Mitigation Of Subsynchronous Resonance Research Articles

FUZZY LOGIC CONTROLLED STATCOM WITH A SERIES COMPENSATED TRANSMISSION LINE ANALYSIS

The integration of wind farms with transmission networks exhibits several problems. The sub-synchronous resonance (SSR) plays a vital role in those issues, and it must be reduced. Two effective flexible ac transmission system (FACTS) based voltage control devices, namely static synchronous series compensator (SSSC) and static compensator (STATCOM) are proposed in this paper to mitigate the SSR. Detailed eigenvalue analysis was conducted to prove the successful mitigation of SSR by two controllers in a series of compensated wind farms. To find the dominant control scheme, the eigenvalues of the proposed controllers are compared with PSCAD/EMTDC simulations. Finally, a comparison study is carried out between the two proposed SSR controllers.Further, the fuzzy logic control based on STATCOM and SSSC is also developed to enhance the stability margin of the wind turbine. The results have been validated with the IEEE 1st SSR benchmark system. From the results, it is proven that Fuzzy Logic Controller (FLC) based SSSC exhibits better performance than STATCOM.

Event-Triggered robust control scheme for sub-synchronous resonance mitigation in DFIG-based WECS

Series compensation is an economically feasible solution for facilitating the integration of high levels of wind energy sources into the grid. However, high levels of series compensation in transmission lines typically results in sub-synchronous resonance (SSR) in doubly-fed-induction-generator (DFIG)-based wind energy conversion systems (WECS). The introduction of negative equivalent resistance due to negative SSR slip results in self-sustaining oscillating instability and potentially loss of stability of the whole system. This paper proposes an event-triggered sliding mode control (ETSMC)-based control approach for the effective damping of sub-synchronous resonance. The ETSMC control is designed for the rotor side converter of the DFIG, and a phase compensator unit is augmented with the ETSMC control to enhance its efficacy in mitigating specific unstable mode. The proposed control approach is validated using a DFIG-based WECS in IEEE first benchmark model. The results prove the high efficacy of the control approach in mitigating SSR and ensuring system’s fast recovery. In addition to the attributes of the SMC approach, reliance on an event triggering mechanism leads to only seldom control updates, thereby solving the problem of requirement of high communication bandwidth and computational power.

Mitigation of Subsynchronous Resonance for Grid-Connected Inverters in Series-Compensated Weak Power Grids Through Observed Q-Axis Grid Voltage Feedback

Series compensations have been widely used in modern power systems to extend the power transfer capacity. Since more and more renewable power generation systems are installed in power systems, the grid-connected inverters (GCIs) used by the renewable power generations may interfere with series-compensated power lines, which introduce subsynchronous resonance (SSR) causing power system failure that has been observed in real cases. The phase-locked loop (PLL) of the GCI's control system is the main factor that can cause the SSR in the series-compensated power grid. To mitigate the impact of the PLL and obtain the stable operation of the power system, a <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">q</i> -axis voltage feedback method has been proposed in literature to damp the harmonic oscillations in the weak power grid where, however, the series compensation is not considered. Because the real <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">q</i> -axis voltage cannot be obtained, the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">q</i> -axis voltage output from the PLL is used as the feedback variable in literature. However, due to the dynamic response of the PLL, the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">q</i> -axis voltage output from the PLL is different from the real <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">q</i> -axis voltage, and the direct use of it for the damping of the SSR in the power grid with series compensations is invalid, which is investigated in this article. Besides, an observed <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">q</i> -axis voltage feedback method is proposed in this article to damp the SSR in the series-compensated power grid with GCIs being connected. By putting an observer in the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">q</i> -axis voltage feedback path, the real <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">q</i> -axis voltage can be estimated and applied to damp the SSR. Simulation and experimental results have been provided to verify the effectiveness of the proposed observed <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">q</i> -axis voltage feedback method in the damping of the SSR.

Modelling and control of static synchronous series compensator interfaced with DFIG-based wind farm using PSO for SSR alleviation

Subsynchronous resonance (SSR) in wind turbine generators interfaced with series compensated transmission line has been explored in recent few years. Instead of torsional interaction (TI), the induction generation effect (IGE) prompts SSR in such systems. The mitigation of SSR using flexible ac transmission system (FACTS) devices like a thyristor-controlled series capacitor (TCSC), gate-controlled series capacitor (GCSC), static var compensator (SVC) and static synchronous compensator (STATCOM) has been researched in the literature. However, in wind turbine generators, the efficacy of static synchronous series compensator (SSSC) to mitigate SSR is relatively less explored. This paper presents mathematical modelling of SSSC and a study of hybrid series compensation of transmission line using SSSC and fixed series capacitor (FSC) to diminish the SSR effect in doubly-fed induction generator (DFIG)-based wind farm. The values of controller parameters of SSSC for SSR mitigation are identified using particle swarm optimisation (PSO) and compared with the Ziegler and Nichols (Z–N) method. Results obtained through PSO are more precise and finer than the conventional approach. The eigenvalue analysis and fast Fourier transform (FFT) analysis are shown to demonstrate the damping offered by SSSC to SSR oscillations along with transient simulations. The impact of SSR at different compensation levels and wind speed is examined, and the effectiveness of SSSC for SSR mitigation is illustrated using the hybrid compensation method. The risk of SSR is high at low wind speeds and a high compensation level. In such instances, it is shown that SSSC is capable of effectively alleviating SSR.

RETRACTED: Novel transient stability analysis of grid connected hybrid wind/PV system using UPFC

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.

SSR Alleviation in SCIG-Based Wind Power Plants Using Resistive Bridge-Type FCL

Series-Compensated Transmission Lines (SCTLs) are widely used for connection of large scale wind power plants (WPPs) to the power system to transmit the active power generated from WPPs. However, it can lead to sub synchronous resonance (SSR) phenomena in WPPs connected with SCTLs. Also, capacitive compensation of transmission lines reduces the line impedance, which leads to increasing short circuit current level in WPPs. This study proposes the resistive bridge-type fault current limiter (RBFCL) for SSR mitigation and limiting short circuit current in WPPs connected with SCTLs. Also, its performance is compared with the static synchronous compensator (STATCOM) and thyristor controlled series capacitor (TCSC) to demonstrate the effectiveness of the RBFCL in terms of SSR mitigation. The WPP used in this paper is modelled based on an aggregated squirrel-cage induction generator (SCIG) derived by an aggregated wind turbine (WT). The PSCAD/EMTDC software and the IEEE first benchmark model are used for this study. Simulation results demonstrate that the RBFCL not only limits the short circuit current contribution of WPPs, but also effectively damps the SSR oscillations due to IGE as well as TI, when the WPP is subjected to a large disturbance.

Analysis and Mitigation of Subsynchronous Resonance in Series-Compensated Grid-Connected System Controlled by a Virtual Synchronous Generator

Analogizing the subsynchronous resonance (SSR) phenomenon of the series-compensated grid-connected system based on synchronous generator, the virtual synchronous generator (VSG) also has the low-frequency oscillation problem owing to the impedance interaction between VSG and series-compensated network. Stability of the series-compensated grid-connected system controlled by VSG is analyzed by the impedance-based Nyquist stability criterion. Due to the inductive impedance of VSG, VSG is easy to couple with the series-compensated network in the low-frequency areas, which can lead to the SSR. With the increase of the series compensation level, the stability of VSG becomes worse and the induced oscillation frequency becomes higher. Therefore, a modulation signal feedforward active-damping control strategy with time-delay compensation is proposed to suppress this SSR, which directly feeds the active-damping control signal to the pulsewidth modulation modulator for reshaping the output impedance of VSG from the inductance to the resistance–inductance. Moreover, a value range of virtual resistance is given with considering the influence on the regular operation of VSG. Finally, the simulation and experimental results verify the correctness of the SSR analysis and the feasibility of the proposed active-damping control strategy.

Erratum to “Mitigation of Subsynchronous Resonance Induced by a Type III Wind System” [Jul 20 1717-1727

There was a typo in the name of the primary author in the above named paper. It should have appeared as Hooman Ghaffarzadeh.

Robust finite-time controller for damping of subsynchronous resonance in doubly fed induction generator wind farm

To alleviate subsynchronous resonance in doubly fed induction generator–based wind farm, this study devises a robust nonlinear control for a rotor-side converter based on a fractional-order sliding mode controller. The designed fractional-order sliding mode controller is able to realize finite-time control and reduce the control time compared with terminal sliding mode control, which contributes to the faster mitigation of subsynchronous resonance. Impedance-based analysis and transient simulation are carried out to evaluate the performance of the fractional-order sliding mode controller compared with terminal sliding mode control and subsynchronous damping control. Simulation results verify that the fractional-order sliding mode controller is able to damp SSR within shorter time and effectively reduce the fluctuation range of a system’s transient responses under various working conditions of compensation degrees and wind speeds. Furthermore, the fractional-order sliding mode controller enhances the robustness under external disturbance and parametric uncertainty, ensuring safe operation of the practical wind farm.

Analysis and Mitigation of Sub-Synchronous Resonance for Doubly Fed Induction Generator under VSG Control

This paper presents the analysis and mitigation of sub-synchronous resonance (SSR) for doubly fed induction generators (DFIG) under virtual synchronous generator (VSG) control, based on impedance methods. VSGs are considered to have grid-supporting ability and good stability in inductance-based weak grids, and are implemented in renewable power generations, including DFIG systems. However, stability analyses of VSGs for DFIG connecting with series capacitor compensation are absent. Therefore, this paper focuses on the analysis and mitigation of SSR for DFIG under VSG control. Impedance modeling of DFIG systems is used to analyze SSR stability. Based on impedance analysis, the influence of VSG control parameters and the configuration of damping factor of reactive power are discussed. Next, a parameter configuration method to mitigate SSR is proposed. Finally, time-domain simulation and fast fourier transform (FFT) results are given to validate the correctness and effectiveness of the impedance model and parameter configuration methods.

BPF based Estimation and Mitigation of SSR with SSSC

The risk of Subsynchronous Resonance (SSR) may reduce with the hybrid of active and passive series compensations. The hybrid series compensation can be done with Static Synchronous Series Compensator (SSSC) (an active FACTS device) and fixed series capacitor (passive compensation). In this paper, we propose a Band Pass Filter (BPF) based Subsynchronous Damping Controller (SSDC) with SSSC. The aim of the paper is to increase the damping of all critical TMs with minimum number of highly frequency selective BPFs. The BPFs are used to extract the subsynchronous frequency components from electrical network. The extracted subsynchronous frequency components are used to modulate the reference value of SSSC injected voltage. Thereby, the SSSC injecting voltage can suppress the subsynchronous currents flowing in the transmission network. The linear (DQ) model is developed in MATLAB-Simulink using the differential and algebraic equations of the system. The damping torque, eigenvalue and transient simulation methods are performed with the linear model to carry out the analysis of SSR. The eigenvalue analysis is used to select the number of filters. The number of BPFs is selected in view of suppressing the torsional vibrations at all critical frequencies. The outcomes of the paper show that the negative damping is considerably diminished with the proposed SSDC in the entire range of torsional mode frequencies and mitigate SSR.

Unit Template Based Control Design for Alleviation and Analysis of SSR in Power System Using STATCOM

—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 the effect of static synchronous compensator (STATCOM) for mitigation of SSR in a single machine infinite bus system. The mathematical modeling is presented in the form of linearized equations, which can be used for eigenvalue analysis of SSR. A novel control technique based on unit template algorithm is incorporated in STATCOM for alleviation of SSR and it proves to be ingenious in damping out all the oscillations. Furthermore, frequency scan and fast Fourier transform (FFT) analysis are presented, that provide resonant frequencies at different levels of compensation and dominant modes of oscillations respectively. To examine and authenticate the efficacy of the proposed controller, the IEEE second benchmark model on SSR is simulated in MATLAB/Simulink environment and the results are analyzed to illustrate the potency of the proposed control strategy.

Mitigation of Subsynchronous Resonance Induced by a Type III Wind System

This paper proposes an adaptive supplementary controller based on the multiple-model adaptive control (MMAC) approach to mitigate subsynchronous resonance (SSR) induced by a Type III wind system connected to a series-compensated transmission line. The proposed supplementary controller has two levels; the first level is a set of controllers designed using standard linear control methods, and the second level is a supervisory controller that selects the level-one controller based on the system conditions. A systematic approach is introduced for simultaneous coordination of parameters of the proposed supplementary controllers in a nonaggregated wind system. The aim of this coordination approach is to stabilize the system by moving the unstable modes to the left-hand plane while minimizing the controller gain values to reduce the sensitivity of the wind generator to the small disturbances. To evaluate the performance of the proposed controller, small-signal stability of the test system is studied using its comprehensive dynamic model. Time-domain simulation results show the effectiveness of the proposed supplementary controller to mitigate subsynchronous oscillations in a wide range of operating conditions.

Dynamic bifurcation analysis and mitigation of SSR in SMIB system

This paper presents a detailed study on Sub-synchronous resonance in a Single machine connected to an infinite bus system by employing Bifurcation Theory. The synchronous machine model considered is a two-axis model, the turbine system is a six mass system. A comparative study of Sub-synchronous resonance for the two-axis synchronous machine models 1.1, 2.1 and 2.2 under constant excitation is presented in this paper. The effect of adding an exciter, power system stabilizer and Static Synchronous Series Compensator to the SMIB system, incorporated with a 2.2 synchronous machine model on the bifurcations of SSR is also investigated. The results obtained on replacing the fixed series compensation of the line by Static Synchronous Series Compensator resulted in the mitigation of Sub-synchronous Resonance. The results obtained for all the above-considered cases are compared with eigenvalue analysis and validated using transient analysis&lt;strong&gt;.&lt;/strong&gt;

Replicating Real-World Wind Farm SSR Events

In 2017, three sub-synchronous resonance (SSR) events were reported in the transmission system of Electric Reliability Council of Texas (ERCOT). These three events with different consequences are due to the same cause, i.e., Type-3 wind farms radially connected to a series compensated transmission line. The objectives of this paper are: 1) to build a testbed to replicate these real-world events and investigate what causes the different consequences; 2) to find out the impact of wind penetration level and wind speed on SSR; and 3) to investigate how to mitigate SSR. The replication testbed is built in MATLAB/Simpowersystems with each wind farm represented by a single aggregated wind turbine with full dynamics. The challenge of replication is the limited information about those three events, the ERCOT system, and the wind farms. Nevertheless, relying on simplification and assumptions, we are able to replicate the three events. Our contributions include the configured testbed for Type-3 wind farm SSR studies, diagnosis of impacting factors on SSR, and the confirmation of an SSR mitigation strategy through grid-side converter ac voltage command signal modulation.

Analysis and Mitigation of Subsynchronous Resonance in a Korean Power Network with the First TCSC Installation

This paper presents a detailed analysis results of the effect of a thyristor-controlled series capacitor (TCSC) on subsynchronous resonance (SSR), which was first applied to a Korean power system. First, the TCSC parameters were calculated, the structure of TCSC with synchronous voltage reversal (SVR) controller was presented, and the torsional characteristics of Hanul nuclear power generator rotor were studied to investigate the natural frequency and mode shape. The test signal method was used to determine the electrical damping in the frequency range of SSR operation through an electromagnetic transient analysis program in various system configurations. The SSR phenomenon was analyzed by comparing the electrical and mechanical damping of a conventional fixed series capacitor (FSC), and the case of a TCSC installed, and the effectiveness of the TCSC without any risk of SSR was demonstrated. As a result, when installing FSC, SSR occurred under sensitive operating conditions, but SSR was prevented in the case of TCSC compensation with SVR. The results obtained in this study can be effectively applied to the installation of TCSC in real power systems.

Analysis and mitigation of subsynchronous resonance based on integral control for DFIG‐based wind farm

Series capacitor compensation technology has been widely used in long-distance wind power transmission, which can improve the power transmission capacity and enhance the static stability of the power system. However, adding a series capacitor in the line may present a potential risk of subsynchronous resonance (SSR) to the system. This study focuses on the SSR caused by induction generator effect of the doubly-fed induction generator-based wind farms. The SSR phenomenon of wind power system is researched by the impedance analysis method. A mitigation strategy of adding a virtual inductance based on integral control is proposed for enhancing the system stability and alleviating the SSR. It has clear and intuitive physical concept, which is beneficial to system integration and provides a simpler and more economic method for mitigating SSR. Moreover, the principle and process of controller design are elaborated. Moreover, the time-domain simulation is carried out to prove the effectiveness of the proposed control strategy under different operating conditions considering various compensation levels and wind speeds. Finally, the suppression effects of the virtual inductance in rotor-side converter and grid-side converter are compared.

SUBSYNCHRONOUS RESONANCE MITIGATION USING WIDE AREA MEASUREMENT SYSTEM

This paper presents the wide area measurement based controller for subsynchronous resonance mitigation in two machine system. The dq0 model of the two machine system.is considered in this paper. Generator 1 is multimass model as per given in IEEE first bench mark model and genereator 2 is considered as lumped model. The computation of frequency from voltage phasor of each generator is used for SSR mitigation. The difference of frequency of two machine is used as control signal . This control signal modulate the firing angle of thyristor controlled reactor through controller .As the control signal is global signal ,it will give damping to almost all torsional modes of oscillation and eliminates local controller for each torsional modes. This paper shows application of wide area controller in dq0 model mitigates subsynchronus oscillation in system.

Mitigation of Subsynchronous Resonance in Series-Compensated DFIG Wind Farm Using Active Disturbance Rejection Control

This paper presents an active disturbance rejection control (ADRC) method to mitigate subsynchronous resonance (SSR) in a doubly-fed induction generator (DFIG)-based wind farm connected to series compensated transmission lines. First, the frequency of the SSR and its influencing factors are analyzed, and the limitation of the traditional damping controller based on phase compensation is discussed. Then, a damping controller is designed using the ADRC method, which is adapted to the uncertainty SSR frequency of wind farms. The stator current of the DFIG that contain apparent SSR frequency is adopted as the input signals of the ADRC damping controller, and the outputs are added to the current inner loop of the rotor side converter (RSC), which has fast response speed. The performances of the ADRC damping controller are tested in different compensation levels, numbers of DFIG in wind farm, and parameters of the converter control. The simulation results indicate that the ADRC damping controller is superior to the traditional damping controller for mitigating the SSR because it can automatically estimate and compensate the uncertainty disturbances.

Variable Speed Pump Storage for the Mitigation of SSR in Power System with Wind Generation

Subsynchronous resonance (SSR) can bring significant negative effects on the grid system like stability, security, and even generator shaft damage. This work presents a new method of using a doubly‐fed induction machine (DFIM) based system of variable speed pumped storage plant (VSPS) to mitigate SSR in the power system with high penetration of wind generation. The mitigation is reached based on the principle of balanced shaft mechanical input power and electromagnetic power. The fundamental concepts and phenomena of SSR with wind farm are discussed in brief in this work. For the sake of analysis and verification of performance of the proposed system, the network model including wind farm, VSPS, HVDC, and synchronous machine is built based on Ningxia grid for the SSR study using PSCAD platform. The result shows that VSPS brings significant effect to dampen the SSR in the power system with high penetration of wind generation.