select correctly the best scheme at responsible indices. Suggested solutions for the drawbacks that were noticed with the previous methods are investigated. In addition, this paper presents a proposed technique for ASPAR on transmission lines using wavelet packet transform (WPT). The ASPAR aims to discriminate between the faults' natures and to detect the instant of arc extinguished. The proposed technique uses an adaptive threshold level, and therefore, no adjustment is needed for various transmission systems. The proposed technique is examined at different fault scenarios that involve different fault locations, inception angles, and representation to secondary arc characteristics with various arc models. In addition, the behavior of ASPAR is well studied under power swing situation. The effects of shunt reactor compensators on the proposed technique are checked. The proposed scheme is tested for different network configurations, single and double circuits, to realize the robustness and the capability of the proposed scheme. The ATP/EMTP package is developed to emulate different fault signals to validate the proposed scheme. The proposed adaptive threshold scheme discriminates correctly between permanent and transient faults, thereby enhancing power system stability for compensated and uncompensated networks.

Transient Stability Enhancement of Power System by Using Energy Storage System

Transient Stability Enhancement of Power System by Using Energy Storage System

A Multi-Model Approach to Design a Robust SVC Damping Controller Using Convex Optimization Technique to Enhance the Damping of Inter-Area Oscillations Considering Time Delay

This paper introduces a multi-model approach to design a robust supplementary damping controller. The designed fixed-order supplementary damping controller adjusts the voltage reference set point of SVC. There are two main objectives of the controller design, damping low frequencies oscillations and enhancing power system stability. This method relies on shaping the closed-loop sensitivity functions in the Nyquist plot under the constraints of these functions. These constraints can be linearized by choosing a desired open-loop transfer function. The robust controller is designed to minimize the error between the open-loop of the original plant model and the desired transfer functions. These outcomes can be achieved by using convex optimization methods. Convexity of the problem formulation ensures global optimality. One of the advantages of the proposed approach is that the approach accounts for multi-model uncertainty. In contrast to the methods available in the literature, the proposed approach deals with full-order model (i.e., model reduction is not required) with lower controller order. The issue of time delay of feedback signals has been addressed in this paper for different values of time delay by applying a multi-model optimization technique. The proposed approach is compared to other existing techniques to design a robust controller which is based on H2 under pole placement. Both techniques are applied to the 68-bus system to evaluate and validate the robust controller performance under different load scenarios and different wind generations.

Design of Modified Maiden Power System Stabilizer Using Cuckoo Search Algorithm

This article presents an improved maiden power system stabilizer (PSS) for enhancement of small signal stability of a power system. The free coefficients of proposed PSS are determined using optimization technique with the cuckoo search algorithms (CS-PSS). The performance of the CS-PSS is validated on single-machine infinite-bus power and extended to a multi-machine power system. These results are compared to the newly introduced maiden PSS structure and found superior in terms of settling time and performance indices.

Integration of Unified Power Flow Controller with Backup Energy Supply System for Enhancing Power System Stability

Integration of Unified Power Flow Controller with Backup Energy Supply System for Enhancing Power System Stability

Controller Design of SSSC for power System Stability Enhancement

In this paper, a novel method is developed for designing the output feedback controller for Static Synchronous Series Compensator (SSSC). In the proposed method, the problem of selecting the output feedback gains for the SSSC controllers is changed into an optimization problem with a time domain-based objective function.Then, it is solved by using the particle swarm optimization (PSO) algorithm that has a strong ability to find the most optimistic results. Only local and available state variables are used as the input signals of each controller for the decentralized design. Therefore, the designed SSSC controller has a simple and easy-to-implement structure. The performance of the proposed controllers is evaluated for both single-machine infinite-bus (SMIB) power system and multi-machine power system. Then, to show the robustness and effectiveness of proposed design approach, the results are presented over a wide variety of system configurations, loading conditions, and disturbances. Analyzing the results reveals that the designed PSO-based output feedback SSSC damping controller has a strong ability in damping power system oscillations. Furthermore, analyzing system performance under different operating conditions shows that the ψ-based controller is superior to the m-based controllers.

Switching power system stabilizer and its coordination for enhancement of multi-machine power system stability

This paper proposes a coordinated switching power system stabilizer (SPSS) to enhance the stability of multimachine power systems. The SPSS switches between a bang-bang power system stabilizer (BPSS) and a conventional power system stabilizer (CPSS) based on a state-dependent switching strategy. The BPSS is designed as a bang-bang constant funnel controller (BCFC). It is able to provide fast damping of rotor speed oscillations in a bang-bang manner. The closed-loop stability of the power system controlled by the SPSSs and the CPSSs is analyzed. To verify the control performance of the SPSS, simulation studies are carried out in a 4-generator 11-bus power system and the IEEE 16-generator 68-bus power system. The damping ability of the SPSS is evaluated in aspects of small-signal oscillation damping and transient stability enhancement, respectively. Meanwhile, the coordination between different SPSSs and the coordination between the SPSS and the CPSS are investigated therein.

Design of Power System Stabilizer (PSS) to Enhance Power System Stability in Power System

Design of Power System Stabilizer (PSS) to Enhance Power System Stability in Power System