A Closed-Loop Parameter Estimation Solution for Fixed Series Compensated Transmission Lines

Conventional control techniques such as proportional integral (PI) control and proportional integral derivative (PID) control are widely used as the load frequency controller in power system control applications; however, the increase in complexity of the power system is degrading the performance of classical control. Therefore, in this paper a new control approach using fractional calculus has been proposed for the load frequency control problem of two-area hydro-thermal power system. The paper presents an interconnected hydro-thermal power system working under different operating conditions introduced in the form of various nonlinearities. Four case studies have been presented in this paper considering transient analysis with (i) different loading conditions, (ii) parameter variations, (iii) different nonlinearities (governor dead band nonlinearity, time delay and generation rate constraints), and (iv) superconducting magnetic energy storage (SMES) device. A tilt integral derivative (TID) control has been presented as a secondary controller to stabilize the frequency deviations occurring in the two-area power system with the above-mentioned different operating conditions. The parameters of TID controller have been optimized using a differential evolution algorithm which solves an optimization problem formulated using the integral of time-weighted absolute error (ITAE) performance index. In addition, a comparison of dynamic system response obtained using TID control and PID control has been presented, which focusses on the better performance of TID control over PID control in an interconnected power system.

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.

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.

Distributed Generation is generation of electricity from renewable energy resources, located closer to the customers or loads. Installation of Distributed Generation could improve voltage and power quality, mitigate voltage sags, minimize transmission system congestion, and provide more affordable capacity for utilizing renewable energy resources. However, high penetration of Distributed Generation to the existing national grid system may contribute several impacts including fault level, as well as the performance of power system protection. Monitoring of fault level is important in power system protection in order to sustain the health of power system networks. This paper investigates the impact of installing Distributed Generation to power system fault level. Three-phase symmetrical fault is simulated and analyzed for various sizes of distributed generation in IEEE 30 bus system using Power System Simulation for Engineering (PSS/E) software.<p class="MsoNormal" style="text-align: justify; text-indent: .5in;"><em><span style="font-size: 9.0pt; font-family: 'Arial','sans-serif'; color: black;">Distributed Generation is generation of electricity from renewable energy resources, located closer to the customers or loads. Installation of Distributed Generation could improve voltage and power quality, mitigate voltage sags, minimize transmission system congestion, and provide more affordable capacity for utilizing renewable energy resources. However, high penetration of Distributed Generation to the existing national grid system may contribute several impacts including fault level, as well as the performance of power system protection. Monitoring of fault level is important in power system protection in order to sustain the health of power system networks. This paper investigates the impact of installing Distributed Generation to power system fault level. Three-phase symmetrical fault is simulated and analyzed for various sizes of distributed generation in IEEE 30 bus system using Power System Simulation for Engineering (PSS/E) software.</span></em></p><!--[if gte mso 9]><xml>
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Guest Editorial: Situational awareness of integrated energy systems

Emerging power system protection and control applications require faster-responding measurements and more accurate knowledge of the actual latency of the measurement and communications systems. A new method for accurately determining the reporting latency of a phasor measurement unit (PMU) has been developed and demonstrated. This method operates in real-time, works passively for any existing PMU without requiring changes to the PMU hardware or software, and it is very accurate-providing a measurement uncertainty of <;500 ns in many cases, significantly surpassing the 0.002 s accuracy requirement in the most recent IEEE Synchrophasor standard. Only low-cost hardware and open source software are required. It is particularly important to understand end-to-end system latency, including the impact of local and wide-area communications, rather than just the latency of the PMU device; the proposed method also supports such practical measurements. It is therefore shown how this advance can be used to enable efficient, but realistic, cross-domain power system simulation studies, which incorporate measurement and communications delays. These capabilities address complexity and uncertainty in the design and operation of future PMU-based protection and control functions for new smart grid services.

Since phasor measurement units (PMU) were invented, there has been growing interest in developing methodologies for improving monitoring, protection and control of power systems in real time. In this study, the authors propose a new methodology, based on graph modelling, to identify coherent groups of generators in a real‐time fashion. The coherent groups are identified with instantaneous values measured from the system through PMUs, and the methodology needs neither setting the number of desired groups nor defining a threshold value since it is based on coupling factors between generators. Moreover, it is proposed a new method for the online definition of areas for islanding when this action is required as the latest emergency control method. The methodology assigns the non‐generation buses to the previously found generators coherent groups considering three criteria: electrical distance to the group of generators, topology, and operational constraints, which are verified by mean of an optimal power flow. The methodology is tested on the IEEE 39‐bus and IEEE 118‐bus test systems. Results show that the real‐time identification of coherent groups and the definition of areas allow the development of islanding strategies with promising results.

Frequency is an important parameter that plays a crucial role in the monitoring, protection and control of power system. It provides an indication of the interconnection's generation/load balance. Normally nominal frequency is either 50 Hz or 60 Hz in most of the countries. Any deviation of frequency from nominal is an indication of abnormal condition or generation/load imbalance. Synchronized phasor measurement unit (PMUs) are providing a promising future for accurate phasor and frequency estimation. Initially Synchrophasor estimation was the main thrust and after amendments in IEEE standards researchers could able to provide solution for frequency and rate of change of frequency (ROCOF) estimation. The main concern now is to achieve accurate, fast, less computationally complex and economic frequency and ROCOF estimation algorithm. So far different algorithms have been proposed for commercial PMUs and are being claimed as in compliance with IEEE standards C37.118.2011. These standards are providing benchmark for justifying accuracy of commercial PMUs. For effective monitoring and control of these PMUs, their operation under transient and large dynamic oscillation demands quick and highly accurate estimation without any discrepancy in estimated phasor value, irrespective of different manufacturers. This paper presents a comparative analysis of fundamental phasor estimation algorithms namely Basic FFT, Recursive DFT and Non-Recursive DFT under normal operating condition and in presence of noise and harmonics.

Power system automation is heavily dependent on the reliable interconnection of power system field equipment and centralised control applications. Particularly important to achieve reliability in automated power systems is the redundant connection of field equipment controllers. Today, the fundamental redundancy management and switch-over processes are handled by the power system control applications itself. This, however, increases the complexity of the control systems and leads to an intersection of concerns. Consequently, the design and the implementation of field equipment controller redundancy is time-consuming and cost-intensive.In this paper, we propose the implementation of a redundancy virtualisation layer for power system controllers based on software-defined networking (SDN). The goal is to relieve the control applications from managing field level redundancy. Thus, our SDN approach allows to detect gateway failures and to perform transparent switch-overs. This significantly simplifies the configuration of the control application with redundant components and finally leads to more flexible and simplified redundancy design, deployment and operation. Arbitrary redundancy topologies, such as triple-controller-redundancy can be implemented without modifying the control applications.

Synchronized phasor measurements are traced from their origins in computer relaying to present applications in power system operation, protection, and control. The principle behind the measurement technique is reviewed along with the details of phasor measurement units (PMUs). Two IEEE standards, applicable to PMU technology, the 'COMTRADE' standard, and the 'SYNCHROPHASOR' standards are summarized. Applications of PMUs to state estimation, measurement based control, adaptive protection, and a new generation of remedial action schemes are described

In recent years, phasor measurement units (PMUs) as vital elements have been widely increased in control, monitoring and protection of power systems. In practice, as the size of a power system is large, it is not possible to install all PMUs over a short period of time mainly due to the financial and technical barriers. One solution would be installing the PMUs over different stages. Accordingly, the paper presents an effective approach for multistage PMU placement (MSPP) in power systems, called dynamic MSPP. Furthermore, since the probabilistic concept of observability reflects a more realistic image of power system observability compared to deterministic ones, this paper, unlike most of the existing MSPP models, investigates the MSPP model in both probabilistic and deterministic frameworks. Compared to the existing approaches and results, the obtained ones in this paper show a considerable improvement in the observability level during PMU installation period. In the proposed approach, PMUs are installed at intermediate stages aimed at maximizing the cumulative network observability in a single optimization process, instead of several subsidiary optimizations in conventional approaches. Briefly, the proposed approach offers a complete search space for the problem, while the existing models lead to limited ones. Moreover, because of the nonlinearity posed by the probabilistic concept of observability as well as the proposed MSPP, cuckoo search optimization algorithm is used to handle the complexity and a new problem encoding/decoding technique for the proposed MSPP is utilized. Eventually, the suggested framework is implemented on different case studies as well as Iranian Transmission Network to reveal the performance of the presented model.

Frequency is an important parameter in the monitoring, control, and protection of power systems and electric equipment. In this article, based on the adaptive short-time Fourier transform, a new digital algorithm is presented to estimate the frequency of electric signals. The novel window, called the Rectangle Self-Convolution Window, is adapted to eliminate the impact of harmonics, and the window length is adjusted according to the variation of signal frequency. The algorithm is easy to implement with high precision and short response time as well as a wide measuring range. It is thus suitable for real-time detection, especially when the frequency changes abruptly and the signal is corrupted by harmonics. Simulation results and practical application show that it is feasible and effective under different conditions.

One issue that did not get adequate attention regarding control and protection of power systems in the past is the data integration and information exchange. The traditional approaches assume that each function such as protection, control, monitoring, and maintenance are supported by a separate infrastructure of recording instruments and/or controllers for obtaining and processing data. With introduction of the new computer-based equipment for control and protection in the mid eighties, the integration of data and information exchange were possible, but not explored. This paper indicates what are the improvements and benefits that can be obtained by integrating the data and exchanging information among control and protection as well as system-wide monitoring and control functions.

Modern computer communication technologies make it possible to create very flexible Data delivery service (DDS) design that can efficiently meet the quality-of-service needs of a wide variety of power system control and monitoring applications, some which only become possible with better communications. One aspect of the smart grid is that multiple applications will use data from each location. Furthermore, the use of the data for important power grid control functions requires each message's source be authenticated, leading to the need for multicast message authentication. All known multicast message authentication approaches carry trade-offs between quality-of-service (QoS) aspects such as added latency, computational cost, and the precise authentication guarantees they afford. This paper surveys several multicast authentication approaches for use in a power grid DDS based on an experimental evaluation of their latency and computational costs and an assessment of the appropriateness of their authentication guarantees for use in power grid applications.

Phasor Measurement Units (PMUs) have potential role in power system monitoring, protection and control. PMUs directly measure and provide synchronized measurements of voltage and current phasors at various system locations. This offer numerous possibilities for ascertaining information related to the state and health of a power system. The aim of an optimal PMU placement is to provide minimal PMU installations to ensure complete observability of a power system. Several methods have been proposed in the past and significant work has been carried out till date to ensure observability of transmission networks. Penetration of new technologies at distribution level raises concern about system operation. These concerns can be addressed by synchrophasor applications. Hence, PMUs play an equally important role at distribution level also. Since, distribution systems are large in size as compared to transmission systems, the algorithms reported may take longer computational time for optimization. Hence, an approach towards optimal PMU placement for distribution system is required. This paper presents a simple and effective algorithm of PMU placement for distribution networks that saves considerable amount of computational time. The proposed algorithm is tested on IEEE-13, 34 and 123 Node Test Feeders and results show that computational time is considerably reduced without significantly affecting the number of PMUs.