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The phase imbalance compensation concept is proposed in literature as an alternative way to mitigate classical subsynchronous resonance (SSR) problems in series-compensated transmission lines. However, a fundamental analysis to determine this concept’s ability to mitigate resonances between a doubly-fed induction generator (DFIG) and a series compensated transmission line, i.e., DFIG-SSR, is not reported in literature. Therefore, the objective of this paper is to investigate to which extent phase imbalance compensation is able to mitigate DFIG-SSR. For the phase imbalance compensation scheme, an analytical model that captures the relation between the level of series compensation, the degree of asymmetry between the compensated phases, and the resulting shift in resonance frequency is developed and validated using time domain simulations. Then, an optimisation framework is developed to search for an adequate level of compensation asymmetry, capable of mitigating the adverse interactions. The optimisation allows us to show that, even with the best set of parameters, phase imbalance compensation is not suitable for mitigating DFIG-SSR. The analytical model enables us to explain the underlying physical reasons for this and an attempt is made to explain why this concept is theoretically able to mitigate classical resonance issues. Lastly, directions for future research are identified.

The replacement of conventional generation by power electronics-based generation changes the dynamic characteristics of the power system. This results in, among other things, the increased susceptibility to subsynchronous oscillations (SSO). First, this paper discusses three recently emerging SSO phenomena, which arise due to the interactions between (1) a doubly-fed induction generator and a series compensated transmission system; (2) a voltage source converter (VSC) and a weak grid; and (3) nearby VSCs. A fundamental review of these phenomena resulted in the requirement for a reclassification of the existing SSO phenomena. This reclassification is proposed in this work and is based on interacting components identified using participation factor analysis for the distinct phenomena. Second, a critical review of the existing mitigation measures is performed for these phenomena, highlighting the advantages and disadvantages of the solutions. The influence of the wind speed, grid strength, number of wind turbines, and several converter controller parameters are also discussed. To assist equipment manufacturers, control design engineers, and system operators in selecting and designing effective mitigation measures, the existing solutions are categorized in control solutions, hardware solutions, and solutions based on system level coordination. Finally, perspectives on open issues conclude this paper.

The use of compensation networks increases the power transfer capability of inductive power transfer (IPT) systems in the battery charging process of electric vehicles (EVs). Among the proposed topologies, the Series-Series (SS) and the LCC networks are currently in widespread use in wireless battery chargers based on IPT systems. This paper focuses on the study of the behavior of both compensation topologies when they are detuned due to the tolerances of their components. To compare their performances, a Monte-Carlo analysis was carried out using Simulink and MATLAB. The tolerance values, assigned independently to each component, fall within a [ − 20 , 20] % range according to a normal distribution. Histograms and scatter plots were used for comparison purposes. The analysis reveals that the LCC network allows a tighter control over the currents that flow through the magnetic coupler coils. Moreover, it was found that the increments in those currents can be limited to some extent by selecting capacitors featuring low tolerance values in the LCC compensation. Nevertheless, the SS network remains an appropriate choice if size and cost are essential constraints in a given design.

The electrical faults on transmission lines are detected and isolated by the system protective devices.Transmission lines with series compensators require more attention and special protection settings. Once the fault hasbeen cleared, outage times can be reduced. This paper demonstrates the usage of artificial neural network (ANN) forextra high voltage (EHV) series compensated transmission line fault location. The results show that the proposed ANNis promising and very accurate for fault location estimation. Furthermore, the ANN for the compensated line by onethree-phase bank has been presented. In addition, a new fault detection and location method have been extensivelytested using MATLAB software for a 400-kV, 300-km transmission line. The results demonstrated a high accuracy androbustness of the ANN-based algorithm. Fault detection, types, locations, path resistances and the fault inception anglesare studied. The different power system data currents, voltages, capacitances, angles and time constants of the sourcesare covered. Experimental results were provided to confirm the theoretical results which coincided perfectly together.The results of the present work were complied and clarified with other works.

Abstract Emerging subsynchronous oscillation (SSO) issues in grid-connected wind farms have gained serious attention after several incidents occurred in the US and China. The temporal and spatial variation of wind speed, the diversified converter control structures, and the continuously varying number of in-service wind turbine generators (WTGs) greatly affect the equivalent impedance reflected by the wind farms. Such frequency-dependent equivalent impedance, as indicated by both theoretical analyses and practical experiences, has a huge impact on the mechanism and characteristics of SSO. In this regard, WTGs contribute to a more complicated type of SSO than those in conventional turbo-generators (CTGs). For instance, SSO in practical wind power systems can be triggered without the participation of series compensation in the transmission network. The emerging SSO phenomena observed in practical WTGs are relatively new, and cannot be properly interpreted by existing literature. This work will first review the historical development of SSO definitions and classification by IEEE, followed by discussions on recent incidents in practical wind farms due to the emerging SSO. Subsequently, new terminologies and classification of SSO are proposed with the aim to better understand SSO in large-scale wind integrated power systems. This paper offers a practical insight and a future perspective for the reader to properly deal with SSO associated with wind power systems. Highlights • WTGs associated SSO is different from that of conventional CTGs. • The frequency of WTG-associated SSO is greatly influenced by wind speed, series compensation, WTC controls and parameters. • The SSO mechanism in wind farms is difficult to explain with existing IEEE classification. • New classification of SSO is proposed in which it's classified into torsional, L-C and converter-grid oscillation. [ABSTRACT FROM AUTHOR]

Power Capacitors plays a vital role in reactive power compensation. When the capacitors are connected to the transmission line, it improves the reactive power. Although the reactive power is improved, there is a possibility for sub synchronous resonance created by this capacitors in the transmission line can travel to the generator side. The sub synchronous resonance causes electro-mechanical stress in the generator shaft which ultimately leads to malfunction of the entire system. It is necessary to find out operating modes of the generator and turbine when the line is compensated with capacitors. Once the operating modes are clear, torsion analysis will give the weak points in the turbine generator shaft which is encountered immediately when sub synchronous resonance arises. It is possible to damp the sub synchronous resonance when the weak points are monitored continuously. In this paper, three phase generator is coupled with a prime mover and the line is compensated with the series capacitors. The stress on the turbine is analyzed based on the torque of two rotating machines. Finite element method gives the weak points in the turbine generator shaft system. [ABSTRACT FROM AUTHOR]

Infrastructure reinforcement using high-voltage direct-current (HVDC) links and series compensation has been proposed to boost the power transmission capacity of existing ac grids. However, deployment of series capacitors may lead to subsynchronous resonance (SSR). Besides providing bulk power transfer, voltage source converter (VSC)-based HVDC links can be effectively used to damp SSR. To this end, this paper presents a method for the real-time estimation of the subsynchronous frequency component present in series-compensated transmission lines—key information required for the optimal design of damping controllers. A state-space representation has been formulated and an eigenvalue analysis has been performed to evaluate the impact of a VSC-HVDC link on the torsional modes of nearby connected thermal generation plants. Furthermore, the series-compensated system has been implemented in a real-time digital simulator and connected to a VSC-HVDC scaled-down test-rig to perform hardware-in-the-loop tests. The efficacy and operational performance of the ac/dc network while providing SSR damping is tested through a series of experiments. The proposed estimation and damping method shows a good performance both in time-domain simulations and laboratory experiments. [ABSTRACT FROM AUTHOR]

A dynamic voltage restorer (DVR) can be installed in a middle-voltage (MV) power grid, to concurrently protect a cluster of sensitive loads from voltage sags. To further improve its efficiency and reduce the difficulty in its implementation, a novel control strategy for operating such a DVR as a virtual impedance in series with sensitive loads is proposed in this paper. In addition to its usual function of compensating for voltage sags, such a DVR can also operate as a virtual inductance, to function as a fault current limiter (FCL) during a downstream fault, or a virtual capacitance, to function as a series compensator (SC) to compensate the voltage loss along the feeder line during heavy load. Based on a dual-loop control design, strategies for operating a DVR as a series virtual inductance and a virtual capacitance are proposed, and methods for tuning the parameter values and a stability analysis of the whole system are presented. The feasibility and effectiveness of the proposed method are verified by simulations using the PSCAD software, and experimental results obtained using a prototype DVR are presented. [ABSTRACT FROM AUTHOR]

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This paper investigates the modal repulsion happened in the sub-synchronous resonance between a synchronous generator and series-compensated transmission line. The investigation is based on the closed-loop model of the series-compensated power system consisted of the torsional and electrical open-loop subsystems. Analytical explanation is presented to show how the SSO modal repulsion is formed as the result of moving close and apart between two open-loop SSO modes. Analysis is carried out to indicate that the peak of the SSO modal repulsion occurs when the two open-loop SSO modes from the torsional and electrical subsystem are closest to each other on the complex plane, which is referred to as the open-loop modal coupling. Estimation on the peak, i.e., the maximum damping degradation of the SSO modes, is derived in the paper. Subsequently, a method of open-loop modal analysis is proposed. Applications of the proposed method of open-loop modal analysis to study the SSOs caused by the DFIGs under the condition of the modal repulsion in the power system are demonstrated and evaluated by example power systems. The concept of modal repulsion explains why the grid connection of the DFIGs may bring about the SSO instability risk in the power system. [ABSTRACT FROM AUTHOR]

To install a new infrastructure of a power transmission line is not only costly but also time-consuming, and it also have some harmful impact on our environment and therefore existing transmission infrastructure is important to use effectively. FACTS is a popular solution to utilize this existing power transmission system by using series compensation by means of the series capacitor to enhance the power transmission capacity as well as voltage stability. This paper explores the utilization of series capacitor applying to the power grid of Eastern part of Bangladesh. For doing this we have considered the analytical calculation of 10% to 85% compensation of that power line. As a result, we have observed that the power transfer capacity has been enhanced about 37 times and it also improve the voltage stability, when the compensation ration is 85%. We consider our calculation mathematically and represent the load curve and voltage profile by plotting in Matlab. [ABSTRACT FROM AUTHOR]

This paper proposes an H ∞ damping controller for the doubly-fed induction generator (DFIG) based wind farm (WF) to mitigate sub-synchronous control interactions (SSCI) with series capacitor compensated lines. A multi-input multi-output (MIMO) uncertain state-space model is developed to reflect the main SSCI characteristics considering the uncertainties of wind speed, series compensation (SC) levels and system parameters. The SSCI is analyzed using the eigenvalue analysis of the uncertain system model. In order to damp the SSCI between the WF and series capacitor compensated lines under uncertainties, an H ∞ damping controller is designed for the rotor side converter (RSC). The weighting functions are designed to meet the mitigation requirements of sub-synchronous oscillation currents and output power. The robust stability (RS) and robust performance (RP) of the system are validated by the µ analysis. The performance of the H ∞ damping controller is demonstrated by time domain simulations of a 90 MW wind farm model with different wind speed, and SC levels. The case study with 6 m/s wind speed and 70% SC level shows superior performance of the H ∞ damping controller. [ABSTRACT FROM AUTHOR]

Subsynchronous resonance (SSR) is a phenomenon in which electrical energy is exchanged between generators and transmission systems below power frequency. It happens due to interaction of a series compensated transmission line with a generator. It results in oscillation in the shaft and power swing. In addition, SSR causes increased magnitudes of voltage and current consequently occurrence of ferroresonance. It is obviously clear that protective relays are affected in such conditions. SSR can be damped by several methods; however, protective relays must be adaptive to prevent mal operation independently. In this paper, Manitoba Hydro electrical network with series capacitor is simulated by PSCAD/EMTDC. The impact of SSR and ferroresonance on operation of overcurrent relay is analyzed. An adaptive algorithm based on subharmonic measurement and ferroresonance analysis in time domain is proposed for overcurrent relay. The algorithm detects SSR and ferroresonance, and changes setting values of the relay to prevent mal operation. Furthermore, it distinguishes protection of the hydro generator against subharmonics, which interact with natural frequencies of the rotor. Finally, the algorithm is examined in SSR condition to certify the correct operation. [ABSTRACT FROM PUBLISHER]

This paper proposes a novel damping controller for subsynchronous resonance (SSR) mitigation using existing 11-kV variable frequency drive interfaced auxiliary power plant loads. The input of the proposed auxiliary damping controller is the turbine output power (Pt) . This is a standard signal that is monitored in power plant control rooms and is available locally without the need for additional measurement and/or communication infrastructure. The auxiliary damping controller (ADC) adds an auxiliary speed signal to the existing speed reference in the closed-loop motor drive control in response to any torsional range oscillations seen in Pt, via a feedback compensator. The ADC extracts damping by exploiting SSR load interactions and is tuned using a residue-based pole placement technique. The ADC performance is evaluated for both torsional interaction and torque amplification types of SSR in the IEEE First Benchmark and IEEE 68-bus networks. The results show that the ADC is effective in providing positive damping to mitigate unstable SSR oscillations under a range of operating conditions. The proposed solution is a simple yet effective means of providing local control of SSR with minimal additional cost. [ABSTRACT FROM PUBLISHER]

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]

To install a new infrastructure of a power transmission line is not only costly but also time-consuming, and it also have some harmful impact on our environment and therefore existing transmission infrastructure is important to use effectively. FACTS is a popular solution to utilize this existing power transmission system by using series compensation by means of the series capacitor to enhance the power transmission capacity as well as voltage stability. This paper explores the utilization of series capacitor applying to the power grid of Eastern part of Bangladesh. For doing this we have considered the analytical calculation of 10% to 85% compensation of that power line. As a result, we have observed that the power transfer capacity has been enhanced about 37 times and it also improve the voltage stability, when the compensation ration is 85%. We consider our calculation mathematically and represent the load curve and voltage profile by plotting in Matlab. [ABSTRACT FROM AUTHOR]

• A PV farm installed close to a wind farm is shown to effectively damp SSO. • Reactance crossover and the Nyquist criterion are used to analyze the risk of SSO. • Instabilities predicted by the two methods are validated with EMT simulations. • Both methods are able to predict SSO. • The Nyquist criterion performs better regarding estimating oscillation frequencies. As more power electronics are introduced into the power system, its stability is impacted, e.g., through undesired interactions. One such interaction is called sub-synchronous control interaction (SSCI), an example being an interaction between a DFIG wind farm and a series compensated line. In this paper, two methods are used to assess the risk of SSCI: the reactance crossover method, and the Nyquist criterion. The analysis is performed on three case studies: one system based on the IEEE First Benchmark System, and the other system is modelled as a typical Swedish transmission system with two different degrees of series compensation. Both methods predict SSCI in all three case studies, with the Nyquist criterion being able to predict the oscillation frequency more accurately. To mitigate the sub-synchronous oscillations, a PV farm is implemented and placed in parallel to the wind farm. The performed simulations show that it is able to damp the oscillations successfully in all case studies. [ABSTRACT FROM AUTHOR]

The integration of system compensation such as Series Compensator (SC) into the transmission line makes the coordination of directional overcurrent in a practical power system important and complex. This article presents an efficient variant of Particle Swarm Optimization (PSO) algorithm based on Time-Varying Acceleration Coefficients (PSO-TVAC) for optimal coordination of directional overcurrent relays (DOCRs) considering the integration of series compensation. Simulation results are compared to other methods to confirm the efficiency of the proposed variant PSO in solving the optimal coordination of directional overcurrent relay in the presence of series compensation.

Locating a fault in a series-capacitor-compensated transmission line (SCCTL) is a challenging task due to the action of a metal-oxide varistor a nonlinear element present as a part of the protection system of the series capacitor. In this paper, an accurate fault-location algorithm that uses synchronized measurements from both ends of the SCCTL is presented which provides fault-location results without using the model of MOV or natural fault loop for single-phase-to-ground, and double-phase-to-ground faults. Another salient feature of the proposed technique is that the subroutines for locating faults in different sections transmission line yield almost identical fault-location results regardless of which section the transmission line is faulted. The proposed technique could also be extended to the double-circuit transmission lines. First, the proposed technique is introduced and its features are elaborated through detailed mathematical analysis. Thereafter, a 500-\textkV system with an SCCTL is designed in PSCAD, while the fault-location algorithm is modeled in MATLAB. The proposed algorithm is tested through simulations covering various fault scenarios in an SCCTL. For performance evaluation, the comparative analysis of the proposed technique with a well-known existing technique is performed in this paper. [ABSTRACT FROM PUBLISHER]

The wind speed of high uncertainty has an important impact on the emerging subsynchronous resonance (SSR) caused by the interaction between doubly-fed induction generator (DFIG)-based wind farms and series-compensated transmissions. This paper proposes a piecewise probabilistic collocation method (PPCM) for assessing the probabilistic stability of SSR in terms of the random wind speed. The PPCM can tackle the inherent nonlinearity resulting from the switching among different operational modes of DFIG. Using the proposed PPCM, the more accurate probability density function (PDF) of the damping can be obtained with a small computation burden. Furthermore, for the probabilistic stability assessment of SSR, this paper also develops the Weibull probabilistic model of the wind speed using the two-year statistical data. The results obtained with the proposed method show consistence with those of the Monte Carlo method (MCM). Finally, field data of SSR events in the practical wind farms are also presented to validate the effectiveness of the proposed method and its produced results. [ABSTRACT FROM PUBLISHER]

A new two-terminal fault-location algorithm for series-compensated double-circuit transmission lines based on the distributed parameter line model is proposed. The system is considered as fully transposed, and a six-sequence component network is introduced to decouple the mutual electromagnetic effects between circuits. Two subroutines designated for the fault that occurs on the left or right side of the series compensator are developed. In each subroutine, the voltage of the series-compensated device is eliminated based on the fact that the sequence voltages calculated from two sides are equal at the fault point. The fault-location function is constructed by utilizing the feature in which the transition resistance is purely resistant at the fault point. The proposed algorithm does not rely on the equivalent model of a series-compensated device. Moreover, it does not require the fault type to be known, and there are no fault-location identification and pseudoroot elimination problems. PSCAD is employed to generate numerous fault cases in diverse conditions and the high accuracy of the proposed fault-location algorithm is validated in MATLAB. [ABSTRACT FROM AUTHOR]

Solar based renewable power generation is more important to compensate fossil fuel power generation. It is necessary to implement Maximum Power Point Tracking (MPPT) system to reduce cost of PV array system by decreasing the number of solar panel required to generate the power. Since the solar power fluctuates with the sunlight's intensity, it requires conversion to maintain the desired voltage like inverters. In this paper, a series compensation scheme is suggested. Perturbation and observation (P&O) algorithm of MPPT. A single stage architecture of photovoltaic generators which is used for residential applications are incapable to boost the voltage of the PV modules and also provides deficient input voltage range in spite of providing deplete power loss. This research work proposes a series connection of buck-boost converter which operates only in buck mode and also processes a fraction of the power input from the inverter while operating at high efficiency. This inverter focused SPWM pulses and produces pure sine wave as output. The duty ratio is decreased to less than 0.5 hence switching losses also reduced. The proposed logic is carried out in simulation and hardware setup of 480W prototype and the results were analyzed to enhance the advantage of the series compensation approach. [ABSTRACT FROM AUTHOR]

This paper reports the use of a novel ultra-high speed scheme to release the distance relay to operate for a fault during a power swing in the series compensated line. In the scheme, in order to extract the fault induced voltage and current components, voltage and current samples are analyzed by the multi-resolution morphological gradient (MMG), first. Then, the fault initiated forward travelling wave is computed at the distance relay point. Next, Likelihood ratio [LR] test is utilized to detect a jump in the statistical mean of the calculated forward travelling wave. Finally, a support vector machine (SVM) classifier is employed to distinguish faults from other normal capacitor and switching transients. It is shown that in all of the simulated cases, our ultra-high speed algorithm was successful in fault detection across a wide range conditions including, fault type, fault resistance, fault location, pre-fault loading and fault inception time. Moreover, we found that using the proposed scheme significantly speeded the fault detection, in comparison with the existing phasor based methods. In addition, the improvements noted in our algorithm are achieved with a low computational burden. [ABSTRACT FROM AUTHOR]

In a transmission network, autoreclosing provides quick restoration of the line for transient faults and improves system stability. Autoreclosing during permanent fault may damage power system elements. This paper presents a method to block autoreclosing for permanent line-to-ground faults on multicircuit series compensated transmission line using synchronized measurements from both ends. The method utilizes measurements from the healthy phases of the line to calculate an index, which determines the persistence of a fault to control the reclosing. In the case of a transient line-to-ground fault, the index is high during the fault and zero after extinction of the secondary arc. The index can be used to modify the dead time of the recloser and thereby reclosing during fault (both transient and permanent) is prevented. The proposed method is tested using the sample data obtained from EMTDC/PSCAD simulation of an actual series compensated line in the Indian power grid. Results demonstrate the accuracy of the proposed method. [ABSTRACT FROM PUBLISHER]

In this paper, based on the theory of traveling waves, the fault distances on long transmission lines with various series-compensation levels are determined using transient current and voltage frequencies. Transmission lines with series compensation are modeled using Alternative Transients Program software with frequency-dependent effects on the line included in the simulation. The transient current and voltage signals are obtained from the model. A fast Fourier transform is used for frequency-domain conversion and fault location is estimated from the frequencies of fault-generated harmonics in the transient spectrum. The algorithm is implemented in MATLAB. To investigate the effect of compensation on accuracy, the results are obtained for different series-compensation levels. The undesirable source-inductance effect is removed and estimation accuracy is further improved using a waveform-relaxation method. The method is found to be successful in determining fault location on series-compensated transmission lines. The effects of the compensation level, fault resistance, and phase angle are investigated. [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]

The problems of asynchronous self-excitation of a synchronous machine with two windings on the rotor and a series capacitance in the circuit have been considered. A formula for calculating free oscillations has been given. It has been shown that, for a system consisting of a symmetric synchronous machine and a series capacitance, there are two natural frequencies, each corresponding to a certain zone of self-excitation. The equation of the curve that describes the region of self-excitation has been obtained. The effects of different parameters of machine on the lower part of the self-excitation zone have been investigated. It has been shown that this part of the zone is determined by the ratio between the active resistances of the machine circuits, but not their absolute values. A method to determine parameters providing the required compensation of the machine reactance has been given. [ABSTRACT FROM AUTHOR]

This paper presents a novel control of a large-scale PV solar farm as STATCOM, termed PV-STATCOM, for alleviation of subsynchronous resonance (SSR) in a steam turbine driven synchronous generator connected to a series compensated transmission line. During nighttime, the PV solar farm can operate as a STATCOM with its entire inverter capacity for SSR mitigation. During daytime, if a system fault triggers SSR, the solar farm autonomously discontinues its normal active power generation and releases its entire inverter capacity to operate as PV-STATCOM for SSR prevention. Once the subsynchronous resonances are damped, the solar farm returns to its normal real power production. Electromagnetic transients studies using EMTDC/PSCAD are performed to demonstrate that a solar farm connected at the terminals of synchronous generator in the IEEE First SSR Benchmark system can damp all the four torsional modes at all the four critical levels of series compensation, and return to normal PV power production in less than half a minute. This proposed PV-STATCOM technology can either obviate or reduce the need of an expensive flexible ac transmission system device to accomplish the same objective. Furthermore, this technology is more than an order of magnitude cheaper than a conventional static var compensators or STATCOM of similar size. [ABSTRACT FROM PUBLISHER]

The emerging subsynchronous resonance (SSR) caused by the interaction of wind turbine generators (WTGs) with series compensation has aroused great concerns. For this particular issue, this paper is aimed to fill the gap between theoretical studies and actual observations. By analyzing the field data of 58 SSR events captured in a practical wind power system and examining the observed dynamics with previous theoretical results, the mechanism and characteristics of SSR are revealed in a more explicit and substantial way. The necessary conditions and dominant influential factors are identified and the underlying reasons are discovered. Theoretically derived as well as practically measured impedance models have demonstrated that the converter control of doubly fed induction generator (DFIG) produces negative resistance at the slip frequency and thus causes unstable SSR; while permanent magnet synchronous generators and self-excited induction generators are just passively engaged in those SSR incidents. The distribution of the oscillation frequency has also been examined with field measurements. It is discovered that WTGs at different locations participate into the same SSR mode and their frequencies are not fixed but keep changing with the time, the variation of grid topology, and the number of online generators. [ABSTRACT FROM PUBLISHER]

Protection of series compensated line is a challenging task due to non linearity involved in presence of series capacitance. The novelty of this research paper is the application of capacitor voltage drop signals of fixed series capacitors (FSC) over one cycle after occurrence of fault for faulted phase classification and to the fuzzy system for fault distance estimation in a 400 kV transmission line with FSC. Such application of capacitor voltage drop signals has never been implemented in any fault analysis schemes which makes this technique novel. Feasibility and reliability of the proposed technique has been tested for all ten types of shunt faults on power system model at different fault inception angles (FIA), realistic fault resistances over a range of fault locations. The proposed fuzzy logic based technique has less computation complexity. Real transmission system parameters of 400 kV Wardha - Aurangabad transmission line, India (400 km) with 40% compensation at one end are implemented for this research. Percent absolute error is calculated for performance evaluation of the proposed method. Large numbers of test cases are generated which provide complete distance protection scheme giving quite accurate results with percent absolute errors mostly within 2.75% demonstrating more accuracy as compared to previous fuzzy based fault location schemes, least complexity and robustness of the proposed technique. [ABSTRACT FROM AUTHOR]

This paper proposes a modified pq-theory-based control of a solar photovoltaic (PV)-array-integrated unified power quality conditioner (PV-UPQC-S). The system incorporates clean energy generation along with power quality improvement, thus increasing functionality of the system. The fundamental-frequency positive-sequence components of voltages at the point of common coupling (PCC) are extracted using the generalized cascaded delay signal cancellation technique, which are then used in pq-theory-based control to estimate reference signals for the PV-UPQC-S. This modification in pq theory enables its application for PV-UPQC-S control under conditions of distorted PCC voltages. The series voltage-source converter (VSC) of the PV-UPQC-S operates such that it shares a part of the reactive power of the load even under nominal grid conditions. This increases the utilization of the series VSC while reducing the rating of shunt VSC. The PV array is integrated at the dc bus of the UPQC and provides a part of active load power, thus reducing demand on the supply system. The dynamic performance of the modified pq-theory-based PV-UPQC-S is verified by simulating the system in MATLAB-Simulink with a combination of linear and nonlinear loads. The steady-state and dynamic performances of the system are then experimentally validated through extensive testing on a scaled-down laboratory prototype. [ABSTRACT FROM AUTHOR]

The paper presents a novel idea of protection of the multi-terminal Extra High Voltage (EHV) transmission line having multiple Series compensation. A statistical learning perspective for improved classification of faults using Artificial Neural Networks (ANN) has been proposed. The protective scheme uses single end cur-rent data of three phases of line to detect and classify faults. A Multiresolution Analysis (MRA) wavelet transform is employed to decompose the signals acquired and further processed to extract statistical features. The statistical features learning algorithm utilizes a set of ANN structures with a different combination of Neural Network parameters to determine the best ANN topology for Classifier. The algorithm generates different fault patterns arising out of different fault scenarios and altering system parameters in the test system. The features are selected based on ANOVA F-test statistics to determine relevance and improve classification accuracy. The features thus selected from fault patterns are given to the Hybrid Wavelet-ANN structure. The ANN once trained on a part of data set is later tested on the other part of unseen patterns and further validated on rest of the patterns. To provide a comparative Support Vector Machine Classifier is used to classify the fault patterns. A 5 fold cross validation is used on the data set to check the accuracy of SVM. It is shown that the proposed method using Pattern Recognition using Hybrid structure provides a high accuracy with reliability in identifying and classifying fault patterns as opposed to SVM. [ABSTRACT FROM AUTHOR]

This paper presents a non-unit protection scheme for series capacitor compensated transmission lines (SCCTL) using discrete wavelet transform and k-nearest neighbor (k-NN) algorithm. All the protective relaying functions such as fault detection, fault classification, faulty phase identification and fault location estimation have been considered in this work. Such a comprehensive work providing all protective relaying functions for protection of double circuit SCCTL utilizing k-NN has not been reported so far. The signal processing and feature extraction are done using discrete wavelet transform due to its capability to differentiate between high and low frequency transient components. For fault detection and classification, only approximate wavelet coefficient of current signal up to level 1 has been used; while for k-NN location estimation, both voltage and current signals of the two circuits are decomposed up to level 3 have been used. Finally, the standard deviation of one cycle pre-fault and one cycle post-fault samples of the approximate wavelet coefficients are calculated to form the feature vector for the k-NN-based algorithm. The performance of the proposed technique is evaluated for large number of fault events with variation in fault type including inter-circuit faults, fault inception angle, fault location and fault resistance. The change in position of series capacitor and different degree of compensation has been discussed. The accuracy of the proposed k-NN-based fault detection and classification module is 100% for all the tested fault cases with a decision period of less than half cycle. The k-NN-based fault location scheme estimates the location of fault with ≤1% error for most of the tested fault cases, which is an exceptional attribute of the proposed scheme as compared with 10–15% error of conventional distance relaying scheme. [ABSTRACT FROM AUTHOR]

The objective of this paper is to evaluate the impact on the operation of conventional three-stepped distance relaying schemes for protecting the series compensation transmission line and to analysis the effects series compensation on different carrier aided transfer trip scheme under different fault condition. The presence of series compensation in transmission creates over-reaching issues in distance relay due to the net fault impedance of transmission line reduce. Analytical studies of such situation are simulated by using PSCAD and analyzed various responses of distance relays for different fault and system conditions. An enhanced distance protection scheme is implemented to eliminates issues on distance relay for series compensated line. It is also simulated the auto-recloser schemes to discriminating between the temporary and permanent fault. [ABSTRACT FROM AUTHOR]

Inductively coupled power transfer (ICPT) systems, which are superior to batteries due to their real-time power supplycapacity have been used in mooring buoys for the purpose of long-term measurements. A multiple-receiver ICPT system for mooring buoys, which contains a mooring cable for transmitting power, is proposed in this paper to obtain the corresponding profile parameters. Series compensation is applied to all three sections, including the transmitter, the mooring cable and multiple receivers. The voltage of an underwater system with arbitrary load can be stabilized. On that basis, high efficiency can be obtained. By adopting Wolfram Mathematica a detailed analysis of both double-receiver and multiple-receiver ICPT systems for mooring buoys is presented. Finally, a prototype ICPT system with three receivers mounted on a 30 m mooring cable was built to verify the theoretical analysis. Experimental results show that the power transfer efficiency exceeds 45%. Both theoretical analysis and experiments indicate that this system is appropriate for measuring ocean profile parameters. [ABSTRACT FROM AUTHOR]

The aim of the article is to present an analysis which has dealt with the effect of series compensation on the optimal position of a series-shunt connected FACTS device of a transmission line. TheFACTS device has been used in a line model called ‘actual transmission line model’. The transmission line was long and had a series compensation at the center. A Matlab based simulation had been used to investigate the effect of series compensation of thetransmission line on the optimal location of a seriesshunt FACTS device and finally, the optimal position of the series-shunt FACTS device was identified. The result of the study revealed that with the change of the level of series compensation values (Zc) the optimalposition of a series-shunt facts device was changed. The results of this work were very useful in optimizing the location of various series-shunt FACTS devices in order to acquire an efficient long transmission line. Therefore, a cost effective and efficient installation of FACTS devices by diverting the optimal location ofFACTS device near the substation was also achievable by this simulation.

One challenge in power-system control designs is the gap between numerical model-based analysis and complex real-world power systems. With increased data and measurements being collected from power systems, data-driven analysis (e.g., machine learning) may provide an alternative approach to reveal hidden information through learning from the real system data, and provide insights for better control scheme design during the utility planning process. In this study, data-driven feature analysis is performed to evaluate the relationships between series compensation, power generation, and path flows in a real transmission system, as well as temporal patterns. The main data-driven analysis methods, including statistical cross correlation, multinomial logistical regression, and classification and regression trees, are integrated for feature selection and developing predictive models of series compensation. Analysis results demonstrates the effectiveness of the proposed methodology in feature analysis and the potential to help improve power-system control scheme design. [ABSTRACT FROM AUTHOR]