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Summary: Integration of a series capacitor in a transmission line not only has advantages such as system stability and power factor improvements, voltage profile regulation, and power flow maximization but also shows some unwanted effects such as current and voltage inversion, change in line impedance, and subharmonic frequency that leads to mal‐operation of the conventional protection scheme. This paper introduces a fault detection method for a series‐compensated line. An algorithm is proposed that uses the extracted DC component of currents at both sending and receiving ends to detect the fault and generate a trip signal. The proposed protection criterion is successfully examined for diversified (adverse) conditions using PSCAD/EMTDC simulations. [ABSTRACT FROM AUTHOR]

Summary: Objectives: This paper explores the performance of the Single Machine Infinite Bus (SMIB) power system integrating a Photovoltaic (PV) generator when compensated by the Thyristor Controlled Series Capacitor (TCSC) and the Static Synchronous Series Compensation (SSSC) Flexible Alternating Current Transmission System (FACTS) devices. Method: The analysis is performed after the introduction of a step change in the mechanical input and excitation voltage of the synchronous generator connected in parallel with the PV generator at different levels of solar intensity. Time domain simulations based on a non‐linear dynamic mathematical model are used for numerical simulations. Results: The simulation results demonstrated the effectiveness of the addition of TCSC and SSSC FACTS devices to improve the power transfer capacity of the SMIB power system with a PV generator. Conclusion: The response of TCSC and SSSC is almost similar. Nevertheless, the introduction of the two FACTS devices does not achieve a system stable operation at 50% of the total level of solar irradiance. TCSC is more effective than SSSC in maintaining the stability of the system. [ABSTRACT FROM AUTHOR]

Summary: This paper demonstrates the functionality and control of the gate‐controlled series capacitor (GCSC), a new FACTS device composing a pair of antiparallel GTOs in parallel with a fixed capacitor, to mitigate subsynchronous resonance (SSR) in a thermal generation plant connected to a series compensated transmission line. Firstly, by the use of both small‐signal stability analysis and time‐domain simulation, it is revealed that the studied system compensated by the series fixed capacitor is potentially unstable due to the first torsional mode. Then, in order to take benefits of series compensation without the risk of SSR, the fixed capacitor is replaced by GCSC. The capability and effectiveness of the GCSC to damp SSR are validated using modal analysis and time‐domain simulation. Furthermore, GCSC is used in conjunction with a fixed series capacitor to minimize the overall cost of compensation. For this purpose, unlike previous studies, a linear controller is used to stabilize the system. In this study, the IEEE First Benchmark Model is considered as a case study, and MATLAB/Simulink is used as a tool for modeling and design of the control system. Also, time‐domain simulations are done using PSCAD/EMTDC. [ABSTRACT FROM AUTHOR]

Summary: The interconnection between the grid and nonconventional energy sources has become more essential due to the huge rise in energy demand. In the case of wind energy, the grid integration undergoes lots of stability issues. The long‐distance transmission lines are preferred since the wind farms are positioned far from the grid. However, this lowers the bulk power transfer ability of the line. The simple solution to enhance the power transfer capacity is the insertion of series capacitor in the line. However, the frightening factor in inserting the series capacitor is subsynchronous resonance (SSR) oscillations which can lead to shaft fatigue between turbine and generator set. This paper focuses on the analysis of SSR in series‐compensated doubly fed induction generator (DFIG)–based wind energy conversion systems (WECSs). The detailed mathematical modelling of DFIG‐based wind turbine generator (WTG) in state space form which is essential for SSR analysis is explained. The proposed model is found to be more accurate as it includes the dynamics of the rotor‐side converter (RSC) and grid‐side converter (GSC). The influence of series capacitive compensation in a WECs is dealt by employing eigenvalue approach. The developed model is embedded with RSC and GSC controllers for analyzing SSR effect for different operating conditions such as wind speed variations and varying compensation levels using MATLAB/SIMULINK. Also, the scaled‐down model of a 2‐MW wind turbine is deployed in laboratory using a grid‐integrated, series‐compensated 1.1‐kW DFIG machine to realize the influence of series capacitive compensation. It is found that the stability of SSR is affected by different wind velocities and capacitive compensation levels. [ABSTRACT FROM AUTHOR]

Summary: During thunder storms, multilocation faults may occur at different locations in different phases of the 3 phase transmission lines at same or different time. This paper proposes an artificial neural network‐based solution to locate the multilocation faults in double‐circuit series capacitor compensated transmission lines (SCCTLs), unlike previous works that only locate the fault at single location. Although various fault location schemes have been proposed for normal shunt faults occurring at 1 location in SCCTL, nevertheless, finding the locations of multilocation faults in double circuit SCCTL has not been addressed so far. The proposed artificial neural network‐based method determines the location of multilocation faults by using current and voltage signals of 1 end of line only, thus avoiding the need of communication link. The signals are preprocessed by using discrete wavelet transform. A comparative study of various neural networks such as feed‐forward back‐propagation network with Levenberg‐Marquardt algorithm, Elman recurrent neural network with gradient descent algorithm, radial basis function neural network has been carried out. The proposed method is not affected by variation in different parameters viz. fault type, fault location, fault inception angle, fault resistance, degree of series compensation, and location of series capacitor. The key advantage of the method is that it correctly estimates the locations of multilocation faults as well as single‐location fault, thus making it more reliable and accurate as compared to conventional fault location schemes. [ABSTRACT FROM AUTHOR]

A distribution network with distributed generation (DG) is usually called an active distribution network. The voltage quality in an active distribution network tends to degrade because of the bidirectional power flow in the network and the random output characteristic of DG. Existing voltage control methods cannot effectively address this issue. In this article, an improved differential evolution (DE) algorithm-based optimal series compensation voltage control method for an active distribution network is presented. It is assumed that the series compensating voltage is produced flexibly by modern power electronics equipment. The quantitative relationship connecting the node voltage deviation, network power loss and compensating voltage is analysed. The optimal control model, including the power loss and load node voltage, is constructed. Then an improved DE algorithm is proposed to solve the optimal model, which combines the standard DE approach with the simulated annealing and adaptive mutation operator method. The optimal control model can be solved effectively by the improved algorithm. A simulation model is developed based on the IEEE 33 standard distribution network with DG. Simulation results confirm the validity of the optimal control model and the advantages of the improved DE algorithm. [ABSTRACT FROM AUTHOR]

In this paper, a fuzzy logic-based supplementary controller has been developed for the Static VAR System (SVS) to damp torsional oscillations due to subsynchronous resonance (SSR) in a series compensated power system. The performance of the proposed controller has been tested on the IEEE second bench mark model for SSR studies. Time domain simulation has been carried out in a Matlab/Simulink environment. The results show that the conventional proportional integral voltage controller of SVS is not sufficient to damp SSR torsional oscillations, and significant damping of torsional oscillations has been achieved with the proposed fuzzy logic supplementary controller. Copyright © 2014 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

SUMMARY Sub-synchronous resonance (SSR) is a frequent adverse phenomenon in series-compensated lines, threatening either or both mechanical facilities and power system stability. It is widely accepted that flexible AC transmission system (FACTS) can provide an effective solution to relieve the SSR. On the other hand, the advent of distributed FACTS (D-FACTS) technology has led to more economical deployment of the flexible devices in the power system control. This article focuses on verifying the capability of the distributed power flow controller (DPFC) to alleviate the SSR. As a member of the D-FACTS family, the DPFC operates in the same way as the unified power flow controller (UPFC). Compared with UPFC, the DPFC has some advantages like higher control capability, lower price, and more reliability. The DPFC impact on SSR mitigation is interrogated in various case studies, namely, with the SSR damping (SSRD) controller on the series converter, with SSRD controller on the shunt converter and with both simultaneously operating. The best case for SSR mitigation is achieved when the DPFC is supplied with two SSRD controllers concurrently. Simulations are carried out with Power Systems Computer Aided Design/ Electromagnetic Transients including DC (PSCAD/EMTDC) on the Institute of Electrical and Electronics Engineers (IEEE) first SSR benchmark model aggregated with DPFC on the transmission line. Furthermore, a comparison between the SSRD controller on DPFC converters and the supplementary excitation damping controller or the conventional power system stabilizer is also carried out. Copyright © 2012 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Summary: Series compensation improves the power transfer capability and the stability of a transmission system. Inclusion of series compensating devices along with their protecting equipment introduces the problems to conventional protective relaying during power system faults. In this paper, a new protection strategy is proposed based on the instantaneous active and reactive power variations. The applicability of the proposed method to a series compensated transmission system is studied with numerous fault cases. Instantaneous power quantities are measured, and respective active and reactive power quantities are reproduced onto a two‐dimensional coordinated system with reactive power as ordinate and active power as abscissa. The locus of ordered pair of instantaneous power quantities (p(t), q(t)) forms a P‐Q trajectory. The quadrant in which the starting point of P‐Q trajectory (p0(t), q0(t)) lies is computed and taken as reference. This P‐Q portrait is analyzed to detect the fault depending on the condition that the operating point shifts its quadrant under fault condition. Fault will be classified based on the polarities of extracted powers. Classification tree is formed by a set of yes/no consequences to classify the fault. The proposed method is tested for different types of faults, at distinct locations and fault inceptions on 500‐kV, 50‐Hz test system. Results thus obtained show the potentiality of proposed strategy for the protection of series compensated transmission system concerning the speed, computational burden, and mathematical complexity. [ABSTRACT FROM AUTHOR]

Summary: This paper proposes a nonlinear controller based on state feedback linearization (SFL) method to mitigate sub‐synchronous control interaction (SSCI) in series‐compensated doubly fed induction generator (DFIG)‐based wind power plants (WPPs). To make full use of the converter control of DFIG, the SFL controller is developed for both grid side converter (GSC) and rotor side converter (RSC) through four necessary steps, ie, assessment of the feedback linearizability, coordinate transformation, feedback linearization, and derivation of control laws. The stability of the internal dynamics, which is not transformed into linear autonomous subsystems in the design process of the RSC controller, is ensured by the application of zero‐dynamic theory. A 100‐MW DFIG‐based WPP adapted from the IEEE first benchmark model is utilized to evaluate the effectiveness of the SFL damping controller at different wind speeds and compensation levels, and the capability of the proposed controller in mitigating SSCI is compared with a well‐tuned proportional‐integral controller and a conventional SSCI damping controller. The superior performance of the SFL controller is demonstrated at varied operating conditions through frequency scanning analysis, eigenvalue analysis, and electromagnetic transient simulation. Moreover, the robust stability of the proposed controller is guaranteed under parameter uncertainties using μ analysis. [ABSTRACT FROM AUTHOR]