A Machine Learning Approach to the Identification of Voltage Control Area Using Synchrophasor Measurements

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.

Several major blackouts in the past have shown the need for advanced wide‐area monitoring and control (WAMC) techniques. Advanced synchrophasor visualization and monitoring can be realized with time‐referenced power system data that are collected by phasor measurement units (PMUs) using synchronized clocks. Presently, PMUs are being deployed around the world at a rapid rate for various power system applications. When a necessary number of PMUs are installed at optimal locations throughout the network, the complete state of the system can be observed. PMUs take real‐time measurements to determine the state of the power system and can be used to enhance state estimation efficiency. With PMUs in place, there are many control and protection schemes that can be implemented successfully to take preventive and corrective actions. These remedial action schemes (RASs) are classified by the IEEE Power System Relaying Committee (PSRC) as system integrity protection schemes (SIPSs). This work involved the development of a real‐time hardware test bed in order to analyze the transient stability of a simulated power system by using synchrophasors to visualize system stress across a transmission line with and without load‐shedding schemes. The real time digital simulator (RTDS®) was used to model the power system in real time. PMUs, a satellite‐synchronized clock, and a synchrophasor vector processor (SVP) were used to test the synchrophasor application. Copyright © 2010 John Wiley & Sons, Ltd.

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.

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.

Synchronized phasor measurement has gained wide acceptance in many power system applications, particularly for tracking dynamic transitions during various disturbances. Fourier filter-based phasor estimation algorithms, which have been predominately used in phasor measurement units, have difficulties in processing dynamic sinusoidal waveform distortions, such as modulation, frequency drift, abrupt change in magnitude, etc. This paper proposes an adaptive approach for accurately estimating phasors while eliminating the effect of various transient disturbances on voltages and currents. The method preanalyzes the waveform spanning the window of observation to identify and localize the discontinuities which affect the accuracy of phasor computation. A quadratic polynomial signal model is used to improve the accuracy of phasor estimates during power oscillations. Extensive experimental results demonstrate the advantages. The method was implemented on a PC-based PXI system for real-time phasor computations. It can also be used as reference algorithm for testing the performance of the devices extracting synchronized phasor measurements.

Synchronized Phasor Measurement Units (PMUs) are becoming a key element of monitoring, protection, control and state estimation applications in power systems and are the basis for the implementation of Wide Area Monitoring Systems (WAMSs). This paper investigates the possibility of using a software-only PTP (Precision Time Protocol) synchronization method to synchronize different Phasor Measurement Units (PMUs) and how this synchronization impacts the State Estimation. In this context, as a case study, the output data of the PMUs have been used to estimate the state of a power system of reduced size and complexity. A laboratory experimental setup has been built to evaluate the performance achievable with the proposed synchronization solution. The results thus obtained and the performance analysis are discussed in this paper.

Nowadays, the increase in electrical energy consumption and power system restructuring have posed new challenges to the operation, control, and monitoring of power systems. In this situation, the supervisory control and data acquisition (SCADA) system is not enough to ensure power system security and stability. The SCADA is often unable to measure data of all buses simultaneously. In addition, the sampling rate in this system is not enough for some power system applications. Therefore, the information obtained from SCADA does not show power system dynamics properly. In order to improve the power system monitoring, wide area measurement system (WAMS) has been developed to overcome the problems of SCADA system. Phasor measurements units (PMUs) are the main part of WAMS system and it basically consists of three essential processes including collecting, transmitting, and analyzing data. WAMS receives obtained data via a high speed communication links. After data processing and extracting appropriate information, decisions are made to improve the power system performance. Efficient use of power system data to achieve a secure operation strategy is targeted using the WAMS system. Due to the effective role of WAMS and PMUs in the reliable operation of power system, it is necessary to study their concept and applications in this chapter. The history of PMU and its structure is presented in this chapter. In addition, the necessity of WAMS for future power system and its difference from SCADA system have been investigated in this chapter. Different algorithms and application of the WAMS are also introduced in this chapter which can be implemented to improve the performance of the future power system.

Application of heuristic algorithms to optimal PMU placement in electric power systems: An updated review

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.

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.

Time synchronized phasors obtained using Phasor Measurement Units (PMU) spread across wide areas have revolutionized power system monitoring and control. These synchronized measurements must be accurate and fast in order to comply with the latest IEEE standards for synchrophasor measurements. The speed at which a PMU provides an output depends on the group delay associated with that PMU and the permissible group delay in-turn decides the utility of a PMU for either control or measurement application. Based on the group delay compensation techniques, in the literature, two individual types of PMUs, such as causal and non-causal PMUs have been introduced. This paper presents an approach where both causal and non-causal PMUs are combined in an integrated PMU architecture. This method not only illustrates the group delay performance of two PMUs in a single module, but also can be used for multiple functions. In this environment several PMU algorithms have been compared with respect to their group delays and their effect on the response time. Application of the integrated PMU architecture to a four-machine 10-bus power system has been demonstrated using a six-input PMU with three-phase voltage and current signals as inputs. Different causal compensation schemes are introduced due to the availability of voltage and current-based frequency and ROCOF signals. Impact of these compensation schemes on PMU accuracy is evaluated through the Total Vector Error (TVE) index. The influence of these compensation schemes on measurements like power and impedance is also investigated. Finally, outputs from the integrated PMU architecture are fed into a Power System Stabilizer (PSS) to control the small-signal stability performance of a power system during dynamic conditions.

Series compensated power system may lead to a very unusual problem known as Subsynchronous Resonance (SSR). Flexible AC Transmission Systems (FACTS) controllers are widely applied to mitigate subsynchronous oscillations. The Static Synchronous Compensator (STATCOM) is a shunt device of the FACTS family using power electronics to control power flow and improve transient stability on power grids. With the advent of Wide Area Measurement (WAM) technology, it is possible to measure the states of a large interconnected power system with synchronized Phasor Measurement Units (PMU). In this paper the concept of using remote signals acquired through PMU has been proposed to damp SSR. An auxiliary subsynchronous damping controller (SSDC) for a STATCOM using the remote accelerating power of generator signal as the stabilizing signal has been designed to damp subsynchronous oscillations. This paper deals with a cascaded multilevel converter model, which is a 48-pulse (three levels) source converter. The voltage source converter described in this paper is a harmonic neutralized, 48-pulse GTO converter. The IEEE Second Benchmark (SBM) model is considered for the analysis and the complete digital simulation of the STATCOM within the power system is performed in the MATLAB/Simulink environment using the Power System Blockset (PSB).

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.

Phasor measurement unit (PMU) is among the most important measurement devices in modern power systems. It measures the voltage and current phasors which have both magnitude and phase angle using a common timing reference. These measurements are utilized in real time applications of electrical power systems. The main drawback of PMUs is its high cost so if PMUs are used to collect or send online real data from a system to a data centre or a decision maker, the used number of PMUs should be minimum with full observability of system measurements. This paper proposes a flower pollination algorithm (FPA) to find the optimal number and locations of PMUs in power systems. The optimization objectives of the work are the minimization of PMUs number, the achievement of complete observability of power system states, and the maximization of measurement redundancy. Existence of zero-injection buses in the system decreases the number of PMUs that is required to fulfil the complete observability of system states. Furthermore, additional constraints for remaining system full observable following failure of single PMU and single line outage are also included to increase the system reliability. The performance and efficiency of the proposed FPA is tested on IEEE standard networks such as 14-bus, 30-bus, 57-bus and 118-bus and new England 39-bus network. The obtained simulation results approve the ability of the proposed optimization method to find the optimal allocation of PMUs in different cases with fulfilling complete observability and reliability of electric power systems. The superiority of FPA is also verified by comparing its results of other optimization algorithms.

The PMU (Phasor Measurement Unit) is used for accurate measurement of synchronous phasor of voltages and currents. Based on synchronous phasor continuous measurement at the different location of distribution network is possible prevent fault which can cause blackout. Synchronous phasor measurement is described in IEEE C37.118-2005 standard. The IEEE C37.118-2005 is primarily focused on communication with the PMU and precision of the measurement at steady state. PMU manufacturers declare compliance with IEEE C37.1182005, which doesn't mean correct behaviour of the PMU for dynamic changes in the power network. The new standard for the PMU is currently developing. This standard should contain both the issues included in IEEE C37.118-2005 and description of PMU testing in connection with dynamic changes in power network. This article deals with the implementation of tests for testing the dynamic properties of PMU. These tests are conducted by tester, which was designed and implemented based on virtual instrumentation. The results of several tests of commercial PMUs are presented in the article. (4 pages)