Synchrophasor measurement method based on quadrature amplitude modulation

There is a growing emphasis on enabling modernization of traditional power systems by integrating new features and smart technologies to facilitate optimization of grid operations. Phasor Measurement Unit (PMU) is the future of electrical grids employing the use of synchronized phasors to provide system engineers with dynamic supervisory control and post fault analytics. Its exceedingly superior reporting rate compared to contemporary monitoring technologies enables better decision making and rapid actuation of protective equipment. This paper discusses the design of a real-time monitoring system that employs the use of a non-DFT based three phase PMU in accordance with the measurement requirements set in IEEE Standard C37.118.1. The reference for time stamping is Global Positioning System's 1 pulse per second signal. The processors used are Raspberry Pi 3 for the development of PMU and Windows Core 2 Duo computer for the development of PDC. Numerical computing platform, MATLAB is used for plotting of real time data. The paper also discusses previous models of PMU made by the undergraduate students of Electrical Engineering.

Power system networks are rapidly and continuously changing, hence management and control system requires more accurate and reliable information on operating status of the grid for management. This information can be acquired in many ways and can consist of different types of data. Phasor Measurement Units (PMUs) are becoming prominent devices for electrical power system network. They are capable of measuring current and voltage amplitude, Frequency and Rate of Change of Frequency (ROCOF) in synchronized way. Various compliance classes and performance matrices for PMUs are prescribed as per the IEEE standard C37.118.1 for power system synchrophasor. This paper reviews the role of PMUs and compares DFT and space vector methods for synchrophasor estimation.

Synchrophasor technology is an emerging and developing technology for monitoring and control of wide area measurement systems (WAMS). In an elementary WAMS, two identical phasors measured at two different locations have difference in the phase angles measured since their reference waveforms are not synchronized with each other. Phasor measurement units (PMUs) measure input phasors with respect to a common reference wave based on the atomic clock pulses received from global positioning system (GPS) satellites, eliminating variation in the measured phase angles due to distant locations of the measurement nodes. This has found tremendous applications in quick fault detection, fault location analysis, accurate current, voltage, frequency and phase angle measurements in WAMS. Commercially available PMU models are often proven to be expensive for research and development as well as for grid integration projects. This research article proposes an economic PMU model optimized for accurate steady-state performance based on recursive discrete Fourier transform (DFT) and provides results and detailed analysis of the proposed PMU model as per the steady state compliance specifications of IEEE standard C37.118.1. Results accurate up to 13 digits after decimal point are obtained through the developed PMU model for both nominal and off-nominal frequency inputs in steady state.

Phasor Measurement Units (PMUs) are the most modern measurement devices for electric power networks. Their performance, in terms of synchrophasor, frequency and rate of change of frequency (ROCOF) measurement accuracy are crucial for the overall performance of the network management and control applications that are expected to rely on PMU-based distributed measurement systems. In this regard, PMU performance should be assessed under different conditions. IEEE standard C37.118.1, which is particularly focused on PMUs for power transmission systems, reports tests and requirements for PMU compliance. However, some important operating conditions are neglected. In particular, the presence of unbalance in the three-phase system appears relevant for an advisable application of PMUs to distribution networks. In this paper, the impact of unbalance on two important classes of PMU algorithms is discussed. Analytical formulas are derived to estimate the effect of unbalance on synchrophasor, frequency and ROCOF estimations, and they are verified by means of numerical simulations.

The electrical power system is becoming more and more complex with the increasing demand of the electricity across the world, as the world is becoming the global village. The electrical power system must be reliable and safe enough to fulfil the energy requirements with the continuous supply of energy. The chances of power system's blackouts and outages are increasing with its increased complexity. So, there is a need of an efficient control system to make the power system more safe, efficient and reliable. Wide Area Monitoring, Protection and Control system (WAMPAC) is becoming an emerging technology for an efficient monitoring, protection and control of power system. Phasor measurement unit (PMU) is an integrated part of wide area monitoring, protection and control (WAMPAC) system, which can be used for monitoring, protection and control of complex electrical power systems. PMU gives the synchronized phasor measurements of voltage and current and can easily monitor and control even small disturbances in power system to protect the power system from any blackouts and outages before any fault occurs. In the proposed paper a PMU model is designed in MATLAB/Simulink and then PMU is used for power system protection and the comparative analysis are done with the conventional protection technique for an interconnected two-area network power system.

Common phasor measurement units (PMUs) comply with IEEE Standard C37.118 and are capable of managing the test cases formulated inside. These mainly describe electro-mechanic processes (besides step tests). However, electromagnetic processes are not considered, but filtered out. Using subspace-based estimation algorithms provides knowledge of electro-magnetic components within the measurement signal. In addition, the system frequency can be isolated easily. The challenge of (sliding-) window-based algorithms - subspace-based as well as DFT-based methods - is a) finding a trade-off between accuracy and delay (i.e. window length) and b) the inherent assumption of (quasi-) stationarity. In this paper, the concepts of segmentation and back projection are presented which counter these challenges under the assumption of time-critical, time-stamped measurements but not time-critical delivery.

The characteristics of oscillation modes, such as interarea, regional, and subsynchronous modes, can vary during a power system fault, which can cause switching and control actions in the power system. Transient data of the modal response due to such a fault can be acquired through phasor measurement units (PMUs). When the transient data have a long duration, it is desirable to perform modal identification separately on each segment of the transient data, so as to reflect the varying characteristics of oscillation modes. A conventional discrete Fourier transform (DFT)-based method for parametric modal identification cannot be efficiently applied to such a segment dataset. In this paper, a DFT-based method with an exponential window function is proposed to identify oscillation modes from each segment of transient data in PMUs. This window function allows the application of the least squares method (LSM) for modal identification in the same manner as the conventional method. The accuracy of identification of the proposed method is compared with those of the conventional method and a Prony method through synthetic data of transient responses. Its feasibility is also verified by identifying real-world oscillation modes from transient data in PMUs.

This article focuses on addressing the data aggregation faults caused by the Phasor Measuring Unit (PMU) by installing Wireless Sensor Networks (WSN) in the grid. All data that is monitored by PMU should be sent to the base station for further action. But the data that is sent from PMU does not reach the main server properly in many situations. To avoid this situation, a sensor-based technology has been introduced in the proposed method for sensing the values that are monitored by PMU. Also, the basic parameters that are necessary for determining optimal solutions like energy consumption, distance and cost have been calculated for wireless sensors, whereas, for PMU optimal placements with cost analysis have been restrained. For analyzing and improving the accuracy of the proposed method, an effective Binary Logistic Regression (BLR) algorithm has been integrated with an objective function. The sensor will report all measured PMU values to an Online Monitoring System (OMS). To examine the effectiveness of the proposed method, the examined values are visualized in MATLAB and results prove that the proposed method using BLR is more effective than existing methods in terms of all parametric values and the much improved results have been obtained at a rate of 81.2%.

Phasor Measurement Units (PMUs) are nowadays used to monitor and measure the bus voltages and the line currents emanating from the buses. For monitoring all the buses in the power system, optimal placement of PMUs for total power system observability is required. Further, measurement redundancy is also vital to enhance the reliability of state estimation. This paper proposes a new optimization formulation to improve the measurement redundancy with minimum number of PMUs while maintaining full system observability. The problem has been formulated as an integer linear programming problem and solved using CPLEX solver of GAMS software package. The proposed method is tested on IEEE 14 bus and IEEE 30 bus system. The results obtained using the proposed formulation are compared with those obtained using the cost minimization and it has been found that the proposed method is able to increase the measurement redundancy with the same number of PMUs obtained using the cost minimization.

Post-mortem studies carried out after recent power system blackouts have shown that time-stamped measurements from Phasor Measurement Units (PMUs) would have helped to avert these blackouts if they were available. Consequently, there is the need to optimally locate these PMUs to provide information about the system’s state. This paper proposes a novel method incorporating modal participation factors computed from the eigenvalues and eigenvectors of the reduced Jacobian matrix obtained from the system’s power flow with Binary Integer Programming (BIP), in solving the Optimal PMU Placement (OPP) problem while considering the system’s voltage stability. The proposed method identifies the critical buses prone to voltage instability, determines the minimum number of PMUs required for complete topological observability, and the best locations to site the PMUs. The proposed method was tested on benchmark IEEE 14-bus, 30-bus, and 57-bus test networks. Analyses of the results show that the proposed method provides a better procedure for the strategic placement of PMUs in practical networks for voltage stability monitoring especially for the cases of phased (multi-stage) PMU placement limited by the availability of funds and communication channels. Thereby making it necessary to give priority to critical/voltage weak buses during the phased installation process.

As Electrical power system is moving very rapidly toward greener and more sustainable through the usage of Distributed Energy Resources (DERs), complexity and dynamic nature of power system is increasing at a same pace also, Thus to avoid any instability or faults that might occur, quick and real time monitoring of electrical power system is the need of the day. This can be achieved by the usage of Phasor Measurement Units (PMUs). PMU is a time-synchronized metering device that gives very fast and precise data of current and voltage phasors. However, due to their high infrastructure costs of placing, adequate planning for PMU placement is crucial so that the whole system can be observable and the cost of installation of PMUs can be reduced also. In this paper we present optimal PMU placement through Binary Integer Linear Programming (BILP). The simulations are carried out for normal conditions as well as N-1 contingencies. Furthermore, to solve Multiphase PMUs placement problem Multi Criteria Decision Making (MCDM) has been employed. The presented technique is applied on Pakistani Transmission Network as well as on IEEE 14 bus system. The results show that with less number of PMUs better observability of critical buses and lines can be achieved in Pakistani Transmission system as well as in IEEE test systems.

Efficient detection of fault and location can increase the safety and Efficiency of electrical power systems. The fault in power systems can create other faults and outages in the network. Fault analysis includes fault detection, location, isolation of the faulted section from the network, and energy restoration as soon as possible. In this study, an innovative multi-agent system approach proposed for fault location in the electrical network. The smart agents collect the power data (Voltage and current at each point) between different power components (sources, bus, relays, loads) for fault location and efficiently control of circuit breakers operations to restore service in the power systems. The simulation results show the performance of the proposed techniques for fault location in the power system.KeywordsFault locationSmart gridsMulti-agent systems (MAS)Phasor measurement units (PMU)

The continuous development of electric power systems characterized by an increasing potential of decentralized energy generation requires high precision measurement technologies for an effective and reliable network monitoring and system state assessment to ensure the high level of present and future security of energy supply. One possibility to capture system parameters, which has been established primarily within transmission networks, is the use of Phasor Measurement Units (PMU). Taking Smart Grid discussions into account, PMU usage in distribution systems, under particular conditions regarding observability aspects should also be considered [2]. The goal of this paper is to introduce the new requirements for PMU measurement accuracy testing according to IEEE standard C37.118.1 [1]. This publication focuses on two things: the development of automated procedures for a certified PMU test bench, and a way to extend an existing test concept according to the new testing regulations. Based on these investigations, exemplary and representative measurements, which were made with this automated test bench are presented and analyzed for one proposed static test scenario.

New data acquisition technologies, such as phasor measurement units (PMU), have been implemented in recent years to operate the power system with more reliability and control by improving the protection schemes like line differential protection or damping the inter-area oscillations. The present standard IEEE C37.118 only provides general information about the testing conditions and requirements, without giving any specifics.. To create the PMU data function for the applications and thereby make the power system more reliable, the appropriate PMU test standards have to be developed and disseminated. Future testing methods should ensure that units from different manufacturers are tested identically and function properly under different repeatable test scenarios and test stand set up conditions. This paper presents experiences from tests of PMU accuracy and calibration conducted in Europe and the USA, which will facilitate the development of future standards. The test stand itself and the test results from the various PMU manufactures are presented, compared and discussed in this paper, taking into account the standardization issues.

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.