Installation Of Phasor Measurement Units Research Articles

An Effective Approach for the Probabilistic and Deterministic Multistage PMU Placement Using Cuckoo Search: Iran’s National Power System

In recent years, phasor measurement units (PMUs) as vital elements have been widely increased in control, monitoring and protection of power systems. In practice, as the size of a power system is large, it is not possible to install all PMUs over a short period of time mainly due to the financial and technical barriers. One solution would be installing the PMUs over different stages. Accordingly, the paper presents an effective approach for multistage PMU placement (MSPP) in power systems, called dynamic MSPP. Furthermore, since the probabilistic concept of observability reflects a more realistic image of power system observability compared to deterministic ones, this paper, unlike most of the existing MSPP models, investigates the MSPP model in both probabilistic and deterministic frameworks. Compared to the existing approaches and results, the obtained ones in this paper show a considerable improvement in the observability level during PMU installation period. In the proposed approach, PMUs are installed at intermediate stages aimed at maximizing the cumulative network observability in a single optimization process, instead of several subsidiary optimizations in conventional approaches. Briefly, the proposed approach offers a complete search space for the problem, while the existing models lead to limited ones. Moreover, because of the nonlinearity posed by the probabilistic concept of observability as well as the proposed MSPP, cuckoo search optimization algorithm is used to handle the complexity and a new problem encoding/decoding technique for the proposed MSPP is utilized. Eventually, the suggested framework is implemented on different case studies as well as Iranian Transmission Network to reveal the performance of the presented model.

A Priority-Based Multistage PMU Installation Approach for Direct Observability of All Network Buses

The highly precise synchrophasor measurements obtained from the phasor measurement unit (PMU) are important for an effective implementation of a wide-area monitoring, protection, control, and self-healing (WAMPCAS) power system. The overall performance of the WAMPCAS power system can be improved if the PMUs are installed at all the buses in a transmission network. However, the multistage PMU installation is obligatory as PMU installation at all network buses is a matter of large-scale investment. Priority should be given to the important buses during the initial and intermediate stages to obtain relatively better observability. The optimal PMU installation (OPI) should be determined at the preliminary stage to measure the voltage phasors of all buses with the least number of PMUs. To evaluate the OPI problem, an improved binary shuffled frog leaping algorithm (IBSFLA) was proposed for the IEEE 118-bus test system. To enhance the overall performance of the IBSFLA and to obtain possible multiple optimal solutions (MOSs), an improved initialization and similarity-checking assessment were developed. A bus-observability maximization was mathematically modeled to select the best solution from MOSs, and the efficacy of the proposed algorithm was verified by comparing its performance with other algorithms.

Distributed State Estimation for Distribution Network with Phasor Measurement Units Information

As the distribution network structure becomes increasingly complex, this paper proposes a distributed state estimation for distribution network with phasor measurement units (PMUs) information to improve the performance of state estimation. This proposed method takes the PMU installation locations as alternative points of the partition, and takes the scale of sub-zone, the number of real-time measurement, and the DG configuration position as the partition criteria, and then conducts distributed state estimation. During the state estimation, the root bus voltage and branch current are used as state variables to reserve the advantage of measurement conversion technology, and the traditional measurement data and PMU measurement data are converted into corresponding currents, which simplifies the Jacobian matrix, thereby reducing iterations and improving the calculation speed of state estimation. Finally, the IEEE 69-bus radial distribution network is used to verify the effectiveness of the proposed method.

A modified optimal PMU placement problem formulation considering channel limits under various contingencies

Phasor measurement units (PMU) are populating the electricity grids throughout the world rapidly due to their wide range of benefits and applications. The traditional optimal PMU placement (OPP) formulations ensure complete network observability with a minimum number of PMU installation. Most of them disregard the PMU channel limitations, the existence of passive measurements/zero injection buses (ZIB), and enhancement of measurement redundancy. This paper presents a modified and effective OPP formulation considering various contingencies and constraints aiming at minimizing the required number of PMU installation and achieving the maximum number of measurement redundancy subjected to complete network observability. The availability of channels per PMU and the presence of ZIB are also taken into account. Besides, the vulnerability of the PMU along with the possibility of line outages is also considered. The formulated OPP problem is tested on five IEEE test networks employing constriction factor particle swarm optimization (CF-PSO). The proposed formulation effectively ensures complete network observability with the installation of a minimal number of PMU. Furthermore, the obtained results prove the efficacy and superiority of the CF-PSO approach over the mixed integer linear programming (MILP) approach and the reported methodologies in literature in terms of achieved measurement redundancies through the installation of less or same number of PMU. Finally, this research applies the proposed OPP formulation on a large-scale electric network of three different scenarios to justify its’ applicability, scalability, and robustness.

Q-Learning-Based Damping Control of Wide-Area Power Systems Under Cyber Uncertainties

The installation of phasor measurement units brings about system-wide synchronized real-time measurements, which makes advanced closed-loop control of wide-area power systems (WAPSs) possible. In addition to uncertainties with the physical system, network imperfections are also critical for control performance and even stability of the system. This paper targets at wide-area damping control of WAPS under both physical and cyber uncertainties. The cyber uncertainties addressed in this paper include both communication delay and package dropout. First, a linearized WAPS model is developed with considerations of random control signal arrivals. Then, a ${\boldsymbol Q}$ -learning-based control algorithm is designed to learn the optimal control under both physical and cyber uncertainties. Finally, to further counteract the communication uncertainties between the control center and actuators, a novel control law is designed based on the statistical analysis to make the long-term control performance approach that under ideal communications. The designed control algorithm is tested with both simplified linear model and detailed nonlinear model of WAPSs. Simulation results demonstrate the effectiveness of the designed algorithm.

Wide-Area Measurement—Based Model-Free Approach for Online Power System Transient Stability Assessment

Online assessment of transient stability of power systems is critical for avoiding blackout. The increasing installation of phasor measurement units in power systems and the advancement of the wide-area measurement systems make it possible to develop methods for online assessment of power systems by using a large amount of real-time synchronous data. In this paper, we propose an approach based on the largest Lyapunov exponent (LLE) for online transient rotor angle stability assessment, using only wide-area measurement systems data. Through establishing a mathematical model that accounts for the LLE value and the rotor speed, as well as analyzing the post-fault phase-plane trajectory, we present a fast stability criterion to determine whether transient instability occurs. The proposed approach is model-free and does not need long-time LLE data to identify the final sign of the LLE. Furthermore, to reduce computational cost and realize online assessment for large-scale power systems, the critical generator pair (CGP) is recognized as the observation for the rotor angle stability assessment, and an effective algorithm for identifying the CGP is presented. Several case studies on the IEEE-39 bus test system and East China power grid are reported to demonstrate the accuracy and effectiveness of the proposed approach.

Power system observability with minimum phasor measurement units placement

This paper presents optimal phasor measurement units (PMUs) placement algorithms for power system observability. The optimal placement problem (OPP) is formulated such that minimizing the number of PMU installations for full networkobservability. Three approaches, in this paper, are introduced aiming at reducing the computational burden in Optimal Placement problems. Depth First Search, Simulated Annealing and Minimum Spanning Tree as well as their differences and relations are discussed in details. The OPP methodologies applied include the system observablility during normal operating conditions, as well as during single branch forced outages. In order to improve the speed of convergence, an initial PMU placement is provided by graph-theoretic procedure. The IEEE 14-bus, 118-bus standard test power systems and New England 39-bus test systems are used for simulation purposes.Keywords: Phasor Measurement Unit (PMU); Observability; Depth First Search; Simulated Annealing Method; Minimum Spanning Tree; Optimal PMU Placement (OPP)

Weak Bus-Oriented Installation of Phasor Measurement Unit for Power Network Observability

AbstractPhasor measurement unit (PMU) is a GPS-based monitoring equipment employed for the improvement of the stability and reliability of the electrical grid. In this work, an optimal PMU placement has been considered to utilize the least number of units in order to make the power network fully observable. Further, this article also suggests to not only determine the minimal number and optimal locations of PMUs but also installation of the maximum number of PMUs on the weakest bus in an electrical network. Thus, the weak bus based on line stability index utilizing load flow measurement is determined. Then a novel numerical methodology which depends upon binary integer linear programming, constrained by weak bus measurement is proposed in this paper. Also, the effect of a single PMU loss considering weak buses is shown. The developed approach has been conducted on standard IEEE -14, -118, -300 and New England 39- bus test systems. Finally, obtained results and comparison with different weak bus methodologies are shown and examined.

PMU-based power system analysis of a medium-voltage distribution grid

The installation of phasor measurement units (PMUs) by Enduris, one of the distribution network operators in the Netherlands to monitor their 50 kV ring distribution grid has resulted in increased observability of the power flows and voltages. However, with the increased observability, there is a need to analyse the distribution grid based on the data generated by the PMU monitoring system. This study provides steady-state and dynamic analysis of the 50 kV Enduris ring distribution grid in terms of voltage and power flow behaviour based on the real-time data acquired from the PMUs. First, the Enduris 50 kV distribution grid under study is modelled in PowerFactory software. This model is subsequently used for analysis of the distribution grid behaviour for two contingencies. The contingencies are actual grid events observed by the PMUs, and using this data, the contingencies are simulated and analysed. The analysis results of each contingency are compared with the data from the PMU monitoring system.

Application of WAMS and SCADA Data to Online Modeling of Series-Compensated Transmission Lines

Transmission line parameters are indispensable prerequisites for power system studies such as power flow analysis, state estimation, congestion management, protective relaying, etc. Since the line parameters vary in time due to various reasons such as environmental condition changes, online estimation of line parameters is thus crucial to assure reliable outcome of system studies. Phasor measurement units (PMUs), as the basis of measurement infrastructure in a smart transmission grid, turn out the online estimation of transmission line parameters feasible. In this paper, a practical method for online estimation of series-compensated transmission lines parameters is devised in which PMU and supervisory control and data acquisition data are jointly used. To do so, the nonlinear weighted least square error algorithm is employed. Additionally, the proposed method is extended to set forth the parameter estimation of three-phase model of a transmission line needed for unbalanced system studies. Unlike the existing methods, which necessitate PMU installation at both sides of the lines, the proposed method works with few PMUs and has admirable practical merits in nowadays power systems. Case studies through software and hardware simulation efforts demonstrate validity of the modeling approach.

Instability prediction of the inter-connected power grids based on rotor angle measurement

The online detection and prediction of the unstable conditions for interconnect power grids are important tasks to avoid blackout. The increasing installation of phasor measurement units (PMUs) in power systems and the development of the wide-area measurement systems (WAMS) make it possible to analyze the system dynamics using a large amount of real-time synchronous data. This paper proposes a rotor angle measurement based application for online out-of-step monitoring and predicting of the interconnected power systems. An improved Prony analysis method is presented to determine whether and when a power oscillation will lead to power system instability. The accuracy and reliability of the model free dynamic prediction are obtained by adopting an energy-like weight coefficient approximation of the decomposed signals. The self-adaptive resampling of the data and the changeable time-window are designed to make the method suitable for both transient instability and oscillation instability conditions. The effectiveness of the proposed scheme is verified on three test power systems.

Derivation and evaluation of generic measurement-based dynamic load models

Online recorded responses can be used for aggregate dynamic load modelling, taking advantage of the advent of smart grids and the growing installation of phasor measurement units. Although several measurement-based dynamic load models have been proposed in the literature, still most network utilities and system operators take advantage of well-known formulations such as the polynomial and the exponential recovery models. However, these types of load models are only valid for a specific range of operating conditions, thus minimizing their applicability and efficiency. This is mainly due to the fact that the model parameter estimation procedure relies on iterative processes. To this extent, the specific scope of this paper is to present a comprehensive identification procedure for evaluating load models under different loading conditions and further to propose two generic modelling approaches that can be used to derive robust load models that are suitable for dynamic simulations over a wide range. Towards achieving the scope of this paper, Monte Carlo simulations are used to train and validate the data of the loading conditions. Finally, several simulations are performed within the DIgSILENT PowerFactory software to assess the accuracy of the proposed models.

Fault Location Observability using Phasor Measurements Units via Semidefinite Programming

This paper presents a placement algorithm for fault location observability using phasor measurement units (PMUs) in the presence or absence of zero injection buses. The problem is formulated as a binary semidefinite programming (BSDP) model with binary decision variables, minimizing a linear objective function subject to linear matrix inequality (LMI) observability constraints. The model is extended to take into account the unavailability or limited capacity of communication links at some PMU installation buses. The BSDP problem is solved using an outer approximation scheme based on binary integer linear programming. The method is illustrated with a 6-bus test system. Numerical simulations are conducted on the IEEE 14-, 30-, and 57-bus standard test systems to verify the effectiveness of the proposed method.

Optimal placement of phasor measurement units to obtain network observability using a hybrid PSO–GSA algorithm

The rapid growth and expansion of power grids makes analysis and control of such systems a complicated task. Control, management and stability analysis of a power network needs sufficient knowledge of its current state. The traditional measurement system gives little consideration onto the required costs and is no longer a possibility. Phasor measurement units (PMUs) can effectively construct an optimal measurement system to obtain network observability. These units can potentially detect any fault in normal or contingency conditions. Optimal placement of PMUs is very important to minimize the number of costly and unnecessary PMU installations at different buses. In this study, we merged the abilities of particle swarm optimization (PSO) in exploitation and gravitational search algorithm (GSA) in exploration to offer a high-speed hybrid PSO–GSA algorithm for optimal placement of PMU units. The effectiveness of the proposed algorithm has been compared to the prevailing techniques.

Extended Kalman Filter-Based Parallel Dynamic State Estimation

There is a growing need for accurate and efficient real-time state estimation with increasing complexity, interconnection, and insertion of new devices in power systems. In this paper, a massively parallel dynamic state estimator is developed on a graphic processing unit (GPU), which is especially designed for processing large data sets. Within the massively parallel framework, a lateral two-level dynamic state estimator is proposed based on the extended Kalman filter method, utilizing both supervisory control and data acquisition, and phasor measurement unit (PMU) measurements. The measurements at the buses without PMU installations are predicted using previous data. The results of the GPU-based dynamic state estimator are compared with a multithread CPU-based code. Moreover, the effects of direct and iterative linear solvers on the state estimation algorithm are investigated. The simulation results show a total speed-up of up to 15 times for a 4992-bus system.

Reliability Evaluation of Phasor Measurement Unit: A System of Systems Approach

The phasor measurement unit has emerged as a complex, real-time measurement and control system necessitated by the modern power system, the most complex machinery. The extensive installation of phasor measurement units in recent times requires secure and reliable operation. The existing reliability models for phasor measurement unit reliability analysis are constrained by assumptions that disregard the inherent complexity, thus calling for the necessity of a system of systems engineering based reliability model for phasor measurement units. Such a system of systems engineering based model paves the way to accommodate different functional and logical relationships in a suitable way. Another major contribution of this article is the use of statistics of extremes to take into account the scarce failure data for phasor measurement units, which are recent in origin. The results reported in this article validate the efficacy of the system of systems engineering based reliability model.

Realistic Approach for Phasor Measurement Unit Placement: Consideration of Practical Hidden Costs

This paper presents a realistic cost-effective model for optimal placement of phasor measurement units (PMUs) for complete observability of a power system considering practical cost implications. The proposed model considers hidden or otherwise unaccounted practical costs involved in PMU installation. Consideration of these hidden but significant and integral part of total PMU installation costs was inspired from practical experience on a real-life project. The proposed model focuses on the minimization of total realistic costs instead of a widely used theoretical concept of a minimal number of PMUs. The proposed model has been applied to IEEE 14-bus, IEEE 24-bus, IEEE 30-bus, New England 39-bus, and large power system of 300 buses and real life Danish grid. A comparison of the presented results with those reported by traditional methods has also been shown to justify the effectiveness of the proposed model with regard to its realistic and practical nature.

Optimal placement of phasor measurement units to attain power system observability utilizing an upgraded binary harmony search algorithm

Phasor measurement units (PMUs), which provide time-synchronized measurements of current and voltage phasors, are considered as an advanced tool for monitoring, protection and management of modern power systems. In this paper, a novel method for optimal placement of PMUs for complete observability of power network is presented. However the installation cost of the PMUs in different places differ with each other, which is related to some factors like as the number of branches connectedto the placed bus, a big quantity of reported methods for optimal PMU placement problem considered an equal cost for PMU installation in different places. An upgraded binary harmony search algorithm is utilized in this paper as an optimization method to attain the minimum number of PMUs and their relevant locations considering the installation costs of the PMUs. The proposed method is applied to IEEE 14-bus, IEEE 30-bus, IEEE 39-bus and IEEE 118-bus standard test systems to obtain the optimal PMU placement. The simulation results confirm that the proposed method is efficient in optimal PMUs placement with minimum cost of configuration.

An optimal PMU placement method for power system observability under various contingencies

Summary In this paper, an efficient and comprehensive formulation for the optimal placement of phasor measurement units (PMUs) is proposed to minimize the number of PMU installation subject to full network observability. Moreover, the formulation is extended for assuring complete observability under single PMU loss or single line outage cases. Since the proposed optimization formulation is regarded to be a multiple-solution one, both the installation cost and measurement redundancy are employed to differentiate the solutions with the same number of PMUs to be installed. In all of the investigations, the effect of zero-injection buses in the power system is considered. The effectiveness of the proposed method is verified via some IEEE standard systems and compared with some newly reported methods. Results show that the proposed method is simple to implement and more accurate compared to other existing methods. Moreover, by considering the presented method, the minimum number of required PMUs is decreased in some cases. Copyright © 2014 John Wiley & Sons, Ltd.

Phasor measurement units for out of step detection

Synchronized phasor measurements have become an important technology with several international manufacturers offering commercial phasor measurement units (PMUs) which meet the prevailing industry standard for synchrophasors. With the occurrence of major blackouts in many power systems around the world, the value of data provided by PMUs has been recognized, and installation of PMUs on power transmission networks of most major power systems has become an important current activity . This paper presents a transmission line protection scheme based on synchronized phasor measurement units to detect (predict) out of step condition using equal-area criterion which is consistent with transient energy function method for single machineinfinite bus system or two machines system. This scheme uses the measured values of voltages and currents, as complex values, at the generator bus and at the infinite bus. These values of voltage and current are measured in time domain and transformed into phasor domain by using Discrete Fourier Transform to calculate the required areas. The proposed scheme can be used for the detection of out of step condition using equal area criterion with different types of faults at different locations and different models of transmission lines.