Multi-machine System Research Articles

Modelling and analysis of small signal for multi-machine parallel system based on droop control

Modelling and analysis of small signal for multi-machine parallel system based on droop control

Optimal design of controllers for power network connected SOFC using of multi-objective PSO

In this paper, we study the concept and forming manner of Solid Oxide Fuel Cell (SOFC) into the electrical system and then, its effect on small signal stability is investigated. The paper illustrates the essential module, mathematical analysis and small signal modeling of the SOFC joined to single machine system. The aim of this study is to reduce power oscillations in the presence of the SOFC with optimal stabilizer. The multi-objective Particle Swarm Optimization (MOPSO) technique has been used for designing a Power System Stabilizer (PSS) in order to improve the performance of the system. Two objective functions are regarded for the design of PSS parameters in order to maximize the damping factor and the damping ratio of the system. To evaluate the efficiency of the proposed optimal stabilizers, four scenarios are considered and then, its results have been analyzed. The proposed PSS tuning technique can be applied to a multi-machine system connected to the SOFC. The efficiency of MOPSO based proposed PSS on the oscillations the system related to SOFC is illustrated by time-domain simulation and also, the comparison of the MOPSO based proposed PSS with the PSS based-single objective method has been prepared.

Transient Stability Assessment Using Individual Machine Equal Area Criterion PART I: Unity Principle

Analyzing the system trajectory from the perspective of individual machines provides a distinctive approach for the analysis of the transient stability of power systems. These two-paper series propose a direct-time-domain method that is based on the individual-machine equal area criterion. In the first paper, by examining the mapping between the trajectory and power-vs-angle curve of an individual machine, the stability property that characterizes a critical machine is elucidated. The mapping between the system trajectory and the individual-machine equal area criterion is established. Furthermore, a unity principle between the individual-machine stability and system stability is proposed. It is proved that the instability of the system can be confirmed by finding any one unstable critical machine, enabling the monitoring of the transient stability of a multimachine system in an individual-machine manner in transient stability assessment.

Result of Analysis of Power System Oscillation Damping & Voltage Stability Improvement Using SSSC in A Multi-Machine System

Result of Analysis of Power System Oscillation Damping & Voltage Stability Improvement Using SSSC in A Multi-Machine System

Design of firefly power system stabilizer for stability improvement of multi machine system under contingency

Design of firefly power system stabilizer for stability improvement of multi machine system under contingency

Improving Transient Stability in Power Systems by Using Fuzzy Logic Controlled SVC

<span>This paper presents the capability of a fuzzy logic based stabilizer used for generating the supplementary control signal to voltage regulator of static VAR compensator (SVC) for improving damping oscillations in power systems. Generator speed deviation and line active power were chosen as input signals for the fuzzy logic controller (FLC). The quantity of reactive power supplied/absorbed by SVC is determined based on the two input signal and deviation of terminal voltage at each sampling time. The effectiveness and feasibility of the proposed control is demonstrated with Single Machine Infinite Bus (SMIB) system and multi machine system which show improvement over the use of a fixed parameter controller. It has been observed that a robust controller is obtained with fuzzy logic controller.</span>

Robust fault estimation observer in the finite frequency domain for descriptor systems

ABSTRACTThis paper considers robust fault estimation in the finite frequency domain for linear continuous-time descriptor systems. Based on state augmentation, we propose a fault estimation observer with a non-singular structure. To attenuate the effect of unknown disturbance and fault variation on fault estimation, a fault estimation observer is designed in the finite frequency domain using H∞ optimisation technique. With the design conditions formulated as a set of linear matrix inequalities, the presented fault estimation observer can be efficiently designed. The applicability of the proposed method is verified by numerical simulations of a multi-machine infinite bus system.

Generator governing system based on grey prediction and extension control

To improve the performance of the governing system as well as the stability of the power system, the authors propose grey prediction extension control (GPEC) in the design of generator governing system. Comparing with the conventional control strategy such as conventional proportional–integral–derivative control and simple extension control, GPEC is more suitable for the complex, huge-dimension and time-varying modern power systems. Both a simple hydropower system and a typical multi-machine system are studied, respectively. The simulation results indicate that the proposed GPEC governor controller performs better in reducing overshoot and adjusting time with superiority in leading the system into a stable state.

Transient Stability Enhancement by Optimal Location and Tuning of STATCOM using Biogeography based Optimization Technique

In this paper, transient stability of a multi machine system is evaluated when the system is experienced a three phase fault and the stability of multi machine system is recovered via optimal placement and tuning of STATCOM. Here, the parameters of the STATCOM are tuned by Biogeography based optimization and the STATCOM is positioned optimally in the system. The performance of the tuned system is compared with various operational conditions like without STATCOM, with STATCOM (untuned) and with two STATCOM (untuned). The time domain simulations and the analysis of the multi machine system are done by PSAT (Power System Analysis Toolbox). When the multi machine system is subjected to a three phase fault, voltage stability of the system is collapsed. The multi machine system with STATCOM (tuned by Biogeography based optimization) regains the stability and gives better voltage profile than the system with STATCOM (untuned), with two STATCOM (untuned) and the system without STATCOM. The results are evaluated with the other operational conditions of the system and it proves that the system has the transient stability when the STATCOM (tuned by Biogeography based optimization) is applied.

Distributed Coordinated Control of Offshore Doubly Fed Wind Turbine Groups Based on the Hamiltonian Energy Method

To support doubly fed wind turbine (DFWT) groups in offshore wind farms, this paper proposes a distributed coordinated control based on the Hamiltonian energy theory. This strategy provides global stability to closed-loop systems and facilitates output synchronization. First, a model of a DFWT is realized as a port-controlled Hamiltonian system with dissipation (PCH-D), and the single-machine model is expanded into a multi-machine model of a wind turbine group. Then, by using the design methodology of distributed Hamiltonian systems, a distributed coordinated control is presented for a multi-machine PCH-D system. Furthermore, to investigate failures in wind turbine groups, they are divided into two cases: the separation of failed machines from the system, and the grid-connected operation of failed machines after a fault. These cases correspond to undirected and directed graphs, respectively. Finally, simulations prove that distributed coordinated control enhances the reliability and autonomy of wind turbine groups in offshore wind farms.

Damping of power system oscillations by a novel DE-GWO optimized dual UPFC controller

This work presents a novel dual optimized controller to damp intra plant and inter area oscillations in power system. The parameters of controllers are tuned by a novel hybrid Differential Evolution-Grey Wolf Optimizer (DE-GWO). The dual optimized controller simultaneously controls two independent variables of UPFC there by maximizing the efficacy of controller and UPFC. The effectiveness of proposed algorithm is justified by testing with standard benchmark functions. The dual controller is applied to single and multi machine system for small signal stability assessment. A broad comparison is performed between single and dual controllers employing other standard algorithms prevailing in recent researches. Different objective functions are verified with this controller and ITAE was found to provide best response and selected here for minimization. The oscillation peaks, settling time and eigen values of system response show that proposed dual controller damps oscillations to a large extent in contrast to other single and dual optimized controllers.

Multi verse optimization (MVO) technique based voltage stability analysis through continuation power flow in IEEE 57 bus

Voltage stability analysis of multi machine system is evaluated through continuation power flow (CPF) in this paper. The performance study of SVC is accomplishd in IEEE 57 bus test system for the enrichment of voltage stability through Power System Analysis tool box (PSAT).When the system undergoes unexpected over loading, it might be voltage collapse. The voltage collapse is main issue which can be a serious result of voltage instability. So the stability is affected. It needs compensation to improve the stability from the disturbances. Here the system is analyzed by CPF to improve the stability. Various operating conditions like without SVC and with SVC tuned by MVO are used to estimate the performance of the proposed procedure. The results show that the system with SVC tuned by MVO gets more flexibility in load side and gives stability than the system without SVC.

Preventive maintenance of a batch production system under time-varying operational condition

This paper proposes a dynamic opportunistic preventive maintenance (PM) strategy for a production system with a time-varying batch production pattern. The operation of such a system is generic in that the operational condition (OC) varies from batch to batch and the information about the next batch can be confirmed only upon the completion of the current batch. To accommodate time-varying OC, a modified imperfect maintenance model is developed to optimise the performance of maintenance actions that can only be performed at batch-shift points. The first study presents a PM policy for a single machine with short-term production plans. Then, a multi-machine system is studied with a goal of developing an optimum dynamic opportunistic PM strategy for a group of machines at batch-shift points. Numerical examples are proceeded to illustrate the proposed maintenance strategy in practice. The result reveals that more cost will be incurred if OC is ignored. Moreover, the proposed opportunistic PM strategy achieves the lowest total cost comparing with other strategies as the system downtime cost and maintenance cost has been jointly minimised.

Research on the Impact of DFIG Virtual Inertia Control on Power System Small-Signal Stability Considering the Phase-Locked Loop

Doubly fed induction generator (DFIG) wind turbines with virtual inertia control are coupled to power system in dynamic characteristics, and the control input of virtual inertia control is directly affected by the tracking ability of phase-locked loop (PLL). Thus, it is urgent to study the impact of DFIG wind turbines with virtual inertia control on power system small-signal stability considering the effects of PLL. First, based on DFIG operation characteristic and control strategy, a small-signal model of interconnected system with DFIG integration considering PLL and virtual inertial control is established. Second, the attenuation time constants of DFIG state variables are calculated, and according to the attenuation speeds of different state variables and the coupling between them, it is found out that PLL and virtual inertia are the main factors that affect the coupling between DFIG and synchronous generators. And then, considering that both PLL and virtual inertia control will affect the oscillation modes of synchronous generators, analytical method is used to reveal system small-signal stability under the joint effects of the two factors quantitatively. Analysis results show that, for DFIG wind turbines with virtual inertial control, PLL affects system damping mainly by affecting the participation of virtual inertia in the system. The smaller the PI parameters of PLL are, the smaller the participation factor of virtual inertia control state variables in the interarea oscillation mode is, and the bigger the electromechanical oscillation mode damping ratio is. Simulation results verify the reasonableness of the established model and the possibility that virtual inertia control may cause system small-signal stability to deteriorate in multimachine system.

Reactualization of a Modified Single Machine to Infinite Bus Model to Multimachine System Steady State Stability Analysis Studies Using Losses Network Concepts and Radial Basis Function Neural Network (RBFNN)

To analyze the stability of each generator, the multimachine system must be changed into a Modified Single Machine to Infinite Bus (M-SMIB ) system. This paper proposes a method to change the multimachine system into a M-SMIB system with an equivalent impedance and an equivalent load by determining the contribution of each generator to a loading value using a simple technique. After the M-SMIB system is obtained, a steady-state stability analysis can be performed on each generator unit. In this paper, the maximum generation value which is the generator steady state stability limit, is determined. The Radial Basis Function Neural Network (RBFNN) is applied to determine the range area of generator steady state stability with the variable load to observe the influence of load variation in the generator steady state stability area. Thus, the area of safe operation of the generator can be directly observed without causing instability of the system. Therefore, the steady state stability limits of each generator unit can be directly determined every time there is a change of loading and recognize the operation limit of each generator during disturbances occurring on the bus. This method will be applied to a 4-bus IEEE system with 2 generators.

Solution to Fault Detection During Power Swing Using Teager–Kaiser Energy Operator

The selectivity property of distance relay is affected due to the operation of power swing blocking element which is used to prevent the false tripping imposed by power swing. Therefore, the fault detection algorithm is required to overcome such type of problems. Further, the fault detection during power swing for a series-compensated line is more challenging as the metal oxide varistor protecting the series capacitor imposes other frequency components and adds transients in the voltage and current signals. To resolve such protection challenges, this paper proposes an integrated approach for fault detection, which is based on Teager–Kaiser energy operators of instantaneous zero sequence voltage (Scheme 1) and phasor of negative sequence current (Scheme 2). Instantaneous zero sequence voltage appears only for unsymmetrical ground faults, and it is not affected by current transformer saturation. Other types of faults such as symmetrical, line-to-line faults are detected by Scheme 2, which is immune to capacitor coupling voltage transformer transients. However, both the schemes cover all fault scenarios. The main advantage of proposed scheme is that it is independent of the threshold. It is also not influenced by voltage and current inversions imposed by series capacitor and can detect the fault within 3 ms. The proposed scheme is validated using voltage and current data obtained by simulating 400 kV, 50 Hz, 9-bus multi-machine system using PSCAD/EMTDC. Further, to validate the proposed scheme in real time, the experiments are also carried out on real-time digital simulator.

Optimal Tuning of PSS Parameter Using HACDE Based on Equivalent SMIB Model

This paper proposesthe optimal tuning of PSS parameter using the Hybrid Adaptive Chaotic Differential Evolution (HACDE) based on equivalent SMIB model in spite of the complex interconnection multi-machine system. The interconnection of power systems has some advantages such as the increase in power system reliability and maximum power transfer but, on the other hand, these interactions make the systems difficult to analyze because it becomes larger and more complex. To simplify the analysis, first the multi-machine system is converted into an equivalent Single Machine to Infinite Bus (SMIB) model which is formed by determining the equivalent impedance obtained from the network reduction method using the losses concept based on power flow tracing. This model is fairlyenough to represent the setting of generator control equipment. Afterward, the PSS parameters is tuned using HACDE optimization methods in the SMIB system. The HACDE method is able to increase the damping of generator oscillation. The PSS tuning by using HACDE is compared with the DE and RD-PSO methods. Based on time domain and ITAE simulation results, the PSS tuned using HACDE gives better damping than by using the other methods.

Core Hybrid Event-B II: Multiple cooperating Hybrid Event-B machines

Hybrid Event-B, initially introduced for single machines to add continuously varying behaviour to discrete change of state in Event-B, is extended to cater for multiple cooperating machines. Multiple machine working is mediated by INTERFACE and PROJECT constructs. The former encapsulates a set of variables, their invariants and initialisations, in a form that several machines can exploit simultaneously. The latter organises the set of cooperating machines and interfaces into a coherent system. Machine instantiation and composition via interfaces are discussed. Machine decomposition is explored in this framework. Multi-machine refinement is described. A hypergraph project architecture is proposed. Two small case studies, on power switching and on the European Train Control System (the latter treated earlier within the single machine formalism), illustrate these mechanisms. The semantics of interacting multi-machine systems is described, and proof obligations that ensure correctness are covered. • Extends single machine Hybrid Event-B, to encompass multiple machine working. • Considers formal semantics. • Considers refinement. • Presents a full suite of multi-machine proof obligations. • Gives a selection of small case studies.

A Method of Remote Multi-Machine Program Update Based on Wi-Fi Wireless LAN and CAN Bus

We provide a remote online program update method for multi-machine control system in distributed industrial control field based on WiFi Wireless LAN and CAN bus in this paper. On this basis to achieve the accurate and efficient update for remote multi-machine.

Comparative Study on the Effectiveness of UPFC and TCSC for Increasing Power Transfer Capability Applied to Non-linear Load Models

<p>In recent years, studies have been investigated the effectiveness of UPFC and TCSC in increasing power transfer capability. However, the effectiveness of these FACTS devices in increasing power transfer capability when the load is non-linear has not been established in a comparative study yet. This paper will explore the steady-state performance of the UPFC and TCSC as impedance compensation models. The effectiveness of both FACTS devices are investigated when they are installed in multi-machine systems with different non-linear load models. Simulation results demonstrate that, upon installing UPFC, more active and reactive powers are received at the sending end bus for different types of non-linear load models. In addition, both active and reactive powers are more sensitive in changing the modulation index of the converters. Furthermore, both the active and reactive powers are less sensitive to the non-linearity of the load model type. However, active and reactive powers in case of installing TCSC are only sensitive in changing the firing angle (α) when it is between 90º to 110º. Therefore, results from this study clearly encourage the effectiveness of UPFC in comparison to TSCS in terms of increasing power transfer capability applied to non-linear load models. </p>