Application of phasor measurement units for monitoring power system dynamic performance

This Working Group is a sequel to a previous working group on Wide Area Monitoring and Control for Transmission Capability Enhancement, which published the Technical Brochure 330 in 2007. Since then the synchrophasor technology has advanced rapidly and many utilities around the world have installed hundreds of PMUs in their networks. In this Technical Brochure, we look at the current state of the technology and the extent to which it has been used in the industry. As the technology has matured, it is also important to understand the communication protocols used in synchrophasor networks and their relevant cyber-security issues. These concerns are briefly discussed in the brochure. The applications of Phasor Measurement Units (PMU) measurements reported here are divided into three categories: (a) applications already installed in utility networks, (b) applications that are well-tested, but not yet installed, and (c) applications that are beneficial to the industry, but not fully developed yet. The most common and mature applications are wide area monitoring, state estimation, and model validation. Out of these three applications, wide area monitoring is well established in the industry. The protection and control applications are emerging as evident from the reported examples. The experience of using remote synchrophasor measurements as feedback control signals is not widely reported by the industry. In parallel to this Working Group, Study Committee B5 had a Working Group on “Wide area protection and control technologies.” The Technical Brochure 664 published by this Working Group in September 2016 reviews synchrophasor technology and discusses the industry experience with wide area protection and control. The North American synchrophasor Initiative (NASPI) is another technical group that has gathered and reported a wide range of PMU experiences of industry and researchers. In summary, the field-tested applications presented in this Technical Brochure are a testimony to the confidence of utilities in the synchrophasor technology. The progress in state estimation techniques indicates that synchrophasor measurements will become a standard part of energy management and security assessment systems in the near future

An Optimized Space Vector Modulation Sequence for Improved Harmonic Performance

This paper proposes a method for optimization of the harmonic performance of converters under space vector modulation (SVM) control. It is shown that SVM provides a number of degrees of freedom, which make it suitable for optimization, subject to desired constraints. An objective function is defined, which seeks to minimize the most significant harmonic components of the generated waveform while keeping other harmonic components within the acceptable range outlined in the available standards. Since the formulation of the problem involves both real and integer variables, specialized optimization methods capable of handling mixed-integer variables need to be employed, and hence, a genetic algorithm optimizer is used to solve the optimization problem. Optimized SVM sequences obtained for various operating points under different sampling frequencies are shown to result in significant reduction of dominant harmonics while maintaining the waveform quality within prescribed limits

Marginal cost of reliability improvement for standalone microgrids

The marginal cost of reliability improvement (MCRI) is a very useful measure to compare the cost-effectiveness of various standalone microgrid (SMG) systems. This measure helps in decision making on reliability level and imports and exports between SMGs. The MCRI can elucidate how a SMG system is going to deal with the change of reliability requirements by customers and energy traders. This paper proposes an MCRI evaluation algorithm for a microgrid (MG) over its 25-year lifespan. A case study is evaluated, which consists of renewable energy resources (RES) and a battery energy storage system (BESS) as reliability improvement (RI) alternatives. Two sensitivity analysis study are performed to answer the following research questions: What if is the cost of energy resources changes? and What if demand response (DR) is included as an alternative to RI. Furthermore, whether maximum reliability can be achieved with 100% renewable generating resources is also evaluated. The Monte Carlo Simulation (MCS) method is used to model the equipment failure. The linear regression approach is used to create an equation for loss of load reduction (LOLR), for the addition of resource mix as a function of LOLR and for the addition of individual RI alternatives. A Matlab optimization tool is used to find the MCRI

Reliability Evaluation of Renewable-Rich Microgrids Using Monte Carlo Simulation Considering Resource and Equipment Availability

This paper proposes a new reliability evaluation method for renewable energy (RE) rich microgrid (MG) systems using a holistic approach by modelling the availability of renewable resources such as solar irradiation and wind along with the equipment availability during each hour. Where an electric network relies heavily on renewable resources the availability of such resources will significantly affect the reliability of the whole system. In addition, energy storage systems (ESSs) impact the reliability of a microgrid. In this paper, the mean time to failure (MTTF) of a RE rich MG system is evaluated based on the MTTF of equipment for different levels of renewable energy generation and energy storage. The loss of load frequency (LOLF) in each hour due to equipment failure, due to resource unavailbalitly, and the system failure due to combined effects were counted in a simulation study of 25 years

Inductive fault current limiters: A review

© 2020 Elsevier B.V. A fault current limiter (FCL) is an effective means of limiting fault currents that is a promising power system protection solution. This paper presents a comparative survey of research activities and emerging technologies of FCL and discusses in detail the features of an inductive FCL. Inductive FCLs possess superior performance and higher speed of operation in comparison with other FCLs. The magnetic structure of an inductive FCL is instrumental to superior performance. The review study discusses the feasibility and effectiveness of the magnetic flux based FCLs. In addition, the magnetic behavior of FCLs is discussed considering the analytical study of their equivalent circuits. Moreover, a comprehensive comparative study of inductive FCLs is presented based on their technical operational characteristics

Trends in modern power systems resilience: State-of-the-art review

The power system is vital to energy security, emergency services, critical infrastructures, and the economy. Resilience of the power system against high-impact low-probability events is of particular importance to ensure the stability and reliability of the system planning and operation. The challenges and opportunities towards both the evaluation and improvement of resilience of the power system are explicitly reviewed in this paper. Appropriate criteria with a comprehensive understanding of resiliency are emphasized. In addition, to improve the modern power system resilience, this article considers the short and long-term plans with different categorizations, along with a detailed analysis of the corresponding challenges. Short-term plans refer to resilience-oriented scheduling, and long-term plans indicate fundamental corrections such as hardening and equipment upgrades. Practical methods are discussed in the paper to evaluate and improve the modern power system resilience. Furthermore, some common metrics for long-term and short-term resilience assessment are evaluated and compared. The investigations have shown that microgrids have a high potential to improve resilience of the power system by bringing energy sources closer to load centers, and reducing the grid dependence on transmission lines, which are the most vulnerable equipment against natural disasters

Analysis of fault response of inverter-interfaced distributed generators in sequence networks

© 2018 IEEE Microgrids mainly rely on distributed energy resources (DER) unable to generate electricity at the expected voltage and frequency. This necessitates the usage of inverters acting as a conditioning interface between the DER and microgrid, hence the name inverter-interfaced distributed generators (IIDG). On the other hand, the fast response of the primary control of inverters causes unconventional behavior of IIDGs under fault conditions, which can severely affect all parts of relaying, that is, fault sensing and polarization and faulted phase selection. This issue becomes more pronounced when an inverter-based microgrid operates in autonomous mode. This paper analyzes the root causes of such unconventional responses that challenge the traditional protection schemes. At first, the inverter control strategies including current limiting are briefly discussed. Then, the paper is continued by analyzing the response of an IIDG feeding its local load to balanced and unbalanced faults, where MATLAB/SIMULINK is used for simulation studies. It is shown how the constraints set by the control strategy itself and current limiter affect the response of IIDGs to fault conditions and consequently, their equivalent models under fault conditions. The findings presented in the paper clearly show that protective functions face difficulties in coping with fault conditions in IIDG-based microgrids due to their different equivalent models during fault period. These studies in turn help modify existing protection schemes or devise new ones applicable to this concept

Dynamic average-value modeling of direct power-controlled active front-end rectifiers

Active front-end (AFE) rectifiers are becoming widely used in medium-to-high-power adjustable speed drives (ASDs) to achieve regenerative operation and meet the energy efficiency and harmonic requirements. The typical control methods used with AFE rectifiers include voltage-oriented control (VOC), direct power control (DPC) and virtual-flux-based methods. This paper presents a dynamic average-value model (AVM) of the AFE rectifier system which is based on the voltage-sou

Cell-traversal protein for ookinetes and sporozoites (CelTOS) formulated with potent TLR adjuvants induces high-affinity antibodies that inhibit Plasmodium falciparum infection in Anopheles stephensi

Abstract Background Plasmodium falciparum parasite is the most deadly species of human malaria, and the development of an effective vaccine that prevents P. falciparum infection and transmission is a key target for malarial elimination and eradication programmes. P. falciparum cell-traversal protein for ookinetes and sporozoites (PfCelTOS) is an advanced vaccine candidate. A comparative study was performed to characterize the immune responses in BALB/c mouse immunized with Escherichia coli-expressed recombinant PfCelTOS (rPfCelTOS) in toll-like receptor (TLR)-based adjuvants, CpG and Poly I:C alone or in combination (CpG + Poly I:C), followed by the assessment of transmission-reducing activity (TRA) of anti-rPfCelTOS antibodies obtained from different vaccine groups in Anopheles stephensi. Methods The aim of the current work was achieved by head-to-head comparison of the vaccine groups using conventional and avidity enzyme-linked immunosorbent assay (ELISA), immunofluorescence test (IFAT), and standard membrane feeding assay (SMFA). Results Comparing to rPfCelTOS alone, administration of rPfCelTOS with two distinct TLR-based adjuvants in vaccine mouse groups showed a significant increase in responses (antibody level, IgG subclass analysis, avidity, and Th1 cytokines) and was able to induce reasonable transmission-reducing activity. Also, comparable functional activity of anti-rPfCelTOS antibodies was found in group that received antigen in either CpG or Poly I:C (69.9%/20% and 73.5%/24.4%, respectively, reductions in intensity/prevalence). However, the vaccine group receiving rPfCelTOS in combination with CpG + Poly I:C showed a significant induction in antibody titers and inhibitory antibodies in oocysts development (78.3%/19.6% reductions in intensity/prevalence) in An. stephensi. Conclusions A key finding in this investigation is that rPfCelTOS administered alone in BALB/c mouse is poorly immunogenic, with relatively low IgG level, avidity, inhibitory antibodies, and mixed Th1/Th2 responses. However, immunological characteristic (IgG level, cytophilic IgG2a and IgG2b, avidity, and Th1 cytokines) and TRA of anti-rPfCelTOS significantly enhanced in the presence of co-administration of TLR-based adjuvants, confirming that targeting TLRs would be an effective means for the enhancement of inducing TRA against rPfCelTOS