Modular PMU tester

In uses, such as stability surveillance of an electric power system, the synchronous voltage current phasor measurement using GPS satellite base timing keeping technology is demanded. In the past, the synchronous phasor measurement technique of a voltage current based in DFT conversion theory was proposed, and it was established as an IEC standard[1]. In the actual electric power system, the frequency of voltage in each place is delicately different, and it is always changing. Since the sampling data in the time window of fixed width cannot take in the integer cycle of a voltage waveform and does not satisfy the signal periodicity conditions of Fourier transform, a spectrum leakage phenomenon occurs. By this, the accuracy of the synchronous phasor measurement by single DFT-BIN frequency falls. This paper proposes the method of realizing recursively DFT conversion with a window function [RWDFT] which can reduce the influence of system voltage frequency change. Moreover, the method of calculating Phasor of true signal frequency is proposed by compounding three or more DFT conversion factors. In simulation verification, the synchronous phasor measuring method which applied the above two methods has checked that a highly precise Phasor measurement result was obtained in system voltage frequency change.

This paper provides initial justification for adopting a distributed architecture for phasor measurement unit. The characteristics of synchronized phasor measurement is studied in detail. The benefits and short comings of phasor measurements are highlighted from the point of view of their different applications. The need for extension of phasor measurement unit functionality is brought out through analysis of the application and synchronized phasor measurement characteristic compatibility. The concept of phasor measurement unit is extended to a distributed system with several small functions working independently to provide a complete functionality of a phasor measurement unit. The proposed substation automation works on the framework of IEC 61850 process bus.

This paper proposes a redefinition of the power system quantities often said to be described by a synchro-phasor and measured by a phasor measurement unit. Problems with what are often called “synchronous phasor measurements” include the facts that they are not truly synchronous, and the quantity being measured is not truly a phasor. This paper proposes a new method of making measurements that overcomes these problems. It tests the proposed definitions and measurement methods with “synthetic” signals, and shows that the method provides understandable and consistent results.

As the node power is controllable, the traditional dynamic security region (DSR) is defined on power injection space. The phasor measurement unit (PMU) can measure and transfer the state variables (phase angles) of power system synchronously. How to make full use of the synchronized phasor measurement (SPM) in the security monitoring, protection and control of power system is a challenging research task. In this paper, we presented the concept of practical dynamic security region (PDSR) in phase angle space. A study on PDSR of power systems shows that critical points satisfying transient stability in angle space can still be described by one or a few critical hyper- planes. With the PDSR in the node angle space, a concise expression to calculate the transient stability margin of a current operation point in each direction in node angle space is suggested. Besides, this paper suggested an approach to acquire the PDSR in low-dimensional angle space based on dynamic equivalence of transient stability and a method to select appropriate locations for partially equipping PMU, which provide an innovative way of making use of the PMU information to carry out dynamic security monitoring of power systems.

In this paper, the modeling of a Phasor Measurement based Wide Area Monitoring and Control System was developed and presented. The proposed system emphasizes the need for monitoring and control of transmission lines connected to Distributed Energy Resources. In this work, the modeling for a complete scenario of a Discrete Fourier Transform based Synchronized Phasor Measurement Unit is presented. The performance of the developed Phasor Measurement Unit was evaluated by computing Total Vector Error and validated in accordance with IEEE C37.118.1 standard for synchrophasor measurements. The proposed system was simulated using MATLAB/Simulink environment and it is tested under two possible cases; normal operation and fault state. It was verified that the power system status can be easily monitored and controlled in real time by using the measured bus data. This improves the overall system reliability and avoids cascaded blackout during fault occurrence. For smart grid applications the simulation results confirm the validity of the proposed Phasor Measurement based Wide Area Monitoring System.

The Phasor Measurement Unit(PMU) is used for accurate measurement of synchronous phasor of voltages and currents at separated points across the power grid and are widely installed at the transmission level. As the next point of setup in smart grid, PMU is necessary for components control, fault detection and control, energy management in distribution network. This paper first illustrates the architecture of PMU setup that has been fully designed by the authors and then describes the challenge of designing and implementing which integrates field measurements to deliver Global Positioning System (GPS) synchronized phasor data to the distribution networks. By using this platform, our efforts have provided the real-time data detected, power quality analysis and direction to future efforts to analyze data in cloud calculation, harmonic state estimation, etc.

This paper is concerned about optimal placement of synchronized phasor measurements that can monitor voltage and current phasors along network branches. Earlier investigations on placement of phasor measurement units (PMUs) have assumed that a PMU could be placed at a bus and would provide bus voltage phasor as well as current phasors along all branches incident to the bus. This study considers those PMUs which are designed to monitor a single branch by measuring the voltage and current phasors at one end of the monitored branch. It then determines the optimal location of such PMUs in order to make the entire network observable. The paper also addresses the reliability of the resulting measurement design by considering loss or failure of PMUs as well as contingencies involving line or transformer outages. Developed placement strategies are illustrated using IEEE test systems.

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.

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.

There have been quite a few attempts to compute synchronous generator parameters based on voltage and current synchrophasors taken under power system transients. However, we have not seen any publications with thorough analysis as to how soon the phasor measurement unit reacts to disturbance conditions, which components of the transient are filtered out and which are passed through, as well as what the total vector error is. The goal of this research is to determine all of these characteristics of a phasor measurement unit when playing back transient oscillograms for a stator short circuit obtained through mathematical modeling. The transient oscillograms have been derived via both a full Park-Gorev system of flux linkage equations as well as the MATLAB/Simulink Synchronous Machine block. Physical modeling was then conducted via a real-time digital simulator (RTDS) along with a dedicated phasor measurement unit ENIP-2 (PMU), and the stator current phasors were recorded. Our analysis has shown that both RTDS and ENIP-2 (PMU) almost entirely filter out the exponentially decaying DC component of the fault current while closely following the periodical signal envelope. The total vector error has been estimated to become below 1–2 % after around 0,02–0,03 s into the fault when selecting the “P” class filters according to IEEE C37.118. We have come to a conclusion that synchrophasor measurements under power system disturbances could be utilized for estimating the synchronous, transient, and subtransient generator parameters. The selected synchronous machine model in the form of flux linkage equations is correct, as the obtained transient oscillograms are exactly the same as those produced by Simulink. “P” class phasor measurements can be recommended for representing transients in the stator circuit of a synchronous generator. The results of this investigation are meant to be employed for synchronous machine parameter estimation based on phasors sourced from RTDS and, hopefully, from phasor measurement units installed at power plants.

The pursuit of achieving total power network observability in smart grids using Phasor Measurement Units (PMUs) carries a significant promise of real-time Wide-Area Monitoring, Protection, and Control (WAMPAC). PMU applications eliminate periodical measurements, thereby increasing accuracy through a high sampling rate of the measured power systems quantities. The high costs of installation of PMUs for total power system observability presents a challenge in the implementation of PMUs. This is due to the expensive costs of PMU devices. This has led to a prominent optimal PMU placement (OPP) problem that researchers tirelessly aim to solve by ensuring a complete power network observability while using the least installed PMU devices possible. In this paper, a novel Binary Firefly Algorithm (BFA) based on the node degree centrality scores of each bus is proposed to minimize PMU installations. The BFA solves the OPP problem in consideration of the effect of Zero Injection Buses (ZIBs) under normal operation and single PMU outage (SPO). The robustness and efficiency of the proposed algorithm is tested on IEEE-approved test systems and visualized with a force-directed technique on an undirected power network graph. The proposed BFA yields the same but better optimal PMU numbers, obtained by existing meta-heuristic optimization techniques found in the literature for each of the IEEE test cases, as well as highlighting the cost–benefit of having a robust system against single PMU loss while considering the ZIB effect for an improved system measurement availability.

This paper presents a real-time voltage stability assessment in distribution networks (DNs) capable of separating the effects of the transmission and distribution network by using synchronized phasor measurements. The method aims to assist transmission and distribution system operators to quantify the need of their services in different parts of the DN in order to provide adequate voltage support to their specific stakeholders. The method uses data from phasor measurement units (PMUs) to estimate models for both DN and transmission network (TN). A Thevenin equivalent model is estimated for the TN and a T-model for the DN. By applying the superposition theorem on these two models, the contribution of each network to the overall system voltage stability can be distinguished at a specific bus (equipped with a PMU). The method has been validated by a hardware-in-the-loop setup which consists an OPAL-RT real-time simulator and three PMUs.

Operational practices of both power transmission and distribution grids are impacted by the increasing connection of renewable energy resources, electric vehicles and energy storage systems. A timely and accurate knowledge of the system state, coupled with a level of automation able to protect or control the system, enables a better operation of the electrical grids. In this respect, synchrophasor networks, might provide system operators with wide-area, synchronized, low latency, high refresh-rate measurements from phasor measurement units (PMUs). This thesis focuses on the design and validation of resilient synchrophasor networks in order to address some of the challenges that are preventing the adoption in real-fields of what proposed by the literature. First, the architectural layers of synchrophasor networks are described with particular focus on the time dissemination techniques suitable for phasor measurement units. Then, we propose a new data-pushing logic able to minimize the latency introduced at the concentration point without increasing the data incompleteness. The data-pushing logic is validated in three real synchrophasor networks adopting different telecom infrastructures (i.e., 4G-LTE, optical fiber links and twisted pairs). In the context of reliable operation of synchrophasor networks, we propose an algorithm able to deal with intentional or unintentional bad data measurements. We also impersonate an attacker and we show that it is possible to forge delay attacks undetectable by state-of-the-art bad-data detection algorithms that can lead to physical grid damage. We use the proposed bad data algorithm as an effective way of neutralizing these attacks. The IEEE C37.118 Class-P Std compliant synchrophasor extraction algorithm adopted in the real-fields is also implemented and validated in a GPS-synchronized real-time simulator. The simulated PMUs are used to validate two applications for the real-time protection and control of electrical networks by means of synchrophasor technology. The first one is a protection scheme that relies on PMU-based real-time state estimation processes to detect a fault and identify the faulted line. Then, we validate in a real-time hardware-in-the-loop (HIL) setup, the Grid Explicit Congestion Notification (GECN) voltage control mechanism for distribution networks, already presented in the literature. We show that, by leveraging on the accurate knowledge of the system state, GECN is able to control the state of the system in time-scales of seconds, in order to maintain its voltage level within predefined limits.

This paper introduces a novel approach for power system fault diagnosis based on synchronized phasor measurements during the fault. The synchronized measurements are obtained in real time from Phasor Measurement Units (PMUs) and compared with offline thresholds determined by decision trees (DTs) to diagnose the fault. The DTs have already been trained offline using detailed power system analysis for different fault cases. While the traditional methods for fault diagnosis use the status of protective relays (PRs) and circuit breakers (CBs) to infer the fault section in the power system, the proposed method uses the available signals following the fault and thus can be trusted even in case of protection system failure. Therefore, fault diagnosis can be achieved successfully especially in blackout situations, where many CBs and and/or PRs malfunction. Simulation results on the IEEE 118-bus test system show that the proposed method is highly accurate in wide area fault diagnosis in spite of incomplete system observability.

This paper presents the assessment methodology for voltage stability using Phasor Measurement Unit (PMU) with complete system observability. For full power system observability, the PMU placement is considered with and without conventional power flow as well as injection measurement such that minimum number of PMU's is used. Data obtained by PMU's are used for voltage stability assessment with the help of L-Index. As the PMU gives real time voltage and current phasors and L-index is dependent on voltage and admittance values, thus the L-index so obtained can be used as real time voltage stability indicator. The case study has been carried out on IEEE-14 bus system.