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Currently there is a need to synchronize operation of the electric power system in the remote areas and increase of existing lines transmission capacity. The construction of new power transmission lines involves high economic expenditures. Well-known papers consider the issues of application of controlled series compensation devices only for long-distance power transmission lines with voltage of 500 kV and higher to increase the transmission capacity and the level of stability. The aim of the study is to increase the stability and the limit of the transmitted power when controlled series compensation devices are installed on 220 kV lines. It is necessary to develop a criterion of aperiodic steady-state stability of an electric power system with a 220 kV-controlled power transmission line. Methods of mathematical modeling of electric power system, the theory of long-distance power transmission lines and electromechanical transients, and methods of analyzing electric power system stability were used. A.M. Lyapunov’s first approximation method was used to develop a simplified mathematical model. We applied the developed software as a simulation tool. An analysis was carried out to study the influence of series compensation devices regulation coefficients on the aperiodic steady-state stability of the electric power system and the transmission capacity of 220 kV power transmission lines. A change in the modulus of voltage drop at the power transmission and the angle characteristics under the influence of the regulation coefficients of the series compensation device was revealed. A criterion of aperiodic steady-state stability has been developed for systems of this kind with controlled series compensation. It differs from traditional ones by considering the changes in the voltage drop in the power transmission and it allows more accurate estimation of the proximity to the stability threshold. An assessment of aperiodic steady-state stability according to the formulated criterion for an electric power system with a controlled series compensation device on a 220 kV line was obtained. The values of the control coefficients of the series compensation device have been determined. No violation of the steady-state stability occurs under the given values. The results can be used to solve the issues of increasing the transmission capacity of transmission lines to improve the stability of the system.

This paper deals with the design of SPM vernier machine with high slots/pole/phase q, to get higher torque density as well as improved power factor by applying the concept of series compensation. The torque density of a vernier machine can be enhanced by increasing the number of slots/pole/phase q, but as q increases the drastic increase in the reactance makes the power factor even worse. Therefore, it is general to choose low q, even if higher torque can be obtained with higher q. In this study, the idea of series compensation is applied to get vernier machine with high q without the low power factor problem. Series compensation is performed by supplying the desired reactive power to the machine from an additional inverter with a floating capacitor. To validate the theoretical analyses, three SPM vernier machines with different q (1 ∼ 3) are designed and then analyzed by using FEM.

Although there currently exists a wide range of voltage regulators that are commercially available, the search for devices with a simpler physical design remains the focus of research studies. Following this line, an electromagnetic voltage regulator (EVR) arrangement has been proposed. The EVR is constituted of an autotransformer that supplies, via discrete taps, a series transformer that injects voltage for regulating the feeder voltage. Even though its operating principle is shown as being similar to that of other devices on the market, the physical arrangement and operating strategy of EVR show novelties which result in properties such as: economic attractiveness, constructive simplicity, and operational reliability. Moreover, when installing voltage regulators, efficacy studies must be carried out to optimize equipment design. In this context, this paper aims at evaluating the factors that influence the effectiveness of the EVR in restoring voltage variations according to the determinations imposed by regulatory agencies. The ultimate goal of this study is to determine the voltage deviation range that the EVR is able to restore. To achieve this goal, a mathematical modeling of the EVR is given and study cases are computationally carried out to investigate its performance when connected to a typical distribution feeder.

—Subsynchronous resonance (SSR) is an undesirable phenomenon in series compensated power system which tries to menace the stability of both electrical and mechanical system. This paper researches t...

To improve transmission capacity and stability margin of the power system, the doubly fed induction generators (DFIGs) based wind farm is transmitted over lines equipped with series compensation (fixed capacitors). However, the utilisation of series compensation brings the potential risk of subsynchronous resonance (SSR) in the power system. In this study, the SSR issue in DFIGs based wind farm integrated to a series-compensated network is studied based on the eigenvalue analysis and equivalent impedance model. The linearised state-space model of DFIGs based wind farm integrated to a series-compensated network is built first. Participation factors, sensitivities of eigenvalues and root loci, obtained by linearised state-space model, are observed to investigate the mechanism and the key parameters of SSR. Then, a method that can mitigate SSR in DFIGs based wind farm integrated to a series-compensated network is proposed based on virtual series resistance of the rotor. At last, the eigenvalue analysis and simulation are conducted to verify the effectiveness of the proposed mitigation method.

There are significant concerns regarding the stability of increased wind power generation in weak power grids. This paper investigates and improves the stability of Wind Turbine Squirrel Cage Induction Generators (WT-SCIGs) with series compensation and weak interconnections to the power grid. Detailed time-domain and state-space modeling have revealed new bifurcations and oscillatory modes for a WT-SCIG connected radially to a weak grid through a series compensated line. The stability domain analyses are carried out by computing bifurcations in the system by analyzing eigenvalues of the linearized system. The analyses demonstrate for the first time how the degree of compensation at which the Hopf bifurcation occurs depends on the X/R ratio of the line, operating slip of the induction generator, and voltage regulator parameters as well as the time delays in measurements. A new damping controller is proposed, which greatly improves the dynamic stability of the WT-SCIG and eliminates destructive Hopf bifurcations in weak grids for a wide range of series compensation. This allows for a much larger percentage of series compensation than what is usually possible, while avoiding instabilities, thereby maximizing the power transfer capability.

With the rapid development of new energy, the problem of power oscillation caused by large-scale wind farm access system has become increasingly prominent, such as the subsynchronous resonance between doubly-fed induction generator (DFIG) and fixed series compensation, which threatening the security and stability of the system seriously. Since there may not be a single type of wind turbine in the same wind farm, this paper aims to clarify whether there is interaction between different types of wind turbines in the wind farm, thus focuses on the subsynchronous oscillation (SSO) of a system that including DFIG based wind farm, direct-drive permanent magnet synchronous generator (PMSG) based wind farm and fixed series compensation. A linearization model of hybrid-based wind farm is established to analyze the influence of wind farm proportion, control parameters on the operation stability of the system. Based on the dynamic impedance model of hybrid-based wind farm, the mechanism of SSO is further revealed. A time-domain simulation model is built in EMTDC / PSCAD to verify the correctness and effectiveness of the theoretical analysis.

Integration of wind energy resources into the grid creates several challenges for power system dynamics. More specifically, Type-3 wind turbines are susceptible to subsynchronous control interactions (SSCIs) when they become radially connected to a series-compensated transmission line. SSCIs can cause disruptions in power generation and can result in significant damage to wind farm (WF) components and equipment. This paper proposes an approach to mitigate SSCIs using an online frequency scan, with optimized phase angles of voltage harmonic injection to maintain steady-state operation, to modify the controllers or the operating conditions of the wind turbine. The proposed strategy is simulated in PSCAD/EMTDC software on the IEEE second benchmark model for subsynchronous resonance. Simulation results demonstrate the effectiveness of this strategy by ensuring oscillations do not grow. Published version

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.

Sub-synchronous oscillations (SSOs) in doubly-fed induction generator (DFIG)-based series compensated power systems are mainly caused by sub-synchronous control interaction (SSCI). SSCI is the most recently found type of sub-synchronous resonances. In this article, SSCI is elaborated and investigated by performing eigenvalue analysis on a mathematically modeled DFIG system. The occurrence of SSCI is observed and the results of eigenvalue analysis are validated through a down-scaled 7.5-kW experimental setup of a grid-connected DFIG. Based on the analysis, the proportional control parameters of the rotor-side converter (RSC) are found to be very sensitive towards the sub-synchronous modes of the system. The results obtained from both the simulation and the experimental analysis show that if the sensitive proportional parameters of the RSC are tuned properly, then the DFIG system can become immune to the SSCI for any level of series compensation.

TL (Transmission Line) congestion is a key factor that affects the power system operational cost. In addition of renewable generation in National Grid of Pakistan, transmission line congestion are frequent. Consequently, the network in this particular region faces severe congestion and dynamic stability problems. It has been planned that renewable plants shaved to curtail some available generation to minimize this inevitable congestion. However, one of the cost-efficient solutions to this problem is series compensation of lines using TCSC (Thyristor Controlled Series Compensation). It significantly increases the transfer capability of existing power transmission and enhances the dynamic stability of system at a lower cost, and has shorter installation time as compared to the construction of new TLs. This paper deals with the dynamic modeling of a TCSC in the NTDC (National Transmission and Dispatch Company) network with its applications to alleviate congestion during fault conditions. This study has been carried out using simulation software PSS/E (Power System Simulator for Engineers) which does not have a predefined dynamic model for TCSC, this leads to the necessity of creating a user defined model. The model of TCSC has been programmed in FORTRAN and compiled along with existing dynamic models of network components. The results indicate that power flow and dynamic stability of network is enhanced

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 $(P_{t})$ . 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 $P_{t}$ , 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.

The rise in power electronic devices in power system has increased the problems of harmonics and power quality. In this paper I have discussed about the harmonics that are developed in power system due to non-linear loads. The damage of harmonics may rise from normal level to high level depending on their duration and the order of harmonic .So to mitigate this harmonics in power system I have introduced shunt active power filter by series compensation method. In this paper it is discussed how harmonics are reduced using shunt active power filter and it is shown through MATLAB/Simulink .The results of the simulation have been shown where the harmonics developed in power supply has reduced.

Improvement in the power transfer capability and the system stability of long transmission lines by series compensation is a cost-effective solution. However, the Subsynchronous Resonance (SSR) due to series compensation leads to severe risk of Torsional Interactions (TI). This paper presents, a review on damping of torsional interactions using Voltage Source Converter (VSC) based FACTS with various Subsynchronous Damping Controllers (SSDC) proposed in the literature. This review can help researchers to make a comparative study of the impact of FACTS devices and various subsynchronous damping controllers on damping of subsynchronous oscillations.

Power systems are at risk of sub-synchronous oscillation (SSO) when connecting doubly-fed induction generator (DFIG)-based wind turbines to transmission lines with series compensation. This paper focuses on the mechanism and mitigation strategy of SSO. Firstly, the mechanism of SSO is studied from two aspects: induction generator effect (IGE) and sub-synchronous control interaction (SSCI). An equivalent circuit is developed to illustrate the negative resistance effect. Based on the result of the analysis, the SSO mitigation strategy using notch filter and virtual resistance control is proposed. In order to verify the result of analysis and the effectiveness of mitigation strategy, time-domain simulations are carried out based on PowerFactory DIgSILENT.

FACTS controllers incorporating energy storage device has the ability to operate in all the four quadrants and thereby increases the operational flexibility. In this work, the influence of SSSC supported by Energy Storage (SSSC-ES) on subsynchronous resonance (SSR), in a system provided with fixed series compensation is studied. Effect of SSSC-ES injecting constant real and reactive voltage into the network is analyzed. The sample system is adapted from IEEE FBM and the SSR analysis is carried out using bifurcation technique. Validation of results is done using eigenvalue and transient analysis.

PV and QV curves are signatures of power system operation under different operating conditions and give an important information about the loading of the system and voltage stability. The series and shunt compensation can be utilized to enhance the voltage and flow in the network. In this paper, PV-QV curves have been obtained for a 5-bus test system and are also obtained for IEEE 9-bus system. The impact of the series and shunt and combined series and shunt compensation was simulated and results are compared. The simulation of the system was carried out in Power World simulator. The margin enhancement has been obtained.

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 [ &minus, 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.

In this paper, the battery energy storage supplementary damping control is introduced to suppress the subsynchronous oscillation of DFIG-based wind farm interfaced with series compensation. Firstly, the conventional control strategy of battery energy storage system is analyzed, and the small signal model of doubly-fed wind farm with battery energy storage is established. Then the eigenvalue method is used to analyze the subsynchronous oscillation mode and related participation factors. Based on the above analysis, the supplementary damping control strategy of battery energy storage is designed to suppress the subsynchronous oscillation of DFIG-based wind farm interfaced with series compensation. Finally, the PSCAD electromagnetic transient simulation model is established. The time domain simulation method is used to verify the effectiveness of the proposed control strategy.

In this paper, a supplementary damping control scheme for static synchronous compensator (STATCOM) is proposed to stabilize the oscillation caused by subsynchronous control interactions (SSCI) phenomenon in a series-compensated doubly fed induction generator (DFIG) based wind farm. Various system conditions determine the oscillation frequency, which is usually different for different SSCI events. Therefore, it is a great challenge to design an efficient and reliable damping controller to stabilize the SSCI. A damping controller based on combination of filters, gain, and phase-shifts is designed for STATCOM controller. With the proposed scheme, the STATCOM is able to provide positive damping for a wide range of system conditions, and thus covering a wide band of oscillation frequencies. The performance of the proposed scheme is validated on an aggregated model of an actual wind power system using Simulink environment. The time-domain simulations have demonstrated the effectiveness of the proposed scheme for mitigating the SSCI at various oscillation frequencies.

A new single-input multiple-output (SIMO) converter is proposed in this work by incorporating flyback and buck converters in a master–slave configuration. The objective of this work is to address the cross regulation problem, achieve tight voltage regulation, improve the circuit form factor and attain a fast transient response for a SIMO flyback converter. The flyback converter maintains the output channels within 10% of their rated voltages and the SIMO buck converter is placed in series with the flyback converter such that it compensates for the output voltage deviation. Moreover, a time multiplexing switching scheme decouples output channel to eliminate the cross-regulation problem and remove the need for an additional winding transformer per each output channel. A type II compensator with a peak current mode controller was designed to achieve faster transient response which is critical for the proposed configuration. A thorough steady-state analysis was carried out on a triple output channel topology to obtain the design criteria and component values. MATLAB/Simscape modelling and simulation was used to validate the effectiveness of the proposed converter with the result yielding satisfactory transience even with load disturbance. Additionally, the result of the proposed converter is compared with previously published works.

In the series-compensated grid-connected system (SCGCS), there is an impedance interaction between the inverter impedance and the grid impedance that is prone to cause resonance in the SCGCS. In this paper, firstly, considering the effects of the phase-locked loop (PLL), current-loop, and frequency coupling, the broadband impedance model of the SCGCS is established. The stability of the SCGCS is analyzed by the impedance-based Nyquist stability criterion. It is found from the stability analysis that the impedance interaction between the inverter impedance and the grid impedance is the leading cause of the resonance. An impedance reshaping based resonance suppression method is proposed to suppress the resonance. The phase characteristics of the inverter equivalent output impedance are reshaped from the perspective of impedance. The phase margin at the intersection frequency of the inverter impedance and the grid impedance is improved. The proposed resonance suppression approach mainly consists of reshaping the current loop impedance and the novel phase-locked loop impedance. Finally, simulations and experiments are used to verify the feasibility of the resonance analysis and the effectiveness of the proposed control strategy.

Doubly fed induction generator (DFIG) has become the most widely used type of wind power generation due to its superior technical performance. Series compensation technology is widely used in large-scale and long-distance wind power transmission system because of its high cost performance and significant improvement of transmission capacity. However, it may cause subsynchronous oscillation (SSO). This paper first introduces the definition and harm of subsynchronous oscillation, and then analyzes the advantages and disadvantages of series compensation technology, as well as the mechanism and suppression measures of subsynchronous oscillation of DFIG connected system through series compensation. Through modeling and simulation analysis, the suppression effect of additional subsynchronous damping controller (SSDC) on subsynchronous oscillation of DFIG control system is verified.

As the self-excited induction generator (SEIG) is the most suitable for remote and windy areas, so the pre-evaluation of this generator performance is essential. For better voltage profile and power capability, series compensation can be used. This paper presents an assessment of the shunt, short-shunt and long-shunt compensation configurations. A generalized mathematical model of SEIG is presented. The effectiveness of the generalized mathematical model is then tested on a three-phase, 1.5-kW induction generator operating in all configurations. Proposed Genetic Algorithm (GA) model has been implemented to predict the output power capability and corresponding load voltage for each series compensation under various loading conditions. Results obtained from the proposed (GA) model have been compared with the experimental and simulation results. The comparison confirms the validity and accuracy of the proposed GA model as an assessment tool of induction generator with different compensation configura...

This paper proposes a new fault ride-through (FRT) configuration for a fixed-speed induction generator-based–wind turbine (FSIG–WT). It utilizes a nine-switch converter (NSC) to enable shunt and series compensation in response to the system dynamics and grid faults. The steady-state control strategy and transient-management scheme are developed to ensure proper performance in steady-state, dynamic operation as well as enhanced FRT capability of the FSIG–WT. In addition to that, the developed control strategy tackles the balanced and unbalanced operation of the electric grid with an enhanced positive- and negative-sequence compensation control scheme. The recently reported grid synchronization scheme, namely, the frequency-locked loop (FLL) is implemented to achieve fast phase detection and transient response. Consequently, the performance of the FLL has been compared with the multiple reference–frame–phase-locked loop (MRF–PLL) to demonstrate its superior performance for enhancing transient response. The proposed topology, FLL, and control strategies are verified through a comprehensive simulation study to demonstrate the enhancement of the transient response and FRT capability of FSIG-WT in adherence to grid-code requirements.

In transmission line, the series compensation is used to improve stability and increases the power transmission capacity. It generates sub synchronous resonance (SSR) at turbine-generator shaft due to the interaction between the series compensation and wind turbine system. To solve this, several methods have been presented. However, these provide less performance during contingency period. Therefore, to mitigate the SSR and also to improve the dynamic performance of hybrid wind and PV system connected with series compensated wind farms, the adaptive technique of the Black Widow Optimization algorithm based Fuzzy Logic Controller (BWO-FLC) with UPFC is proposed in this paper. Here, the objective function is solved optimally using BWO technique. Based on this, the Fuzzy Logic Controller is designed. The results proved that the proposed controller performs the mitigation of SSR. The damping ratios of proposed controller to mitigation of SSR are 0.0098, 0.0139, and 0.0195 for wind speed of 6, 8 and 10 m/s respectively.

The processes in distributed series compensation devices in the nonlinear mode of the transformer operation are considered. The analytical expressions for calculation the magnetizing current in the nonlinear mode for the operation of the transformer. The results of the experiment and simulation model of the distributed series compensation device are presented, and the results are compared.

A control strategy is obtained for restraining torsional oscillations owing to SSR over a varying degree of series compensation. A mid-point located SVS equipped with a joint supportive signal composed of line current and voltage deviations has been utilized to damp out torsional oscillations grown due to sub-synchronous resonance. The test system considered for analysis of the usefulness of the controller under consideration is built using IEEE first benchmark model having SVS connected at the mid-point of the transmission line. Eigenvalue analysis has been carried out for the linearized power system model to investigate the unstable torsional modes. To explicate the relative assessment of the system under consideration three secondary controllers are considered. To illustrate the robustness of proposed controller a comprehensive power system model is used which is described by various subsystems, their relations are been described in detail with accuracy. The eigen value analysis illustrates the efficacy of the Combined Line Current and Voltage (CLCV) SVS controller for different percentage of the series compensation as compared to the cases where no controller is used and case where only Line Current SVS controller, Voltage SVS controller are used. All results obtained at various levels of series compensation approves usefulness of the SVS controller under consideration.

Rao S. Thallam Salt River Project 18.1 The Need for Reactive Power Compensation 18-1 Shunt Reactive Power Compensation . Shunt Capacitors 18.2 Application of Shunt Capacitor Banks in Distribution Systems—A Utility Perspective 18-2 18.3 Static VAR Control 18-3 Description of SVC . How Does SVC Work? 18.4 Series Compensation 18-5 18.5 Series Capacitor Bank 18-6 Description of Main Components . Subsynchronous Resonance . Adjustable Series Compensation . Thyristor Controlled Series Compensation . STATic COMpensator 18.6 Defining Terms 18-12

In this paper a comparative study has been performed between combined Thyristor controlled series capacitor (TCSC), Static VAR compensator (SVC) and combined TCSC, Static synchronous compensator (STATCOM) to enhance the steady state, dynamic state and transient state stability of East-West interconnected system (EWIS) of Bangladesh Power System (BPS). Two TCSCs are connected in series with both interconnectors and two SVCs and STATCOMs are connected alternatively in shunt mode at the receiving end of both interconnectors. Steady state, Modal and Transient stability analyses are performed to show the improving effect of series shunt combined compensation on stability and capacity enhancement of EWIS. In case of shunt compensation superiority of STATCOM is also shown in comparison to SVC. In both the cases of comparison series compensation level is kept identical for fair comparison.

In recent years, the technology of wind power developed very rapidly, In order to solve the issue of wind power consumption and improve the utilization of wind power. Large-scale wind power transmission is imperative. Series compensation technology is currently one of the economic and effective measures to solve large-scale wind power transmission. However, after the series compensation, sending wind power will cause sub-synchronous oscillation. In this paper, firstly, the structure and characteristics of three common wind turbines are introduced, and then they are summarized according to the characteristics of various turbines. The generation mechanism, related characteristics, and suppression measures of subsynchronous oscillations caused by series complement sending. The analysis method of the subsynchronous oscillation of the current large-scale wind power sending system is described. Finally, the part that needs further research is explained.

In continuous process industries, it is essential to maintain the voltage at a specific level to ensure the smooth operation. In this paper Dynamic Voltage Restorer (DVR) method is analysed for maintaining the voltage profile. A 220V, 50Hz line is compensated with a DVR. Behavior of uncompensated line is simulated for analysis purpose and presented. Further the performance of the line is improved by compensating it with a DVR. Compensated line results are presented and compared with the results of uncompensated line. For obtaining simulation results, MATLAB Simulink v9.1 has been used. The result reveals that by using the DVR the voltage across the load is maintained at nominal value irrespective of faults and other abnormal conditions.

Objective: To improve the methods of calculation of series compensation devices (UPK), taking into account the make-away of bunch of the trains. Methods: To determine maximum losses of voltage and currents in catenary circuit the methods of probability theory and mathematic statistics were used. Results: The paper provides the technology for UPK calculation, that allows to determine the UPK capacity for between-substation zones, considering real-life traffic schedule and allowable voltage at train collectors. Practical importance: Alteration of technologies for UPK capacity calculations, in part of input data, that include traction substation transformer power, may significantly decreases the traction load power. This will allow to lower capital input for UPK installation and to decrease operational costs for UPK maintenance.

Wind generation connection to power system affects steady-state and transient stability. Furthermore, this effect increases with the increase of wind penetration in generation capacity. In this article, optimal location of flexible AC transmission system devices is carried out to solve the steady-state problems of wind penetration using a genetic algorithm. Case study is carried out on modified IEEE 39-bus system with wind penetration increases by 50%; the system suffers from outage of one generator with load decrease in one of system buses by 15%. The system suffers from minimum voltage reduction, total loss increase, and violation of power and power angle limits. Series and shunt flexible AC transmission system devices are used in this article. Results showed that series flexible AC transmission system devices in certain range are able to solve these problems associated with wind penetration in power systems with acceptable cost saving.

Optimal utilization of transmission system without congestion in the network is most important as congestion can violet the security of the system. Sufficient amount of reactive power support needs to be provided in the system in order to maintain the power flow limits on transmission lines and voltage limits at bus bars. This Paper focuses on analysis of congestion occurrence with N-1 contingencies for line flow limits in case of line and generator outages using linear sensitivity factors and congestion management using series compensation. Generation shift factor and line outage distribution factor are used to find sensitive lines and series compensation in two stages are applied to the most sensitive lines to relieve congestion. Standard IEEE 6 bus test system is used to analyze contingencies and congestion mitigation. All the simulations are performed using power world simulator version 19.0. Mathematical calculations are also performed for the same 6-bus system for validation of results.

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 capacitorcompensated lines. A multi-input multi-output (MIMO) uncertain state-space model is developed toreflect the main SSCI characteristics considering the uncertainties of wind speed, seriescompensation (SC) levels and system parameters. The SSCI is analyzed using the eigenvalueanalysis of the uncertain system model. In order to damp the SSCI between the WF and seriescapacitor compensated lines under uncertainties, an H∞ damping controller is designed for the rotorside converter (RSC). The weighting functions are designed to meet the mitigation requirements ofsub-synchronous oscillation currents and output power. The robust stability (RS) and robustperformance (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 withdifferent wind speed, and SC levels. The case study with 6 m/s wind speed and 70% SC level showssuperior performance of the H∞ damping controller.

The energy storage devices incorporated into FACTS controllers increase the operational flexibility and reduce capital cost. This paper investigates the effect of Static Synchronous Compensator with energy storage (STATCOM-ES) on dynamic bifurcations of Subsynchronous resonance (SSR). The test system considered is IEEE first benchmark model (FBM). The line is provided with fixed series compensation and active shunt compensation at the electrical center of the line. The degree of series compensation is taken as the bifurcation parameter. The results of bifurcation analysis are validated by performing transient simulation of the system.

This paper presents a damping control to mitigate sub-synchronous interactions (SSI) in doubly-fed induction generator (DFIG) wind turbines connected to series-compensated lines. This issue has gained attention due to the recent SSI phenomena reported in DFIG wind farms located near series capacitors. Two approaches which add a supplementary damping control signal are compared: one of them, integrated to the grid-side converter, and the other one, to the rotor-side converter. The SSI damping controls are designed using a multi-input multi-output state-space methodology. This allows to easily tune a high performance controller using several measurements and control inputs. Smalland large-signal stability analyses, robustness aspects, impact of the supplementary controls on the system modes, and influence of different operating conditions on the SSI are also discussed. The obtained results show that the supplementary control is able to properly damp the sub-synchronous oscillations of DFIG wind turbines by updating the existing DFIG control systems without the inclusion of expensive additional damping devices, and reducing the risk of wind generation tripping. Fil: Leon, Enrique Andres. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Bahía Blanca. Instituto de Investigación En Ingeniería Eléctrica; Argentina Fil: Solsona, Jorge Alberto. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Bahía Blanca. Instituto de Investigación En Ingeniería Eléctrica; Argentina. Universidad Nacional del Sur. Departamento de Ingenieria Electrica y de Computadoras; Argentina

This paper presents the key parameters of four different Series-Series Inductive Power Transmission (SS-IPT) configurations: (a) single phase with dual control, (b) single phase with primary side control, (c) three phase with dual control and (d) three phase with primary side control, considering two different control strategies; switching frequency and DC voltage regulations.

Doubly fed induction generator (DFIG) based wind farm connected to series compensated networks will introduce sub-synchronous resonance (SSR). Most of the studies have ignored the effect of DFIGs at different locations. In this paper, a large-scale wind farm is divided into two sub wind farms, represented by two aggregated DFIGs at different locations. Impedance models of two sub wind farms and the transmission line are established and Nyquist criterion is applied to analyze the effect of DFIGs at different locations on SSR when wind speed, series compensation degrees and the parameters of converters vary. The results show that when one of the influencing factors varies, the DFIGs near the point of common coupling (PCC) have greater impact on SSR than the DFIGs far from PCC. Finally, time domain simulation is performed in PSCAD/EMTDC, which verifies the correction of the conclusion. The method this paper proposes does not need complex calculation and can judge the impact of different factors on SSR intuitively.

Recently, sporadic power oscillations in subsynchronous frequency range were detected in several permanent magnet synchronous generator (PMSG)-based wind farms in Xinjiang, China. Given no existence of fixed series compensation in the system, it can be concluded that this is a new type of subsynchronous interaction (SSI) and different from the previous subsynchronous control interaction (SSCI) occurred in doubly-fed induction generator (DFIG)-based wind farms. Therefore, the characteristics and mechanism behind this phenomenon are so ambiguous that further clarification is needed. To investigate this new type of subsynchronous oscillations (SSO) problem, a real SSI incident is reported, and the equivalent model is established based on multi-machine equivalent aggregation. Refined frequency scan and small-signal analysis are carried out to analyse the mechanism and characteristics of such SSI. Time-domain simulations are conducted to replicate the incident. The results show that the interactions between PMSG-based wind farms and weak grids can trigger negative-resistance and capacitive-reactance effects, which leads to unstable power oscillations. To further investigate the influence of different wind power plants (WPPs), two short-circuit ratio metrics are developed, and time-domain simulations are conducted based on semi-aggregation. The potential hazards of this SSI and its mitigation strategies are also discussed and proposed.