Phasor Measurement Units Channel Research Articles

Transmission line parameters estimation in the presence of realistic PMU measurement error models

Proposals have been presented in literature to estimate line parameters and monitor their changes. Synchrophasor measurements from phasor measurement units (PMUs) have appeared as a possible breakthrough for accurate estimation. However, few methods consider a realistic measurement chain including PMUs and instrument transformers and their systematic and random error contributions. This paper proposes an improved method to simultaneously estimate line parameters and systematic measurement errors on multiple network lines. The algorithm is designed to deal with realistic PMU measurement errors and, in particular, with phase-angle errors caused by common time-base errors on multiple PMU channels. The impact of PMU measurement errors is investigated to achieve a comprehensive view of the performance under realistic conditions. The results obtained on an IEEE test network prove the advantages of the proposed method with respect to other recent methods and its robustness in the presence of mismatches in the error model.

An Optimal Scheme for Installation of PMUs and IEDs to Reinforce Electricity Market Immunity Against Data Attacks in Smart Grid

An intruder can disrupt the electricity market operation by injecting malicious data into the sensor measurements to induce profit/loss to a utility/consumer. Robustness in the electricity market operation against false data injection attacks (FDIAs) can be achieved by optimal deployment of phasor measurement units (PMUs) and intelligent electronic devices (IEDs). The nonlinear relationship between sensor measurements, state variables, and nodal electricity price, along with the financial constraints associated with deploying high-cost measurement devices, increases the complexity of solving the FDIA resilient sensor placement task. The solution demands a tradeoff between the financial implications of installing PMUs/IEDs and the nodal price deviation during FDIA. To overcome the above challenges, the task of identifying strategic sensor locations has been formulated as a binary optimization problem. The solution of the problem derived using binary Harris hawks optimization identifies the most vulnerable bus/branch measurements with regard to nodal price deviation due to FDIA. To generalize the applicability of the proposed scheme, the formulation has been carried out while considering the realistic constraints related to PMU channel limitations and the location of the zero injection bus. The effectiveness of the proposed work has been validated for benchmark test systems against different degrees of FDIAs.

Novel Optimal PMU Placement Approach Based on the Network Parameters for Enhanced System Observability and Wide Area Damping Control Capability

The placement of phasor measurement units (PMUs) in modern power systems provides improved monitoring and control characteristics of the entire electrical network. Nevertheless, the installation of additional PMU devices is associated with relatively high cost and complicated communication infrastructure. As a result, the allocation of the PMU devices needs to be optimized to achieve complete observability of the system while minimizing the related cost. This paper proposes a new method for solving the optimal PMU placement (OPP) problem using integer linear programming (ILP) such that the global optimal solution is guaranteed. As opposed to the reported studies in the literature, the proposed method considers the network parameters such as the series impedances and the shunt admittances of the transmission lines and transformers impedances in the formulation of the OPP problem. These parameters are found to have a crucial impact on the observability of the entire network. A distinguishing feature of the proposed approach is that it decomposes the network into smaller subnetworks, with reduced dependence between them, thus making it scalable when applied to typical networks. In addition, the proposed method seeks to achieve the maximum measurement redundancy while considering the impact of failures among individual PMU devices (N-1 contingency), the PMU channel limitation and the pre-existing conventional measurements. Furthermore, the presented approach incorporates additional constraints which are associated with the control feedback signals of the supplementary damping controllers and thus enhance the small signal stability of the power grid. The effectiveness of the proposed method is tested using different standard IEEE systems as well as a large practical network.

Tri-Objective Optimal PMU Placement Including Accurate State Estimation: The Case of Distribution Systems

This paper presents a tri-objective Optimal Phasor Measurement Units (PMUs) Placement (OPP) strategy that is focused on the minimization of i) the total number of PMU channels, ii) the maximum state estimation uncertainty based only on high-rate PMU data and iii) the sensitivity of state estimation to line parameter tolerances. The proposed formulation keeps into account system observability with and without contingencies due to single-line and PMU faults. Also, it includes the effect of possible zero-injection buses and a-priori constraints on both the number of PMU channels and the type of PMU measurements performed at each bus. Due to the nonlinear combinatorial nature of the proposed OPP problem, this is solved through a custom implementation of the nondominated sorting genetic algorithm II (NSGA-II). The analysis of the proposed OPP strategy is focused on distribution systems. The placement results obtained using four test systems of different size show that increasing the number of buses instrumented with PMUs and/or the number of PMU channels beyond given thresholds just leads to larger costs with negligible further reductions in both state estimation uncertainty and sensitivity to line parameters tolerances. Moreover, if PMUs with just two three-phase channels are used, we can avoid instrumenting between 30% and 40% of buses with a minor impact on state estimation performance even in the case of contingencies. This percentage can be slightly increased if multi-channel PMUs are used. However, this choice generally is not profitable.

Optimal PMU arrangement considering limited channel capacity and transformer tap settings

The transition from the conventional power systems to smart grids has led to the modernisation of the measuring infrastructure used for their monitoring and control. Among the devices used to accomplish these tasks, phasor measurement units (PMUs) play a key role since they can provide extremely accurate synchronised voltage and current phasor measurements. The optimal PMU placement (OPP) problem, which focuses on minimising the number of PMUs for full system observability, has long been a popular research topic. The vast majority of the available OPP techniques have treated each transformer tap setting (voltage turns ratio and phase-shifting angle) as a fixed network parameter. Such an assumption can lead to misdirecting residuals in adjacent valid measurements when the modelled tap setting is incorrect. The aim of this study is to propose a substation-oriented OPP method based on a binary semidefinite programming algorithm, considering the observability of the transformer tap settings and the limited PMU channel capacity. The method is illustrated using an 8-bus test system. Numerical results using different size IEEE systems are presented and discussed. The proposed approach is further applied to the Polish 3120-bus system to show its efficacy in solving the OPP problem for large-scale power systems.

Optimal co‐placement method considering non‐homogeneous PMU channel capacities

In this study, a topology defragmentation method is developed for co-placements of phasor measurement units (PMUs) and their communication infrastructure. Electric power networks are defragmented into sets of branches and a realistic cost model, based on reports from industry, is developed. Instead of considering channel limitations, more practical consideration of the presence of dual-use line relays and PMUs with different channel capacities is used to obtain a least-cost solution for specified levels of observability. Formulations are proposed to address budget limitations, to maximise benefits from add-on application, and to enhance application-sensitive deployments. The approach is demonstrated on a number of IEEE test networks and results reflect practical situations where optimal solutions (especially PMU buses and the capacity of deployed PMUs) depend on the availability of equipment, existing devices, and the level of observability specified. Solutions obtained to specify the bus, branch, PMU type, and phasor data concentrator to connect to and are optimal without the need for algorithmic parameter tuning. It is established, among other conclusions, that placement results should transcend beyond mere statements of the number of installations, but on the specifics of the deployments at the buses, branches, and storage locations.

A New Approach to Reliability Assessment and Improvement of Synchrophasor Communications in Smart Grids

Wireless communications can facilitate transfer of synchrophasor data between spatially separated phasor measurement units (PMUs) and phasor data concentrators (PDCs). However, such communication systems may impose random access delay and failure on PMU channels that lead to missing synchrophasor data frames at the output of the PDC. This paper presents a new approach for online reliability assessment and improvement of synchrophasor data communications. The proposed approach involves elaborate estimation and probabilistic prediction algorithms that trigger a prioritized handover mechanism in order to minimize the number of synchrophasor data frames that are missing over successive time stamps. Extensive simulations based on the LTE communications in a low-voltage distribution feeder confirm significant performance improvement and fast fault detection under the communication link failures. This non-intrusive approach can be adopted by network operators to ensure reliable transmission of synchrophasor data to monitoring, control, and protection applications in smart grids.

An investigation of the impact of synchrophasors measurement on multi-area state estimation in active distribution grids

ABSTRACT This paper examines the impact of synchrophasors measurement from a number of phasor measurement units (PMUs) on multi-area state estimator (MASE) in the distribution grid (DG). The benefits are largely in the form of improved state estimation (SE) accuracy. An important decision in the implementation of PMU-based SE is the optimal selection of the channel capacity of the PMUs. This decision becomes more important for the distribution systems because of larger number of measurement points as compared to the transmission system and also because of higher cost of PMUs with more measurement channels. Further, critical measurement analysis is important as they indicate the robustness of measurement system. In this paper to compare the robustness of the measurement system and the accuracy of SE, various performance metrics were compared for conventional, infinite channel and PMUs with limited number of channels. Therefore, an important contribution of the present work is the impact analysis of different number of PMU channels on the accuracy of the results of MASE and also on the measurement robustness for distribution networks. The results presented are expected to be useful for the utilities when designing a PMU-based MASE for the distribution grids.

A Novel Multiobjective OPP for Power System Small Signal Stability Assessment Considering WAMS Uncertainties

In this paper, a multiobjective optimization method for the placement of phasor measurement units (PMUs) is proposed. The proposed method simultaneously considers different objectives including the power system small signal stability, the probability of system observability, and the total cost of PMUs. In the proposed optimal PMUs placement (OPP) model, wide area measurement system (WAMS) uncertainties and network configuration changes are also considered, while the variable cost of PMUs, based on the number of PMU channels is also observed. The elitist nondominated sorting genetic algorithm (NSGA-II) is used to obtain the Pareto optimal solutions and the best compromise final solution is selected by the decision maker on the basis of his priorities. Some simulation results on different test systems in different scenarios are presented and discussed. They confirmed that the proposed multiobjective model provides effective information for small signal stability assessment with minimum PMU cost in the presence of uncertainties.

Novel notions of zero injection property of buses in optimal PMU location with efficient observability enhancement focusing on security concepts

In this paper, a new method is proposed for security-oriented, optimal placement of phasor measurement units (PMUs) incorporating efficient observability redundancy. In this way, novel concepts in zero-injection buses (ZIBs) are introduced. The proposed concepts regard aspects of the ZIBs effect that have not yet been studied; thus, by applying this concept, maximum possible capacity of the ZIBs will be available for use. Therefore, the proposed method is capable of producing optimum possible results with tangibly higher ZIBs capacity usage and measurement redundancy levels than those reached in preceding works. In addition, the reliability of fragile areas monitoring from overvoltage viewpoint is enhanced. Considering the fact that complete synchronized network observability is undeniably significant for making control decision in critical conditions to avoid brownouts or blackouts, a novel practical framework is proposed based on backup observability concept in order to model branch outage in addition to PMU loss and channel failure. All proposed security models can be tested by practical, large-scale test systems such as Polish 2383- and 3375-bus. Also, in the case of branch outage, selective security criteria are considered so as to enhance security of network observability against cascading failures in electric power systems.

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.

Enhancing observability in MILP-based optimal joint allocation of PMU channels and conventional measurements with new security concepts

Since buses in power systems have a different number of connected branches, they require Phasor Measurement Units (PMUs) with different number of measuring channels. In this paper, a multi-objective channel-based method is proposed for optimal allocation of PMU base units, PMU measuring channels, and Flow Measurements (FMs) for power system observability. The main objective function encompasses cost of PMU base units and their measuring channels as well as FMs. Unlike previous methods, PMU channels are modeled as binary optimization variables, the optimal assignment of which is decided by the optimization problem. Under this framework, a PMU assigns measuring channels to observe its adjacent buses only if they are economically justified. The second objective function maximizes measurement redundancy at selected buses in a more controlled way. For a more economical solution, existing FMs are employed as network resources along with placing new PMUs and FMs. Moreover, PMU failures and branch outages are modeled using a novel approach that is more cost-effective than existing methods. Furthermore, channel failure is also introduced and modeled as a new type of contingency. Results obtained from the proposed method clarify its efficiency from economic perspective.

Integrated Mutation Strategy With Modified Binary PSO Algorithm for Optimal PMUs Placement

Optimal phasor measurement units (PMUs) placement refers to the strategic placement of PMUs to achieve the full observability of power systems with a minimum number of PMUs. A strategic placement is needed because of the economic or technical restriction that hinders the deployment of PMUs on every bus. A modified version of the binary particle swarm optimization method is proposed in this paper by integrating a mutation strategy and the V-shaped sigmoid function for placing the PMUs that maintains the full power system observability in the presence of zero-injection bus, single PMU loss, and PMU's channel limits while maximizing the measurement redundancy. The solution that has the highest measurement redundancy was selected as the best placement of PMUs. The use of mutation strategy and V-shaped sigmoid function in this paper improves the population diversity, thereby minimizing the chance of the particles being trapped in the local optima, consequently leading to a quality solution. In order to validate its effectiveness, the results obtained by the proposed method are compared with other published techniques to demonstrate the accuracy and validity of the proposed technique. The results of the IEEE 300-bus system show that the proposed method effectively managed to reduce the number of PMUs needed.

Optimal PMU Placement Using Modified Greedy Algorithm

Phasor measurement units (PMUs) provide synchronized measurements of real-time phasors of voltages and currents. It is considered as an important element of the smart wide area measurement system used in advanced power system monitoring, protection, and control applications. This paper proposes a new approach based on a greedy algorithm to solve the optimal phasor measurement unit placement (OPP) problem in the power network. The main purpose of proposed approach is to find out a high-quality solution in a reasonable time that ensures the practicability when applying for a real power network. The OPP problem is solved under both normal operating and contingency conditions. Moreover, some other realistic aspects that may affect the OPP problem, such as PMU channel limitation, zero injection bus, the presence of conventional measurements, are also considered to solve simultaneously. The simulations on IEEE 14-bus, 30-bus, 57-bus, 118-bus test systems, and especially on a large-scale network—the Polish 2383-bus system, are presented for evaluating the feasibility of proposed approach. The results of this study showed that the proposed method is effective and feasible to solve the OPP problem for a real power network.

Optimal PMU Placement for Numerical Observability Considering Fixed Channel Capacity—A Semidefinite Programming Approach

This letter presents a 0-1 semidefinite programming (SDP) approach to solve the problem of optimal placement of phasor measurement units (PMUs), considering the existence of conventional measurements and zero injections as well as the impact of PMU channel limits. The proposed formulation can prevent the wasteful utilization of different PMUs observing incident branch current phasors at a given bus more than once. The method is tested on the IEEE 57-bus test system.

Pragmatic multi-stage simulated annealing for optimal placement of synchrophasor measurement units in smart power grids

Conventional power grids across the globe are reforming to smart power grids with cutting edge technologies in real time monitoring and control methods. Advanced real time monitoring is facilitated by incorporating synchrophasor measurement units such as phasor measurement units (PMUs) to the power grid monitoring system. Several physical and economic constraints limit the deployment of PMUs in smart power grids. This paper proposes a pragmatic multi-stage simulated annealing (PMSSA) methodology for finding the optimal locations in the smart power grid for installing PMUs in conjunction with existing conventional measurement units (CMUs) to achieve a complete observability of the grid. The proposed PMSSA is much faster than the conventional simulated annealing (SA) approach as it utilizes controlled uphill and downhill movements during various stages of optimization. Moreover, the method of integrating practical phasor measurement unit (PMU) placement conditions like PMU channel limits and redundant placement can be easily handled. The efficacy of the proposed methodology has been validated through simulation studies in IEEE standard bus systems and practical regional Indian power grids.

Ant colony optimizer for phasor measurement units placement

This paper proposes an approach for optimal placement of phasor measurement units (PMUs) for complete observability at normal and emergency conditions such as any single line outage or any single PMU loss using ant colony optimization (ACO) algorithm. The objective function is to find the optimal locations of PMUs and the minimum number of PMU channels by optimizing the logic decision of control variables, under the observability constraint. The ACO algorithm is applied to the standard IEEE 14-bus, 30-bus and New England 39-bus systems. In addition, an application of the proposed algorithm to a real power system of the west Delta network (WDN) as a part of the Unified Egyptian Network (UEN) is presented. The results obtained are compared with those obtained using other techniques. Simulation results show that the proposed ACO algorithm is more accurate and efficient for obtaining the optimal placement of PMUs with minimum number of PMU channels, especially with increasing the system size.

OPTIMAL PLACEMENT OF PHASOR MEASUREMENT UNITS WITH LIMITED CHANNELS USING ANT COLONY OPTIMIZATION ALGORITHM

This paper proposes an approach for optimal placement of phasor measurement units (PMUs) for complete observability at normal and emergency conditions such as any single line outage or any single PMU loss using ant colony optimization (ACO) algorithm. The objective function is to find theoptimallocations of PMUs and the minimum number of PMU channels by optimizing the logic decision of control variables, under the observability constraint. The ACO algorithm is applied to the standard IEEE 14-bus, 30-bus and New England 39-bus systems. Add to that, an application of the proposed algorithm to a real power system of the west Delta network (WDN) as a part of the Unified Egyptian Network (UEN) is presented. The results obtained are compared with those obtained using other techniques. Simulation results show that the proposed ACO algorithm is more accurate and efficient for obtaining the optimal placement of PMUs with minimum number of PMU channels, especially with increasing the system size.

A new method for optimal placement of phasor measurement units to maintain full network observability under various contingencies

The application of phasor measurement units (PMUs) in power systems is increasing because of their advantages such as the capability for online state estimation and improvements in the speed of control, and protection systems. In this paper, we propose a new method using binary integer linear programming for the optimal placement of PMUs to guarantee full observability of a power system as well as maximizing the measurement redundancy. Moreover, the problem of the optimal placement of these units in the case of a single PMU loss or single line outage is investigated. A practical limitation is also considered on the maximum number of PMU channels, in the proposed formulation. In all of the investigations, the effect of zero-injection buses in the power system was considered. The efficiency of the proposed method was demonstrated in different conditions. The method was applied to several IEEE standard test systems, i.e., the 14-, 30-, 39-, 57-, and 118-bus systems, and in two very large-scale systems, i.e., 2383- and 2746-bus systems. The simulation results verified the acceptable performance of the proposed method.