Multi-machine System Research Articles

Optimal Localization of Distributed Generator (Dg) in Multi Machine Systems

Evolution to a sustainable power environment consequences in aggregated originator and load dynamics in the distribution network. State estimation is a key characteristic in construct ok community fashions for online monitoring and analyzes. The requirements of distribution device kingdom estimation (DSSE) is becoming rigorous because of the wishes of recent gadget modeling and function practices associated with integration of allotted electricity sources and the adoption of better technologies in distribution network. This paper summarizes the most recent technology, predominant hurdles, and challenges in DSSE expansion. The possibilities, paradigm shift, and future study directions that might facilitate the want of DSSE are discussed.

PSS Parameter Optimization Based on Comprehensive Damping Effect Method Aiming at Actual Grid Characteristics in Northern China

In this paper, we proposed the comprehensive damping effect method to optimize the PSS parameters. Different from other studies, the optimization in this paper is based on both the amplitude-frequency and the phase-frequency properties, while other studies mainly focus on the phase-frequency characteristics. The actual grid data in Northern China are employed to verify the optimization effect in the multimachine system. The proposed method is compared with the engineering method, the existing optimization method, and the commercial software. The comparison shows that the PSS parameters obtained by the proposed method in this paper are superior to those obtained by the engineering experience, the phase-frequency optimization method, and the commercial software. In the cases of different phase-frequency range requirements, the wider the phase-frequency range is, the better the damping effect of the obtained parameters will be.

Comprehensive Power System Stability Improvement with ROCOF Controlled SMES

In order to mitigate most power quality issues in renewable power penetrated systems, load frequency control in automatic generation control based power systems and transient stability concerns in any power system, the deviation in frequency at the point of common coupling is chosen as the driving input for SMES active power control (Δf-control). We report a rate of change of frequency (ROCOF) controlled SMES as a resilient damping device to counter exogenous uncertainties in a wind based multi machine system. Primarily, the ROCOF is contingent on the active power mismatch. SMES reference active power command is issued using a genetic algorithm tuned scheme, participating through ROCOF measurement. The non linear action of SMES is realized by controlling the converter firing angles by a smooth four-zone operation, thus determining the voltage applied across the superconducting inductor. While preserving the dynamics of the DC link and supervising the state of charge (SoC) of the inductor, the effectiveness of the aforementioned control strategy is authenticated by performing non-linear simulations in MATLAB/Simulink. In addition, the dominant modes are also tracked and it is found that the percentage increase in aggregate damping ratio is around 133% using the proposed ROCOF-SMES control.

Mathematical modelling and application of generalized unified power flow controller (GUPFC) steady state model for power system network

Unified power flow controller (UPFC) is a unique kind of flexible alternating current transmission system device which can adjust power system parameters like active power, reactive power, and voltage magnitude as well as phase angle. Power transmission network is going to be more and more complex because of increase in multi-machine systems. In multi-machine systems, there is a need to adjust the power system parameters of two or more bus. In such cases, power system requirements are achieved by multiple UPFC. A reformed form of unified power flow controller which is defined as generalized UPFC comprises of one shunt converter and one then one series converter. Generalized UPFC is able to adjust the power system parameters for two or more bus or a subsystem. This paper provides the mathematical modeling of generalized UPFC in details. A novel approach based on a controlled current source employed for the scheming of phasor model of generalized UPFC in MATLAB. A comprehensive assessment is done between a phasor generalized UPFC model and multiple UPFC for congestion management of power system. The results establish the supremacy of generalized UPFC over multiple UPFC. This is the only work that brings forth for the first time, the time scheming of the phasor model of GUPFC in MATLAB/ Simulink.

A continuous mitigation of kVAR-voltage problem of hybrid isolated power system using UPFC

Electric power system in rural India is in growing stage but still many parts of country are not connected. Renewable Energy Sources (RES) based small power system can be beneficial for such locations. The fluctuations associated with renewable energy sources can be countered by Flexible AC transmission Systems (FACTS) devices. In this paper, Unified Power Flexible controller is used for studying the kVAR-voltage problem of test system. The proposed test system is a combination of conventional alternator and asynchronous generator representing diesel and wind energy system machines. A time-domain simulations is done in the proposed system considering variable speed conditions. This paper clearly presents the voltage-kVAR management capabilities of this controller. The detailed analysis of proposed multi-machine test system with UPFC has been done in SIM POWER SYSTEM/MATLAB software

Frequency Oscillation Analysis of Power System With Multiple Governor Deadbands

In recent years, the ultra-low frequency oscillation of power system is one of the most concerned frequency stability problem. The governor deadband are considered as one of the main influences. However, the existing methods can only deal with single deadband segment. As for a multi-machine system with multiple deadband segments, it lacks the analysis method for frequency oscillation. To solve this problem, this paper first define the extended description function applied to nonlinear composite system according to the principle of traditional description function method. The extended description function can quantify the relationship of input and output of a system with multiple nonlinear segments. Then, based on the uniform frequency model of multiple governors, the turbines and governors of hydro and thermal power units with different deadband widths are equivalent to one extended description function. The locus of minus reciprocal of the extended description function with oscillation amplitude and the Nyquist curve of the generator are plotted on the complex plane for the analysis of system stability. Next, the critical oscillation amplitude of disturbance to trigger the system frequency oscillation is calculated according to the point of intersection of both curves. Finally, the simulation results show that the critical oscillation amplitude can reflect the stability of system. The change of deadband width is positively correlated with the critical oscillation amplitude. The appropriate setting of deadband and configuration of hydro-thermal generation are effective measures to suppress the ultra-low frequency oscillation while retain the ability of frequency regulation.

Stability improvement on industrial load using current controlled voltage regulator

In this paper, we considered an industrial load with 33 bus system. This system introduces the modeling of the Current Controlled Voltage Regulator in the load flow calculations for steady-state voltage compensation and loss reduction. Here the performance of the system involves the various ranges of maximum capacity and modeling of this system in its maximum rating of reactive power injection is derived. During this analysis, the proposed fuzzy expert system, generator speed deviation, and its derivative are chosen as input signals to fuzzy logic based power system stabilizer. In this approach centers of membership functions and the parameters of the fuzzy logic controllers have been tuned using a genetic algorithm. Inclusion of GA in tuning fuzzy logic based power system stabilizer will provide good damping and significantly reduces computational time in the design process. Simulation results on a multimachine system subjected to small perturbation and three-phase fault show the effectiveness and robustness of the proposed PSS over a wide range of operating conditions and system configurations.

Problems and challenges of power-electronic-based power system stability: A case study of transient stability comparison

With the development of power electronic technology and requirement for clean energy, the traditional power systems which are dominated by synchronous generators are gradually changing into the power-electronic-based power systems with diversified power electronic equipment. The power systems are facing a great revolution in their primary equipment, and this has not happened in the past one hundred years. In recent years, with great increasing penetration of power electronic devices into power grids, the large-scale blackouts caused by power electronic devices have been reported, which seriously threatens the safe and stable operation of power systems. Under the above background, in this paper we first introduce several methods of analyzing the traditional power system transient stability from the equal area criterion for the single machine infinite bus system to several Lyapunov function based direct methods for multi-machine systems. Then we introduce some of our recent work on the nonlinear modeling and analysis of a key component of power-electronic-based power systems, voltage source converter (VSC), and propose a multiple machine system model including power electronic equipment and traditional synchronous machines. Finally, we illustrate the transient characteristics of the power electronic devices, and summarize the basic problems and challenges for the transient stability of power-electronic-based power systems. We hope that these basic problems in power-electronic-based power system dynamics including nonlinearity, multi-time-scale, and complexity could arouse the general interest of researchers in the fields of complex systems and statistical mechanics.

Modelling and simulation of a multi-machine power system incorporating power system stabilisers and static VAR compensators for transient stability enhancement

This paper presents a model of a multi-machine system and examines the efficacy of power system stabilisers and static VAR compensator in transient stability enhancement. The main contribution of this work is a compact, user-friendly and comprehensive model to analyse and reinforce the system stability through a coordinated focus on damping of electromechanical oscillations and suppression of voltage deviations. The model is developed by integration of various mathematical equations pertaining to synchronous machines and some network equations. To test the effectiveness of the proposed model, MATLAB-based simulations are carried out by subjecting the system to challenging transients. The performance evaluation of the model incorporating both power system stabilisers and static VAR compensator is tested against the individual performance of each. It is found that the model is effective in maintaining transient stability as well as improving transient stability limits.

Повышение эффективности стабилизации режима при возмущениях в энергосистеме

The stability of the parallel operation of the generators in the power system is ensured by automatic excitation controllers (AEC). In case of disturbances in the power system and the frequency drop at the generator, the AEC provides a controlled signal to reduce excitation, which leads to a decrease in the braking electromagnetic moment on the shaft and provides acceleration of the generators, and when the frequency increases, a signal is sent to increase the excitation, which increases the braking moment. Obviously, this can only be effective if the phase deviation of the frequency at the terminals of the stator coincides with the frequency of rotation of the shaft of the generator. However, in parallel operation of numerous generators in a complex multi-machine system with strong electrical connections, the amplitude and phase of the deviations of the frequency of the generator can differ significantly from the amplitude and phase of the deviations of the frequency of rotation of its shaft. It is fundamentally impossible to compensate for this difference by choosing the gain and time constants of the elements of the control channels, since this difference varies depending on the number of units operating in parallel, the degree of their connection in the power system, and other dynamically changing factors. The phase shift of the signals with respect to the deviation and the frequency derivative can lead instead to increase of the oscillations, in amplitude and time. The paper discusses a method of stabilizing the modes by the difference between the rotational speed of the generator shaft and the voltage frequency on busbars of power plants. The results of full-scale system tests carried out to verify the effectiveness of this method are presented, which confirmed transient processes improvement. Suggestions for using the proposed stabilization method are provided.

Fault clearance in Nine-Bus system using Custom Power Devices

The power transfer capability of a system determines the power quality and the reliability of the power system. The transmission side of the power system is of different configuration. This paper involves the modeling of a three-phase multi-machine system with nine bus configurations. The system is subjected to different fault conditions. The system is modeled with the help of MATLAB- Simulink. The power quality of the system is analyzed. The system active and the reactive power can be compensated by the FACTS devices. The FACTS devices are power compensating devices that play a vital role in increasing the power quality of the system. The three-phase multi-machine system is integrated with the FACTS devices like STATCOM and UPFC and different parameters where analyzed.

Transient Stability Improvement using Resistive-type Superconducting Fault Current Limiters (R-SFCL)

The rapid growth in the demand for electrical energy due to the astronomic growth in population has led to increase in the system fault current levels. This increase in fault current if not properly checked, could lead to system collapse. Superconducting Fault Current Limiters (SFCLs) are used in power system networks to mitigate against high fault current levels. In this study, the transient stability enhancement capability of three commercially available Resistive-type Superconducting Fault Current Limiters (R-SFCLs) based on Yttrium-Barium-Copper-Oxide (YBCO) and Bismuth-Strontium-Calcium-Copper-Oxide (BSCCO) Coated Conductors of different lengths were simulated. The test case was the Nigeria 330kV transmission network. The Runge-Kutta method was used to solve the differential equations characterizing the swing equations of the generators. The proposed method shows the effectiveness of the SFCL in enhancing transient stability of a Multi-Machine System.

RETRACTED: Application of Machine Learning and Big Data in Doubly Fed Induction Generator based Stability Analysis of Multi Machine System using Substantial Transformative Optimization Algorithm

With the increase in the amount of data captured during the manufacturing process, surveillance systems are the most important decision making decisions. Current technologies such as Internet of Things (IoT) can be considered a solution to provide efficient monitoring of productivity. In this study, it has suggested a real-time monitoring system that uses an IoT, big data processing and an Offshore Wind Farm (OWF) model is proposed. The Offshore Wind Farm (OWF) is an extended level invasion in modern power electronics systems, in this proposed work Doubly Fed Induction Generator (DFIG) based multi machined OWF was designed, and power stability was analyzed using Substantial Transformative Optimization Algorithm (STOA). The Voltage Source Converter (VSC) and High Voltage Direct Current (HVDC) system was combined with onshore network. The terminal voltage of onshore network was controlled through Onshore Side Converter (OSC), active and reactive power was regulated separately using VSC. The performance of the onshore network was evaluated under renewable network errors (Total Harmonics distortion and steady state error) beside with OWF. The OWF - DFIG active and reactive power was controlled smoothly with in the limit of HVDC, and the power framework security can be updated by controlling the active power of the OSC to help its terminal voltage using STOA methodology. From the voltage control mode, the electrical faults are recovered rapidly with minimum fluctuation. The dynamic simulation comes about additionally demonstrate that onshore network fault can't impact OWF behind HVDC transmission system. Because of the specialized favorable circumstance, VSC-HVDC innovation, the constancy in OWF is very much ensured against the onshore grid faults. The proposed STOA based system has validated through simulation in Matlab Simulink environment. General, 97% effectiveness, accomplished at full load condition in light of the proposed system. The results showed that the IoT system and the proposed large data processing system were sufficiently competent to monitor the manufacturing process.

Analytical on‐line method of determining transient stability margin using protection information for asymmetric faults

The transient stability margin is affected by different fault locations, fault clearing time and fault types that could be provided by protection information. This study presents an analytical on-line method of determining transient stability margin quantitatively using protection information for multi-generator system. First, the multi-machine system is equivalent to a one-machine infinity-bus system with the help of complementary cluster centre of inertia-relative motion. Second, the asymmetric fault models are built using positive rule, and the transient stability margin is then deduced by modelling the piecewise models of generator angles. Third, the practical transient stability margin assessment algorithm is then obtained. The sensitivity and affection mechanism of stability margin affected by fault factors are further derived, and the analytical stability margin is put forward to online access the transient stability margin after fault with the acquisition of the protection information. Finally, four-generator system, New England system and a real large power grid are used as test systems to verify the effectiveness and accuracy of the proposed method.

Intelligent swarm-based optimization technique for oscillatory stability assessment in power system

<p>This paper discussed the prediction of oscillatory stability condition of the power system using a particle swarm optimization(PSO) technique. Indicators namely synchronizing(<em>K<sub>s</sub></em>)and damping(<em>K<sub>d</sub></em>) torque coefficients is appointed to justify the angle stability condition in a multi-machine system. PSO is proposed and implemented to accelerate the determination of angle stability. The proposed algorithm has been confirmed to be more accurate with lower computation time compared with evolutionary programming(EP) technique. This result also supported with other indicators such as eigenvalues determination, damping ratio and least squares method. As a result, proposed technique is achievable to determine the oscillatory stability problems.</p>

Stability Analysis of Wind Farm Connected Multi Machine System Using Fuzzy Controller Based STATCOM and SVC

Large capacity wind farm are used to fulfil the demand of power now days. Stability of these wind farms is the main concern when integrating with the large power system. FACTS devices are employed with the system to advance the dynamic time responses of the system. In this paper a comparative analysis of STATCOM and SVC has been done. At the place of conventional controllers like P, PI, PID fuzzy logic control (FLC) has been used in the FACTS devices used. These FACTS devices are used to improve the power quality of the overall system. To inspect the system performance and analyze the behavior of the system a three phase to ground fault has been taken into account at two different locations, the software used for modelling and simulation is MATLAB/Simulink. Results demonstrate damping and oscillations of Fuzzy controlled STATCOM and SVC based system.The comparative analysis shows that the system with FLC based STATCOM has better performance than the FLC based SVC and fast fault clearance.

Standard passivity-based control for multi-hydro-turbine governing systems with surge tank

This paper addresses the problem of control design for hydro-turbine governing systems with surge tanks from the perspective of standard passivity-based control. The dynamic model of a synchronous machine is considered in conjunction with a model of the hydro-turbine to generate an eleventh-order nonlinear set of differential equations. An Euler–Lagrange representati of the system and its open-loop dynamics is developed. Then, the standard passivity-based control is applied to design a global and asymptotically stable controller in closed-loop operation. The proposed control is decentralized to avoid challenges of communication between the hydro-turbine governing systems. The proposed standard passivity-based control approach is compared with two control approaches. First, a classical standard cascade proportional-integral-derivative controller is applied for the governing system, the automatic voltage regulator, and the excitation system. Second, a sliding mode control is also implemented in the governing system. Two test systems were used to validate the performance of the proposed controller. The first test system is a single machine connected to an infinite bus, and the second test system is the well-known Western System Coordinating Council’s multimachine system. Overall, simulation results show that the proposed controller exhibits a better dynamic response with shorter stabilization times and lower peaks during the transient periods.

Topological analysis of stability regions of power systems considering global orbits

In this paper, the stability region of power systems is studied from a geometrical point of view. A new method is proposed to obtain the global orbits (GOs) which have the significance for making the stability region be more complete. This method is based on the theory of invariant manifolds and focuses on dynamical behavior at infinity. The boundary of the stability region (BSR) with respect to the stable manifolds of dimension-1 and dimension-2 are given to describe the topological characteristics of the stability region of a multi-machine system. The effect of damping coefficient on the stability region is discussed through the variation of the singularities at infinity. The GOs of the power system when subjected to large disturbance are analyzed with the time domain simulation. The validity of the proposed approach is demonstrated on a 16-machine 68-bus system. The simulation results reveal the types and characteristics of the GOs, which play an important role in the prediction of stability/instability of the postfault system.

Comprehensive learning bat algorithm for optimal coordinated tuning of power system stabilizers and static VAR compensator in power systems

This article presents a novel comprehensive learning bat algorithm (CLBAT) for the optimal coordinated design of power system stabilizers (PSSs) and static VAR compensator (SVC) for damping electromechanical oscillations in multi-machine power systems considering a wide range of operating conditions. The CLBAT incorporates a new comprehensive learning strategy (CLS) to improve microbat cooperation; location updating is also improved to maintain the bats’ diversity and to prevent premature convergence through a novel adaptive search strategy based on relative travelled distance. In addition, the proposed elitist learning strategy speeds up convergence during the optimization process and drives the global best solution towards promising regions. The superiority of the CLBAT over other algorithms is demonstrated via several experiments and comparisons through benchmark functions. The developed algorithm ensures convergence speed, credibility, computational resources and optimal tuning of PSSs and SVCs of multi-machine systems under different operating conditions through eigenanalysis, nonlinear simulation and performance indices.

Global Geometric Structure of the Transient Stability Regions of Power Systems

In this paper, a novel qualitative method is proposed to analyze the transient stability of power systems. Unlike the traditional methods, this method can illustrate the structural characteristics of the stability region and display the boundary on the global phase plane intuitively. Particularly, the stability boundary and phase portraits are investigated in three-dimensional space. Global phase portraits including the singularity at infinity (SAI) show the beginning and ending points of the portraits, and indicate the whole situation of an attractor's basin. To properly use the method to clarify the dynamic behavior at infinity, the multi-machine system is simplified by an equivalent method and the trajectories of the rotor angle near the unstable equilibrium point are projected into a closed ball based on the invariant submanifolds. The effects of damping coefficient, fault locations, and fault types on the transient stability region are discussed by the coordinate of the SAI, which are obtained based on the qualitative theory of differential equations. If the traditional generators are replaced with the distributed energy resources, the transient stability of the power system may be affected both positively and negatively. The simulation experiments of the IEEE 39-bus test system are carried out to validate the effectiveness of the proposed method.