Excitation control for improving transient stability limit and voltage regulation with dynamic loads

The problem of transient stability and voltage regulation for a single machine infinite bus (SMIB) system is addressed in this paper. An improved Backstepping design method for transient stability enhancement and voltage regulation of power systems is discussed beginning with the classical Backstepping to designing the nonlinear excitation control of synchronous generator. Then a more refined version of this technique will be suggested incorporating the sliding mode control to enhance voltage regulation and transient stability. The proposed method is based on a standard third-order model of a synchronous generator connected to the grid (SMIB system). It is basically implemented on the excitation side of the synchronous generator and compared to the classical Backstepping controller as well as the conventional controllers which are the automatic voltage regulator and the power system stabiliser. Simulation results prove the effectiveness of the proposed method which ameliorates to a great extent the transient stability compared to the other methods.

This study presents the design of intelligent coordinators for the automatic voltage regulator (AVR) and power system stabiliser (PSS) in a multi‐machine power system. The intelligent coordinators are designed to update the gains of AVR and PSS in severe disturbances to guarantee the stability of the studied power system. Three potent intelligent coordinators are proposed: (a) fuzzy logic coordinator, (b) artificial neural network coordinator, and (c) brain emotional learning coordinator. Since the intelligent coordinators are based on the knowledge of the experts, desirable scaling factors are considered in the output signals of the coordinators to achieve optimal results. The scaling factors are optimised using a new evolutionary approach known as the sine–cosine algorithm. To evaluate the efficiency of the proposed intelligent approaches, the performances of coordinators are analysed on a two‐area four‐machine power system. A range of power system signals, such as rotor speed, terminal voltages, acceleration power and rotor angle of generators are demonstrated to approve and compare the performance of the intelligent coordinators. The simulation results indicate that the intelligent coordinators can guarantee the stability of the power system and satisfy performance objectives, such as desired transient and steady‐state errors.

The stability of the electric power system is very important, because the stability of the system affects the quality and reliability of electrical energy supply. Many things can affect the stability of the system, one of which is a dynamic load that affects dynamic stability, dynamic stability can be defined as the system's ability to remain in synchronous conditions after the first swing (transient period) until the system reaches steady state condition, a power system is said to be in stable when all variables are stable, both bus voltage, rotor angle and generator rotor rotational speed. In this study the authors used the automatic voltage regulator (AVR) and power system stabilizer (PSS) controls to control the system's dynamic stability, hoping that after installation of these additional control devices the dynamic stability of the power system could be improved so that the system remained stable despite disturbances or load changes . Then a power system simulation was carried out using the MATLAB 2008a program, which proved that the installation of a power system stabilizer can reduce oscillation, in this case PSS works as an electric power controller or reactive power can be seen from the output voltage which only has overshoot 1.0169 before a load change and after being given a load change with the input step 25 overshoot increasing only 1.0215 for output the speed and angle of the generator rotor is less influential.

This paper presents the nonlinear design of excitation controller and power system stabilizer (PSS) aimed at ensuring transient stability and satisfactory post-fault voltage regulation following a large disturbance. The proposed design offers the possibility to select the PSS gains so as to achieve both swings damping in an assigned time interval and desired attenuation of disturbances arising from the excitation control loop. As concerns the excitation controller design it is based on the nonlinear compensation technique and ensures a quick sustainment of the regulated voltage after that the fault is cleared. Simulation results carried-out on a four-nodes power system model show the goodness of the proposed design methodology with a reference to a severe large disturbance represented by a three-phase short-circuit near the generator terminals.

Automatic voltage regulator (AVR) systems are critically required in many systems such as hydro, gas, steam turbines and engines. Effective control of an AVR system is complex and challenging due to its unstable open loop response characteristics. The AVR system is required to sustain appropriate voltage levels in spite of fluctuations in the main supply. Hence, the AVR system needs to be primarily designed for stability. This paper presents design implementation of the first and second generations of CRONE controllers (Commande Robuste d'Ordre Non Entier) for an AVR system. CRONE is a non-integer order robust controller which is far more effective than the standard PID controllers as it offers better tuning and flexibility in controlling the AVR process. In the present study, various time-domain performance criteria with and without controller were simulated to validate the accomplishment of AVR CRONE controllers. The proposed control procedure for enhancing AVR systems' efficiency has been shown to be effective and better in terms of improved phase and gain margins.

This paper presents the modelling and simulation of Centurion electric power system using MATLAB/SIMULINK package. The basic system is tested under large and small disturbances to study the dynamic behaviour of the system and the stability margins associated with the different configurations of the system. The single-machine infinite bus (SMIB) power system model is considered, with the synchronous generator being represented by model 1 with both the generator main field winding and the damper winding in q-axis, and developed to evaluate the impact of power system stabilizer (PSS) with automatic voltage regulator (AVR) and flexible ac transmission system (FACTS) based controllers on power system stability. As a suggested solution to increase stability margins of the system, PSS with AVR are installed in the network. FACTS controllers are added, modelled and tested to validate the effectiveness on the different stability margins under both large and small disturbances.

Introduction. In an electrical power system, the output of the synchronous generators varies due to disturbances or sudden load changes. These variations in output severely affect power system stability and power quality. The synchronous generator is equipped with an automatic voltage regulator to maintain its terminal voltage at rated voltage. Several control techniques utilized to improve the response of the automatic voltage regulator system, however, proportional integral derivative (PID) controller is the most frequently used controller but its parameters require optimization. Novelty. In this paper, the chaotic sequence based on the logistic map is hybridized with particle swarm optimization to find the optimal parameters of the PID for the automatic voltage regulator system. The logistic map chaotic sequence-based initialization and global best selection enable the algorithm to escape from local minima stagnation and improve its convergence rate resulting in best optimal parameters. Purpose. The main objective of the proposed approach is to improve the transient response of the automatic voltage regulator system by minimizing the maximum overshoot, settling time, rise time, and peak time values of the terminal voltage, and eliminating the steady-state error. Methods. In the process of parameter tuning, the Chaotic particle swarm optimization technique was run several times through the proposed hybrid objective function, which accommodates the advantages of the two most commonly used objective functions with a minimum number of iterations, and an optimal PID gain value was found. The proposed algorithm is compared with current metaheuristic algorithms including conventional particle swarm optimization, improved kidney algorithm, and others. Results. For performance evaluation, the characteristics of the integral of time multiplied squared error and Zwe-Lee Gaing objective functions are combined. Furthermore, the time-domain analysis, frequency-domain analysis, and robustness analysis are carried out to show the better performance of the proposed algorithm. The result shows that automatic voltage regulator tuned with the chaotic particle swarm optimization based PID yield improvement in overshoot, settling time, and function value of 14.41 %, 37.91 %, 1.73 % over recently proposed IKA, and 43.55 %, 44.5 %, 16.67 % over conventional particle swarm optimization algorithms. The improvement in transient response further improves the automatic voltage regulator system stability for electrical power systems.

The quality of power system operating need to assess maturity of small oscillation stability issues of regional power grid thoroughly, analysis level of operating, controller installation allocating and parameter optimization scheme from different develop stage of regional power grid accurately. The assessment scheme is based on damping torque analysis of real large scale power system. Small oscillation stability is to be evaluated through the mechanism of damping torque analysis with automatic voltage regulator and other power system stabilizers. By analyzing the characteristic of the link between damping torque provided or transferred through each generator and the oscillation mode detected in the power system, the maturity indice has been established. This indice may cover the information of the contribution of controllers towards the power system and the dispatching within each generator in power system. Practical application effects in a real large scale power grid indicates this assessment can thoroughly describe the action of control elements in the power grid, help to depict the whole picture of impact applying power system controllers. A novel maturity evaluation of small oscillation in power grid is presented.

The large-scale integration of doubly-fed induction generator (DFIG) based wind power plants poses stability challenges for power system operation. This study investigates the transient stability and dynamic performance of a modified 3-machine, 9-bus Western System Coordinating Council (WSCC) system. The investigation was conducted by connecting the DFIG wind farm to the sixth bus via a low-impedance transmission line and installing power system stabilizers (PSSs) on all automatic voltage regulators (AVRs). A three-phase fault simulation was carried out to test the system, with and without power system stabilizers and a static synchronous compensator (STATCOM) device. Time-domain simulations demonstrate improved transient response with PSS-STATCOM control. A 50% reduction in settling time and 70% decrease in power angle undershoots at the slack bus are achieved following disturbances, even at minimum wind penetration levels. Load flow analysis shows the coordinated controllers maintain voltages within 0.5% of nominal at 60% wind penetration, while voltages at load buses can deviate up to 15% without control. Eigenvalue analysis indicates the PSS-STATCOM boosts damping ratios of critical oscillatory modes from nearly 0% to over 30% under high wind injection. Together, the present findings provide significant evidence that PSS and STATCOM cooperation enhances dynamic voltage regulation, angle stability, and damping across operating ranges, thereby maintaining secure operation in systems with high renewable integration.

With the development of science and technology, the cost of offshore wind power development and transmission has gradually decreased, making offshore wind power technology a research hotspot. The installed capacity has been increasing year by year. China has abundant offshore wind energy resources, which are much richer than those on land and are available for exploitation. Offshore wind speeds are stable and do not produce harmful substances. Therefore, studying the transient voltage stability of offshore wind power grid-connected systems to improve the utilization efficiency of offshore wind power and protect the ecological environment is critical. After large-scale wind power is connected to the grid, ensuring the stability of the system's transient voltage becomes crucial. This paper aims to deeply study the transient voltage stability of offshore wind farm grid-connected systems, providing theoretical support for the subsequent design and operation of offshore wind farms. A simulation model of a typical power system integrated with offshore wind farms was established using PSAT. Relevant transient voltage stability indices were calculated, and the impact of varying wind speeds on the transient voltage stability of the grid-connected system was investigated. Static Var Compensators (SVC) and Static Synchronous Compensators (STATCOM) were installed for comparative analysis. The results demonstrate that excessively low wind speeds degrade the system's transient stability, and the installation of SVC provides superior improvement in transient voltage stability compared to STATCOM.

The proportional-integral-derivative(PID) controllers in the process plants like thermal power plants, biomedical instrumentation is of popular use. The priority of such controllers is obviously a fine tuning as a high degree of industrial expertise is required for any other alternative. So in order to get the best results of PID controllers the optimal tuning of PID gains are required. This paper presents the design and performance analysis of proportional integral derivative (PID) controller for the Automatic Voltage Regulator (AVR) system using multi objective non dominated sorting genetic algorithm-II(NSGA-II). It is required to develop the electronic control system for the synchronous generator for the stable operation of power system. The Automatic Voltage Regulator (AVR) is widely used in electrical power field to obtain the stability and good regulation of the electric system. The characteristics of alternator output required are constant voltage and constant current. To get the constant output, alternator field excitation is controlled by Automatic Voltage Regulator (AVR). The Automatic Voltage Regulator maintains the constant voltage up to certain level of load current independently of generator speed and load. This paper further deals with the robustness analysis of the AVR system tuned by NSGA-II algorithm is performed by varying the time constants of amplifier, exciter, generator and sensor in the range of-50% to +50% insteps of +25%.

Recently, automatic voltage regulator and power system stabilizer are widely used in the power system in China. However, the effectiveness of damping control is restricted by voltage control, which will lead to oscillation in exciter circuit when the gain of controllers reaches a certain value. To coordinate two controllers, the mechanism of oscillation in exciter circuit is reveal first, after that the relationship gain of two controllers is analyzed to illustrate the contradictory of voltage control and damping control, then a coordinated voltage and damping control method of synchronous generator is proposed. Finally, the correctness of the mechanism and proposed method is testified on two-machine system and four- machine system.

An improved RUN optimizer based real PID plus second-order derivative controller design as a novel method to enhance transient response and robustness of an automatic voltage regulator

In this paper, a real-valued genetic algorithm (RGA) and a particle swarm optimization (PSO) algorithm with a new fitness function method are proposed to design a PID controller for the Automatic Voltage Regulator (AVR) system. The proposed fitness function can let the RGA and PSO algorithm search a high-quality solution effectively and improve the transient response of the controlled system. The proposed algorithms are applied in the PID controller design for the AVR system. Some simulation and comparison results are presented. We can see that the proposed RGA and PSO algorithm with this new fitness function can find a PID control parameter set effectively so that the controlled AVR system has a better control performance.

This paper presents a method for robust optimum tuning of Fractional-order Proportional Integral Derivative (FoPID) controller for Automatic Voltage Regulator (AVR) system. Optimal tuning of FoPID parameters for AVR system are accomplished by using Salp Swarm Algorithm (SSA) of optimization. The performance of the AVR system with FoPID controller tuned by SSA shows the robust performance against disturbances deliberated at the output of the system. To test the robustness of the system, in the presence of external disturbance $H_{\infty}$ norm is considered. AVR system with SSA tuned PID controller is also simulated with MATLAB platform. Results shows that the AVR system with SSA tuned FoPID controller outperform the SSA tuned PID controller in the presence of external disturbances at output of the system and shows its disturbance rejection capabilities.