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24 pages, 7708 KiB

Open AccessArticle

Optimal Placement, Sizing and Coordination of FACTS Devices in Transmission Network Using Whale Optimization Algorithm

by Muhammad Nadeem, Kashif Imran, Abraiz Khattak, Abasin Ulasyar, Anamitra Pal, Muhammad Zulqarnain Zeb, Atif Naveed Khan and Malhar Padhee

Energies 2020, 13(3), 753; https://doi.org/10.3390/en13030753 - 08 Feb 2020

Cited by 58 | Viewed by 6658

Abstract

Flexible AC Transmission Systems (FACTS) play an important role in minimizing power losses and voltage deviations while increasing the real power transfer capacity of transmission lines. The extent to which these devices can provide benefits to the transmission network depend on their optimal [...] Read more.

Flexible AC Transmission Systems (FACTS) play an important role in minimizing power losses and voltage deviations while increasing the real power transfer capacity of transmission lines. The extent to which these devices can provide benefits to the transmission network depend on their optimal location and sizing. However, finding appropriate locations and sizes of these devices in an electrical network is difficult since it is a nonlinear problem. This paper proposes a technique for the optimal placement and sizing of FACTS, namely the Thyristor-Controlled Series Compensators (TCSCs), Shunt VARs Compensators (SVCs), and Unified Power Flows Controllers (UPFCs). To find the optimal locations of these devices in a network, weak buses and lines are determined by constructing PV curves of load buses, and through the line stability index. Then, the whale optimization algorithm (WOA) is employed not only to find an ideal ratings for these devices but also the optimal coordination of SVC, TCSC, and UPFC with the reactive power sources already present in the network (tap settings of transformers and reactive power from generators). The objective here is the minimization of the operating cost of the system that consists of active power losses and FACTS devices cost. The proposed method is applied to the IEEE 14 and 30 bus systems. The presented technique is also compared with Genetic Algorithm (GA) and Particle Swarm Optimization (PSO). The findings showed that total system operating costs and transmission line losses were considerably reduced by WOA as compared to existing metaheuristic optimization techniques. Full article

(This article belongs to the Special Issue Electric Power Systems Research 2019)

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15 pages, 12461 KiB

Open AccessEditor’s ChoiceArticle

Fault Analysis and Design of a Protection System for a Mesh Power System with a Co-Axial HTS Power Cable

by Thai-Thanh Nguyen, Woon-Gyu Lee, Hak-Man Kim and Hyung Suk Yang

Energies 2020, 13(1), 220; https://doi.org/10.3390/en13010220 - 02 Jan 2020

Cited by 6 | Viewed by 2970

Abstract

The uses of high-temperature superconducting (HTS) cables pose a challenge of power system protection since the impedance of the HTS cable is varied during fault conditions. The protection systems should be designed properly to ensure the reliability and stability of the whole system. [...] Read more.

The uses of high-temperature superconducting (HTS) cables pose a challenge of power system protection since the impedance of the HTS cable is varied during fault conditions. The protection systems should be designed properly to ensure the reliability and stability of the whole system. This paper presents a fault analysis of the co-axial HTS cable in the mesh system and proposes a coordinated protection system. In the proposed protection system, the main protection is the differential current relay whereas the backup protections are the overcurrent and directional overcurrent relays. The normal and abnormal relay operations are considered to analyze the transient fault current in the HTS cable and evaluate the performance of the proposed coordinated protection system. Characteristics of cable impedances and temperatures under various fault conditions are presented. The proposed protection scheme is validated by the simulation in the PSCAD/EMTDC program. Simulation results show that the coordinated protection scheme could successfully protect the HTS cables in both normal and abnormal relay operations. Full article

(This article belongs to the Special Issue Electric Power Systems Research 2019)

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18 pages, 5607 KiB

Open AccessArticle

A Speed-Governing System Model with Over-Frequency Protection for Nuclear Power Generating Units

by Li Wang, Wentao Sun, Jie Zhao and Dichen Liu

Energies 2020, 13(1), 173; https://doi.org/10.3390/en13010173 - 31 Dec 2019

Cited by 11 | Viewed by 4802

Abstract

Overspeed is more likely to occur in the process of load rejection or large disturbances for nuclear steam turbines due to the large parameter range and low steam parameters, as well as the power of the low-pressure cylinder accounting for a high proportion [...] Read more.

Overspeed is more likely to occur in the process of load rejection or large disturbances for nuclear steam turbines due to the large parameter range and low steam parameters, as well as the power of the low-pressure cylinder accounting for a high proportion of the total power. It is of great significance to study the overspeed characteristics of nuclear power plants (NPPs) to ensure the safe and stable operation of the unit and power grid. According to the characteristics of NPPs, the overspeed protection model and the super-acceleration protection model were established, which were added to the speed-governing system model. The response characteristics of the reactor, thermal system, steam turbine and speed-governing system in the process of load rejection or large disturbances of the power grid were analyzed and simulated. The results were compared using the simulation software personal computer transient analyzer (PCTRAN). The simulation results showed that quickly closing both the high and medium pressure regulating valves could effectively realize frequency control when load rejection or a large grid disturbance occurred. The over-acceleration protection cooperates with the super-acceleration protection to avoid the repeated opening/closing of the valves due to overspeed protection. This could effectively reduce the impact of large disturbances on the reactor, thermal system, and turbine. Full article

(This article belongs to the Special Issue Electric Power Systems Research 2019)

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23 pages, 4344 KiB

Open AccessArticle

Tie-Line Reserve Power Probability Margin for Day-Ahead Dispatching in Power Systems with High Proportion Renewable Power Sources

by Yue Chen, Zhizhong Guo, Abebe Tilahun Tadie, Hongbo Li, Guizhong Wang and Yingwei Hou

Energies 2019, 12(24), 4742; https://doi.org/10.3390/en12244742 - 12 Dec 2019

Viewed by 1895

Abstract

In power systems with a high proportion of renewable power sources (PSHPRPSs), the power constraints of the tie-line may limit the ability of the reserve power to accommodate uncertain power generation, resulting in difficulties for the grid power balance. As uncertain power generation [...] Read more.

In power systems with a high proportion of renewable power sources (PSHPRPSs), the power constraints of the tie-line may limit the ability of the reserve power to accommodate uncertain power generation, resulting in difficulties for the grid power balance. As uncertain power generation cannot be predicted accurately and in accordance with the law of probability and statistics, it is necessary to use a probability model to calculate the uncertain power of the tie-line. Here, day-ahead prediction error probability optimal power flow (DPEPOPF) is proposed to calculate the tie-line reserve power probability margin (TRPPM) in day-ahead dispatching. In day-ahead dispatching, TRPPM is reserved for real-time dispatching to accommodate uncertain power generation, so as to avoid tie-line power congestion. This study classifies the area of the grid based on the principle of area control error accommodation, and the DPEPOPF is divided into two categories: An inter-area day-ahead prediction error probability optimal power flow mathematical model, and an intra-area day-ahead prediction error probability optimal power flow mathematical model. The point estimate optimization algorithm was implemented in MATLAB 8.3.0.532 (R2014a) to calculate the TRPPM. The simulation results verify the accuracy of the model and effectively avoid power congestion of the tie-line. Full article

(This article belongs to the Special Issue Electric Power Systems Research 2019)

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12 pages, 2396 KiB

Open AccessArticle

Vulnerability Assessment of Korean Electric Power Systems to Late-Time (E3) High-Altitude Electromagnetic Pulses

by Soobae Kim and Injoo Jeong

Energies 2019, 12(17), 3335; https://doi.org/10.3390/en12173335 - 29 Aug 2019

Cited by 4 | Viewed by 2529

Abstract

High-altitude electromagnetic pulses (HEMPs) are bursts of electromagnetic energy that result from nuclear weapon detonations at altitudes at or above 30 km. A HEMP is comprised of three components: E1, E2, and E3. E1 and E2 are instantaneous emissions that can damage electronic [...] Read more.

High-altitude electromagnetic pulses (HEMPs) are bursts of electromagnetic energy that result from nuclear weapon detonations at altitudes at or above 30 km. A HEMP is comprised of three components: E1, E2, and E3. E1 and E2 are instantaneous emissions that can damage electronic components, whereas E3 generates low-frequency, geomagnetically-induced currents in transmission lines and power transformers. These currents can lead to the half-cycle saturation of power transformers and increased reactive power consumption. This study assessed the impact of the E3 HEMP on Korean electric power systems. For this assessment, two publicly available E3 HEMP environments were identified. A Direct Current (DC)equivalent model of Korean power systems was developed to calculate the geomagnetically-induced currents and increased the reactive power absorption of transformers in power systems. The vulnerability assessment involved two types of analysis: Static power flow analysis and dynamic transient stability analysis. The maximum electric field limit was determined by performing a steady-state analysis. The capability of the Korean electric power systems to maintain synchronism and acceptable voltages in the transient stability time frame following an E3 HEMP event was evaluated. Furthermore, the effects of detonations at five target locations were compared. It was concluded that Korean electric power systems cannot maintain their stability when affected by an E3 HEMP. Full article

(This article belongs to the Special Issue Electric Power Systems Research 2019)

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18 pages, 13002 KiB

Open AccessArticle

Intelligent Classification Method for Grid-Monitoring Alarm Messages Based on Information Theory

by Guoqiang Sun, Xiaoliu Ding, Zhinong Wei, Peifeng Shen, Yang Zhao, Qiugen Huang, Liang Zhang and Haixiang Zang

Energies 2019, 12(14), 2814; https://doi.org/10.3390/en12142814 - 22 Jul 2019

Cited by 5 | Viewed by 2973

Abstract

Alarm messages for grid monitoring are an important way to supervise the operation of power grids. Since the use of alarm messages is increasing exponentially due to the continuous expansion of the scale of power grids, a processing method for alarm messages based [...] Read more.

Alarm messages for grid monitoring are an important way to supervise the operation of power grids. Since the use of alarm messages is increasing exponentially due to the continuous expansion of the scale of power grids, a processing method for alarm messages based on statistics is proposed in this study. Entropy theory in information theory is introduced into the calculation of information value in power-grid alarming. By means of multiple entropy definitions, an evaluation index system for information value is constructed. Based on the analytic hierarchy process (AHP), various alarm-message entropies are used as indices to comprehensively assess the information value and level of each alarm message. Finally, an example is given to illustrate the effectiveness and practicality of the proposed method. This study provides a new idea for the intelligent classification of alarm messages. Full article

(This article belongs to the Special Issue Electric Power Systems Research 2019)

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16 pages, 1490 KiB

Open AccessArticle

Application of Ordinal Optimization to Reactive Volt-Ampere Sources Planning Problems

by Wen-Tung Lee, Shih-Cheng Horng and Chi-Fang Lin

Energies 2019, 12(14), 2746; https://doi.org/10.3390/en12142746 - 17 Jul 2019

Cited by 7 | Viewed by 2051

Abstract

Reactive volt-ampere sources planning is an effort to determine the most effective investment plan for new reactive sources at given load buses while ensuring appropriate voltage profile and satisfying operational constraints. Optimization of reactive volt-ampere sources planning is not only a difficult problem [...] Read more.

Reactive volt-ampere sources planning is an effort to determine the most effective investment plan for new reactive sources at given load buses while ensuring appropriate voltage profile and satisfying operational constraints. Optimization of reactive volt-ampere sources planning is not only a difficult problem in power systems, but also a large-dimension constrained optimization problem. In this paper, an ordinal optimization-based approach containing upper and lower level is developed to solve this problem efficiently. In the upper level, an ordinal search (OS) algorithm is utilized to select excellent designs from a candidate-design set according to the system’s structural information exploited from the simulations executed in the lower level. There are five stages in the ordinal search algorithm, which gradually narrow the design space to search for a good capacitor placement pattern. The IEEE 118-bus and IEEE 244-bus systems with four load cases are employed as the test examples. The proposed approach is compared with two competing methods; the genetic algorithm and Tabu search, and a commercial numerical libraries (NL) mixed integer programming tool; IMSL Numerical Libraries. Experimental results illustrate that the proposed approach yields an outstanding design with a higher quality and efficiency for solving reactive volt-ampere sources planning problem. Full article

(This article belongs to the Special Issue Electric Power Systems Research 2019)

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16 pages, 5216 KiB

Open AccessArticle

Harmonic Stability Analysis for Multi-Parallel Inverter-Based Grid-Connected Renewable Power System Using Global Admittance

by Wu Cao, Kangli Liu, Shunyu Wang, Haotian Kang, Dongchen Fan and Jianfeng Zhao

Energies 2019, 12(14), 2687; https://doi.org/10.3390/en12142687 - 12 Jul 2019

Cited by 20 | Viewed by 3545

Abstract

Multi-parallel grid-connected voltage source inverters (VSIs) are widely applied in the fields of renewable energy, energy storage, harmonic suppression, etc. However, these inverters may cause harmonic stability problems due to the interactions among the grid-connected inverters through the grid impedance, which can seriously [...] Read more.

Multi-parallel grid-connected voltage source inverters (VSIs) are widely applied in the fields of renewable energy, energy storage, harmonic suppression, etc. However, these inverters may cause harmonic stability problems due to the interactions among the grid-connected inverters through the grid impedance, which can seriously threaten system stability. The impedance-based stability criterion provides an effective tool for analyzing harmonic instability issues and can be divided into two types, namely, a ratio type and a sum type. Based on the existing studies of the sum-type criterion, this paper further proposes a new sum-type form based on the global admittance from the PCC to assess system stability through frequency-domain analysis. This global admittance-based stability criterion can be used not only to analyze system stability, but also to reveal the influence of each VSI unit on system stability with a lower computational burden and provide guidance for resonance suppression, especially in the case of a large number of grid-connected inverters and asymmetric inverter parameters. Finally, a MATLAB/Simulink model and 400 kVA/400 V experimental platform consisting of six grid-connected VSIs were established, and the corresponding results are presented to verify the effectiveness of the proposed method. Full article

(This article belongs to the Special Issue Electric Power Systems Research 2019)

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27 pages, 5240 KiB

Open AccessArticle

Nature-Inspired Whale Optimization Algorithm for Optimal Coordination of Directional Overcurrent Relays in Power Systems

by Abdul Wadood, Tahir Khurshaid, Saeid Gholami Farkoush, Jiangtao Yu, Chang-Hwan Kim and Sang-Bong Rhee

Energies 2019, 12(12), 2297; https://doi.org/10.3390/en12122297 - 16 Jun 2019

Cited by 21 | Viewed by 4376

Abstract

In power systems protection, the optimal coordination of directional overcurrent relays (DOCRs) is of paramount importance. The coordination of DOCRs in a multi-loop power system is formulated as an optimization problem. The main objective of this paper is to develop the whale optimization [...] Read more.

In power systems protection, the optimal coordination of directional overcurrent relays (DOCRs) is of paramount importance. The coordination of DOCRs in a multi-loop power system is formulated as an optimization problem. The main objective of this paper is to develop the whale optimization algorithm (WOA) for the optimal coordination of DOCRs and minimize the sum of the operating times of all primary relays. The WOA is inspired by the bubble-net hunting strategy of humpback whales which leads toward global minima. The proposed algorithm has been applied to six IEEE test systems including the IEEE three-bus, eight-bus, nine-bus, 14-bus, 15-bus, and 30-bus test systems. Furthermore, the results obtained using the proposed WOA are compared with those obtained by other up-to-date algorithms. The obtained results show the effectiveness of the proposed WOA to minimize the relay operating time for the optimal coordination of DOCRs. Full article

(This article belongs to the Special Issue Electric Power Systems Research 2019)

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16 pages, 15339 KiB

Open AccessArticle

Suggestion of a New Protection Scheme for a Transmission System Equipped with a Thyristor-Controlled Series Capacitor

by Minh-Chau Dinh, Minh-Quan Tran, Jae-In Lee, Seok-Ju Lee, Chur Hee Lee, Jongsu Yoon and Minwon Park

Energies 2019, 12(12), 2250; https://doi.org/10.3390/en12122250 - 12 Jun 2019

Cited by 4 | Viewed by 3361

Abstract

A thyristor-controlled series capacitor (TCSC) is employed to a transmission line in order to enhance the usable capacity of the present as well as upgraded lines, improve system stability, reduce losses, and improve power flow control capability. However, in an abnormal situation, the [...] Read more.

A thyristor-controlled series capacitor (TCSC) is employed to a transmission line in order to enhance the usable capacity of the present as well as upgraded lines, improve system stability, reduce losses, and improve power flow control capability. However, in an abnormal situation, the TCSC may transit from the existing operation mode to the other mode according to its control system and protection strategy. There is much difference in the impedance of the TCSC between each mode. This threatens the reliability of the conventional protection system, especially the distance relay, that works based on the measurement of line impedance. In this paper, we suggest a new protection scheme for a distance relay of a transmission line equipped with a TCSC. In the suggested method, in order to mitigate the effect of the TCSC in the fault loop, the TCSC injected voltage is subtracted from the measured phase voltage before supplying the voltage signal to the distance relay. The suggested scheme was verified by a real time digital simulator (RTDS)-based closed-loop test bed of a protective relay. The effect of the TCSC in the fault loop was completely mitigated. The distance relay works properly with the suggested scheme. Full article

(This article belongs to the Special Issue Electric Power Systems Research 2019)

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21 pages, 12067 KiB

Open AccessArticle

Energy Management Optimization and Voltage Evaluation for Residential and Commercial Areas

by Hayder O. Alwan, Hamidreza Sadeghian and Sherif Abdelwahed

Energies 2019, 12(9), 1811; https://doi.org/10.3390/en12091811 - 13 May 2019

Cited by 7 | Viewed by 2688

Abstract

In most smart grids, load management techniques are required to handle multiple loads of several types. This paper studies decentralized demand-side management (DSM) in a grid with different types of appliances in two service areas: one with many residential households, and one bus [...] Read more.

In most smart grids, load management techniques are required to handle multiple loads of several types. This paper studies decentralized demand-side management (DSM) in a grid with different types of appliances in two service areas: one with many residential households, and one bus with commercial customers. Each building runs an individual optimal DSM to reschedule the usage time of its flexible appliances to reduce its electric energy cost at a manageable sacrifice of inconvenience according to the forecasted time-varying electricity price. Using the developed model, we examined the effectiveness of decentralized DSM by comparing its performance on the operation status of the grid in terms of electricity cost saving, rooftop photovoltaic (PV) utilization efficiency, voltage fluctuation, power loss, voltage rises, and reverse power flows, which can easily be seen at the commercial load bus. Full article

(This article belongs to the Special Issue Electric Power Systems Research 2019)

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19 pages, 6099 KiB

Open AccessArticle

Novel Protection Scheme considering Tie Switch Operation in an Open-Loop Distribution System using Wavelet Transform

by Hun-Chul Seo

Energies 2019, 12(9), 1725; https://doi.org/10.3390/en12091725 - 07 May 2019

Cited by 8 | Viewed by 2669

Abstract

Loop power distribution systems are gaining increasing attention due to improvements in the reliability of the power supply and the connection of distributed generation. With loop distribution systems, there is the possibility of mal-operation of the protection relay because of the existence of [...] Read more.

Loop power distribution systems are gaining increasing attention due to improvements in the reliability of the power supply and the connection of distributed generation. With loop distribution systems, there is the possibility of mal-operation of the protection relay because of the existence of the tie switch and bi-directional current injection. In this paper, we propose a novel protection scheme considering the tie switch operation in the open loop power distribution system using wavelet transform. We analyze the possibility of mal-operation of the protection relay as a result of the normal load current after tie switch operation and analyze the characteristics of the normal load current and fault current injection after tie switch operation. Using these results, a new index is proposed to distinguish the normal load current and fault current, and a novel protection scheme based on this new index is proposed. The proposed method is modeled using an electromagnetic transients program and MATLAB, and the various simulations are performed according to the tie switch position, the fault location, and the success or failure of the fault section separation. From the simulation results, we can confirm that the normal load current and the fault current after tie switch operation can be accurately distinguished and the protection relay can accurately operate at only fault conditions. Full article

(This article belongs to the Special Issue Electric Power Systems Research 2019)

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14 pages, 2648 KiB

Open AccessArticle

A Simplified Model of Coaxial, Multilayer High-Temperature Superconducting Power Cables with Cu Formers for Transient Studies

by Thai-Thanh Nguyen, Woon-Gyu Lee, Seok-Ju Lee, Minwon Park, Hak-Man Kim, DuYean Won, Jaeun Yoo and Hyung Suk Yang

Energies 2019, 12(8), 1514; https://doi.org/10.3390/en12081514 - 22 Apr 2019

Cited by 20 | Viewed by 3642

Abstract

Bypassing transient current through copper (Cu) stabilizer layers reduces heat generation and temperature rise of high-temperature superconducting (HTS) conductors, which could protect HTS cables from burning out during transient conditions. The Cu layer connected in parallel with HTS tape layers impacts current distribution [...] Read more.

Bypassing transient current through copper (Cu) stabilizer layers reduces heat generation and temperature rise of high-temperature superconducting (HTS) conductors, which could protect HTS cables from burning out during transient conditions. The Cu layer connected in parallel with HTS tape layers impacts current distribution among layers and variations of phase resistance in either steady-state or transient conditions. Modeling the multilayer HTS power cable is important for transient studies. However, existing models of HTS power cables have only proposed HTS cables without the use of a Cu-former layer. To overcome this problem, the authors proposed a multilayer HTS power cable model that used a Cu-former layer in each phase for transient study. It was observed that resistance of the HTS conductor increased significantly in the transient state due to a quenching phenomenon, which made the transient current mainly flow into the Cu-former layers. Since resistance of the Cu-former layer has a significant impact on the transient current, detailed modeling of the Cu-former layer is described in this study. The feasibility of the developed HTS cable model is evaluated in the PSCAD/EMTDC program. Full article

(This article belongs to the Special Issue Electric Power Systems Research 2019)

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22 pages, 683 KiB

Open AccessArticle

Risk Based Maintenance in the Hydroelectric Power Plants

by Evrencan Özcan, Rabia Yumuşak and Tamer Eren

Energies 2019, 12(8), 1502; https://doi.org/10.3390/en12081502 - 20 Apr 2019

Cited by 26 | Viewed by 6410

Abstract

In this study, maintenance planning problem is handled in one of the hydroelectric power plants which directly affect Turkey’s energy supply security with a fifth share in the total generation. In this study, a result is obtained by taking into consideration the multi-objective [...] Read more.

In this study, maintenance planning problem is handled in one of the hydroelectric power plants which directly affect Turkey’s energy supply security with a fifth share in the total generation. In this study, a result is obtained by taking into consideration the multi-objective and multi-criteria structure of the maintenance planning in the hydroelectric power plants with thousands of complex equipment and the direct effect of this equipment on uninterrupted and low-cost electricity generation. In the first stage, the risk levels of the equipment in terms of the power plant are obtained with the combination of AHP (Analytical Hierarchy Process) and TOPSIS (technique for order preference by similarity to ideal solution) which are frequently used in the literature due to their advantages. Department-based maintenance plans of all equipment for periodic and revision maintenance strategies are formed by integrating these values into the time allocated for maintenance and the number of employees constraints. As a result of the application of this methodology which is designed for the first time in the literature with the integration of multi-criteria decision-making methods for the maintenance planning problem in a hydroelectric power plant, all elements that prevent the sustainable energy supply in the power plant are eliminated. Full article

(This article belongs to the Special Issue Electric Power Systems Research 2019)

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18 pages, 2587 KiB

Open AccessArticle

Short-Term Load Dispatching Method for a Diversion Hydropower Plant with Multiple Turbines in One Tunnel Using a Two-Stage Model

by Shengli Liao, Hongye Zhao, Gang Li and Benxi Liu

Energies 2019, 12(8), 1476; https://doi.org/10.3390/en12081476 - 18 Apr 2019

Cited by 9 | Viewed by 3137

Abstract

Short-term load dispatching (STLD) for a hydropower plant with multiple turbines in one tunnel (HPMTT) refers to determining when to startup or shutdown the units of different tunnels and scheduling the online units of each tunnel to obtain optimal load dispatch while simultaneously [...] Read more.

Short-term load dispatching (STLD) for a hydropower plant with multiple turbines in one tunnel (HPMTT) refers to determining when to startup or shutdown the units of different tunnels and scheduling the online units of each tunnel to obtain optimal load dispatch while simultaneously meeting the hydraulic and electric system constraints. Modeling and solving the STLD for a HPMTT is extremely difficult due to mutual interference between units and complications of the hydraulic head calculation. Considering the complexity of the hydraulic connections between multiple power units in one tunnel, a two-phase decomposition approach for subproblems of unit-commit (UC) and optimal load dispatch (OLD) is described and a two-stage model (TSM) is adopted in this paper. In the first stage, an on/off model for the units considering duration constraints is established, and the on/off status of the units and tunnels is determined using a heuristic searching method and a progressive optimal algorithm. In the second stage, a load distribution model is established and solved using dynamic programming for optimal load distribution under the premise of the on/off status of the tunnel and units in the first stage. The proposed method is verified using the load distribution problem for the Tianshengqiao-II reservoir (TSQII) in dry season under different typical load rates. The results meet the practical operation requirements and demonstrate the practicability of the proposed method. Full article

(This article belongs to the Special Issue Electric Power Systems Research 2019)

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15 pages, 3007 KiB

Open AccessArticle

Adaptive Phasor Estimation Algorithm Based on a Least Squares Method

by Woo-Joong Kim, Soon-Ryul Nam and Sang-Hee Kang

Energies 2019, 12(7), 1387; https://doi.org/10.3390/en12071387 - 10 Apr 2019

Cited by 5 | Viewed by 3439

Abstract

This paper proposes an adaptive phasor estimation algorithm based on a least square method that can suppress the adverse effect of an exponentially decreasing DC offset component in a phasor estimation process. The proposed algorithm is composed of three stages: a basic least [...] Read more.

This paper proposes an adaptive phasor estimation algorithm based on a least square method that can suppress the adverse effect of an exponentially decreasing DC offset component in a phasor estimation process. The proposed algorithm is composed of three stages: a basic least squares model, a time constant calculation, and an adaptive least squares model. First, we use the basic least squares model to estimate the parameter of the DC offset component in the fault current signal. This model is designed to incorporate fundamental frequency, and harmonic and constant components. Second, we use the estimated parameter to calculate the time constant of the DC offset component. Third, we redesign a least squares model that incorporates fundamental frequency, harmonic components, and exponential function of the DC offset component. Since this model incorporates the exponential function of the DC offset component contained in the fault current signal, it estimates the phasor of the correct fundamental frequency component without influence of the DC offset component. We evaluated the performance of the proposed algorithm using computer generated signals and EMTP simulation signals. The evaluation results show that the proposed algorithm can effectively suppress the adverse influence of the exponentially decaying DC offset component. Full article

(This article belongs to the Special Issue Electric Power Systems Research 2019)

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23 pages, 2407 KiB

Open AccessReview

A Comprehensive Survey on Phasor Measurement Unit Applications in Distribution Systems

by Mojgan Hojabri, Ulrich Dersch, Antonios Papaemmanouil and Peter Bosshart

Energies 2019, 12(23), 4552; https://doi.org/10.3390/en12234552 - 29 Nov 2019

Cited by 72 | Viewed by 6100

Abstract

Synchrophasor technology opens a new window for power system observability. Phasor measurement units (PMUs) are able to provide synchronized and accurate data such as frequency, voltage and current phasors, vibration, and temperature for power systems. Thus, the utilization of PMUs has become quite [...] Read more.

Synchrophasor technology opens a new window for power system observability. Phasor measurement units (PMUs) are able to provide synchronized and accurate data such as frequency, voltage and current phasors, vibration, and temperature for power systems. Thus, the utilization of PMUs has become quite important in the fast monitoring, protection, and even the control of new and complicated distribution systems. However, data quality and communication are the main concerns for synchrophasor applications. This study presents a comprehensive survey on wide-area monitoring systems (WAMSs), PMUs, data quality, and communication requirements for the main applications of PMUs in a modern and smart distribution system with a variety of energy resources and loads. In addition, the main challenges for PMU applications as well as opportunities for the future use of this intelligent device in distribution systems will be presented in this paper. Full article

(This article belongs to the Special Issue Electric Power Systems Research 2019)

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