Recent Development in Power System Dynamic State Estimation (original) (raw)
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Effect of synchronized Phasor Measurement Units Locations on power system state estimation
2008 International Conference on Computer Engineering & Systems, 2008
The phasors readings of the Phasor Measurement Units (PMUs) are taken into consideration in state estimation analysis. The paper presents the effect of changing the locations and numbers of PMUs through the buses of the power network on the system state estimation results. A computer program is built and tested on 14-bus IEEE standard system. Also it is applied on a system depicted from the Egyptian electrical power network. The simulation results are discussed in details.
The traditional methods of security assessment using offline data and SCADA data have become inconsistent for real time operations. The latest and propelled strategy in electric power system used for security assessment is “synchrophasor†measurement technique. The device called Phasor measurement unit (PMU) provides the time stamped data for proper monitoring, control and protection of the power system. PMU measures positive sequence voltage and current time synchronized to within a microsecond. The time synchronization of data is done with the help of timing signals from Global Positioning System (GPS). However, Phasor measurements units cannot be placed on every bus in a network mainly because of economical constraints. In this paper we provide a literature survey of determining the minimum number of Phasor measurement units to be placed in a given network so that the system becomes observable.
Application of Synchronized Phasor Measurements Units in Power Systems
The last decades, electric power industry is undergoing multiple changes due to the process of deregulation, providing efficient power generation, technological innovations, and eventually lower retail prices. In this environment, dynamic phenomena in power systems have made ever more urgent the development of reliable tools for their monitoring and control. An effective tool for the close monitoring of their operation conditions is the state estimator. The traditional estimators are based on real time measurements obtained through SCADA (Supervisory Control and Data Acquisition) system. These measurements are commonly provided by the remote terminal units (RTUs) installed at the high voltage substations. The phase angle of bus voltages can not be easily measured due to technical difficulties associated with the synchronization of measurements at RTUs. Global Positioning System (GPS) alleviated these difficulties and led to the development of Phasor Measurement Units (PMUs). This weakness was eliminated with the arrival of GPS, which led to the development of Phasor Measurement Units. A PMU unit, equipped with a GPS receiver, provides high accuracy voltage and current phasor measurements with respect to a common reference phase angle. In the first part of the paper, an overview of the PMU technology and a review about the optimal allocation of PMUs in power network are presented. The most important issues regarding design and operation of PMUs are discussed and an analysis of their commercial penetration in the electric energy markets is made. The second part of the paper presents a wide range of applications related with the choice of the strategic PMU placement as well as an algorithm for finding the optimal number of PMUs needed for full observability.
On the use of PMUs in power system state estimation
2011
Synchronized phasor measurement units (PMUs) are becoming a reality in more and more power sys- tems, mainly at the transmission level. This paper presents, in a tutorial manner, the benefits that existing and future State Estimators (SE) can achieve by incorporating these de- vices in the monitoring process. After a review of the rele- vant PMU technological aspects and the associated deploy- ment issues (observability, optimal location, etc.), the alter- native SE formulations in the presence of PMUs are revis- ited. Then, several application environments are separately addressed, regarding the enhancements potentially brought about by the use of PMUs.
Phasor Measurement Units (PMUs) Allocation for Power Systems State Estimation
2012
The recent development of phasor measurement units (PMUs), enhancing synchronization and high time-resolution of measurements, allows the creation of dynamic snapshots and makes network real-time observability possible. A proposed analysis of power system observability and the rules of PMUs placement with the aim of linear static state estimation (SE) of power system networks are presented in this paper. According to the Power System Analysis Toolbox (PSAT), MATLAB toolbox, several algorithms of PMUs allocations as well as their differences and relations are introduced such as a graph-theoretic procedure based on Depth First Search, Simulated Annealing Method, Minimum Spanning Tree Method, and others. These different methods are used to benchmark the real networks with different scales, topologies and voltage levels in Egypt besides the standard test systems of IEEE 14-bus and IEEE 30-bus. The obtained results indicate the effectiveness of the applied methods of optimal PMUs placement for power system observability with the aim of linear static SE as well as the further requirements for optimal PMUs placement, which are not provided by any of the different methods for future work. By comparing the studied methods, we found that, it could not be said that there is an algorithm is optimal for all cases.
Power System Dynamic State Estimation With Synchronized Phasor Measurements
IEEE Transactions on Instrumentation and Measurement, 2000
The dynamic state estimation (DSE) applied to power systems with synchrophasor measurements would estimate the system's true state based on measurements and predictions. In this application, as phasor measurement units (PMUs) are not deployed at all power system buses, state predictions would enhance the redundancy of DSE input data. The significance of predicted and measured data in DSE is affected by their confidence levels, which are inversely proportional to the corresponding variances. In practice, power system states may undergo drastic changes during hourly load fluctuations, component outages, or network switchings. In such conditions, the inclusion of predicted values could degrade the power system state estimation. This paper presents a mixed-integer programming formulation of DSE that is capable of simultaneously discarding predicted values whenever sudden changes in the system state are detected. This feature enhances the DSE computation and will not require iterative executions. The proposed model accommodates systemwide synchronized measurements of PMUs, which could be of interest to smart grid applications in energy management systems. The voltage phasors at buses without PMUs are calculated via voltage and current measurements of adjacent buses, which are referred to as indirect measurements. The guide to the expression of uncertainty in measurement is used for computing the confidence level of indirect measurements based on uncertainties associated with PMU measurements as well as with transmission line parameters. Simulation studies are conducted on an illustrative three-bus example and the IEEE 57-bus power system, and the performance of the proposed model is thoroughly discussed.
Optimal Placement of PMU for Power SystemObservability
International Journal of Advanced Research in Electrical, Electronics and Instrumentation Energy, 2014
Phasor Measurement Unit (PMU) is a relatively new technology that, when employed in power networks, offers real-time synchronised measurements of the voltages at buses and currents along the lines that connect them. This is accomplished by using a GPS based monitoring system which facilitates time synchronisation of measurements and unlike SCADA, makes the measured data available in Real-Time format. SCADA is not able to provide Real-time data due to the low speeds at which RTUs (Remote Terminal Units) provide data. Availability of time-stamped phasor measurements makes PMUs preferable for power system monitoring and control applications such as State Estimation, Instability Prediction Analysis, Real time monitoring of the system conditions, Islanding Detection, System Restoration and Bad Data Detection. Since PMUs are expensive, their procurement and installation needs to be planned both in terms of economy and utility. Usually utilities like to see that the power network becomes f...
Energies
Present-day power systems are mostly equipped with conventional meters and intended for the installation of highly accurate phasor measurement units (PMUs) to ensure better protection, monitoring and control of the network. PMU is a deliberate choice due to its unique capacity in providing accurate phasor readings of bus voltages and currents. However, due to the high expense and a requirement for communication facilities, the installation of a limited number of PMUs in a network is common practice. This paper presents an optimal approach to selecting the locations of PMUs to be installed with the objective of ensuring maximum accuracy of the state estimation (SE). The optimization technique ensures that the critical locations of the system will be covered by PMU meters which lower the negative impact of bad data on state-estimation performance. One of the well-known intelligent optimization techniques, the genetic algorithm (GA), is used to search for the optimal set of PMUs. The proposed technique is compared with a heuristic approach of PMU placement. The weighted least square (WLS), with a modified Jacobian to deal with the phasor quantities, is used to compute the estimation accuracy. IEEE 30-bus and 118-bus systems are used to demonstrate the suggested technique.
Reviewing issue of Phasor Measurement Units Optimization for Power System Observability
— The electric power grid is a complex interconnected system that may be subjected to blackouts and faults. It is necessary for utilities to repair and restore their power system as quickly as possible during extreme conditions. The exact state of the electric grid is needed to perform any corrective or preventive actions during such conditions. To overcome this problem we find a method to find minimum number of phasor measurement units (PMUs) for complete observability of power system network for normal operating conditions. Phasor measurement unit (PMU), which is based on the global positioning system (GPS) technique, is able to provide power engineers with immediate and precise measurements.