Subsynchronous Resonance In Power System Research Articles

Using a Reduced Order Robust Control Approach to Damp Subsynchronous Resonance in Power Systems

his work focuses on the use of the Linear Quadratic Gaussian (LQG) technique to construct a reliable Static VAr Compensator (SVC), Thyristor Controlled Series Compensator (TCSC), and Excitation System controller for damping Subsynchronous Resonance ( SSR ) in a power system. There is only one quantifiable feedback signal used by the controller (generator speed deviation). It is also possible to purchase this controller in a reduced-order form. The findings of the robust control are contrasted with those of the “idealistic” full state optimal control. The LQG damping controller’s regulator robustness is then strengthened by the application of Loop Transfer Recovery (LTR). Nonlinear power system simulation is used to confirm the resilience of the planned controller and demonstrates how well the regulator dampens power system oscillations. The approach dampens all torsional oscillatory modes quickly while maintaining appropriate control actions, according to simulation results.

STATCOM with SSR damping controller using geometric extraction on phase space reconstruction method

This paper proposes a method to adjust the gain control algorithm in a STATCOM controller. The salient features of this method are the automatic detection of subsynchronous resonance in power systems and the automatic gain tuning of the STATCOM controller to mitigate subsynchronous resonance. The algorithm uses controller input to produce a delay-embedded time-series plane and is implemented in the STATCOM controller to detect the time of local oscillation. A new gain value is calculated in the radius of the trajectory extracted from the geometric map using phase space reconstruction and the mitigation of voltage and reactive power oscillation is confirmed by electromagnetic transient analysis.

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.

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.

Designing of Supplementary Controller for STATCOM for Damping of Oscillations in Power System

In FACTS devices supplementary signals are widely used to enhance damping and mitigation of subsynchronous resonance in power system. Subsynchronous resonance occurs due to series capacitor in the power systems. High value of series capacitive reactance may destabilize low frequency mode which is more dangerous. There are four critical values of series compensation (XC) against which rotor oscillations may be very high in IEEE first benchmark model. In this paper modeling of STATCOM with IEEE first benchmark model is presented. Then a supplementary signal is developed which is capable to make the system stable for all critical values of series compensation. The eigenvalues are presented against all four critical values of series compensation.

Mitigation of Subsynchronous Resonance in Power System through STATCOM and Auxiliary Controller

In FACTS devices, auxiliary signals are widely used to enhance damping and mitigate Subsynchronous Resonance in Power System. Subsynchronous Resonance occurs due to series capacitor in Power System. In this paper a novel auxiliary controller of STATCOM is designed with auxiliary signal ωg i.e. accelerating frequency of generator rotor mode. Auxiliary controller is superimposed on conventional PI controller. The study system is IEEE First Benchmark Model. Alone PI is not able to damp all the modes of First Benchmark Model.

A practical method to construct network state equations in multi-machine system SSR study

Eigenvalue analysis is extensively used in power system subsynchronous resonance (SSR) study. For SSR analysis, dynamic representation of the network is required, whereas both the state variables selection and the state equations formation for the network are difficult to process especially when the system configuration is subjected to variations. Hence, it is difficult to use eigenvalue analysis for multi-machine system SSR study. This paper proposed a new method to deal with this problem. The method proposed provides a way to select network state variables without using the network proper tree, thus complex topology analysis is avoided. Meanwhile, the network state equations can be constructed and modified easily by using the defined generalized capacitor-branch admittance matrix. Therefore, this method is well suited to construct the network state equations of multi-machine systems for eigenvalue analysis of the SSR problem. The proposed method has been used in the eigenvalue analysis of a multi-machine power system in China confronting with SSR problems, and the effectiveness of the proposed method has been verified by time domain simulations.

Bifurcation control of subsynchronous resonance using TCSC

This paper presents the use of Thyristor-Controlled Series Capacitor (TCSC) to control bifurcations of subsynchronous resonance (SSR) in multimachine power system. The modified second system of the IEEE second benchmark model of subsynchronous resonance is considered. The dynamics of the damper windings, automatic voltage regulator (AVR), and power system stabilizer (PSS) on SSR in power system are included. In the case of neglecting TCSC, the results show that the operating point of the system loses stability via subcritical Hopf bifurcation. When we add TCSC to the system, all bifurcations are eliminated. Therefore, the Thyristor-Controlled compensated system never loses stability at any realistic firing angle.

On the Effect of TCSC and TCSC-Controller Gain on Bifurcations of Subsynchronous Resonance in Power Systems

The effect of thyristor-controlled series capacitor (TCSC) and its controller gain on bifurcations of subsynchronous resonance (SSR) in power system are studied. Single machine infinite bus (SMIB) power system is considered for the numerical investigations. The series compensation of the transmission line is done by either conventional variable series capacitor or TCSC . The effect of the dynamics of the damper windings is investigated. The results show that in all cases, the operating point of the system loses stability via Hopf bifurcation. Hopf bifurcation comes either in subcritical or supercritical type. Supercritical Hopf bifurcation is depicted when the dynamics of the damper windings are neglected and the line is compensated by conventional series capacitor. With the same compensation scheme i.e., conventional series capacitor, supercritical Hopf bifurcation is addressed when the dynamics of the damper windings are included. On the other hand, subcritical Hopf bifurcation is predicted when the compensation is carried out by TCSC for both cases of including and neglecting the dynamics of the damper windings. In case of supercritical Hopf bifurcation, the system routes to chaos via torus breakdown. Additionally, it is found that when the compensation is done by TCSC, the stable operating point region is enlarged. Moreover, the stable operating point region increases when the damper windings are neglected. The effect of the TCSC controller gain on the locations of the Hopf bifurcation has also been studied.

On the Effect of Turbine Governor Gain on Bifurcations of Subsynchronous Resonance in Power Systems

This paper presents the effect of turbine governor (TG ) gain on the bifurcations of subsynchronous resonance (SSR) in power systems. The first system of the IEEE second benchmark model of SSR is considered for the numerical simulations. As the compensation factor increases, the power transfer capability of the transmission line increases. However, the operating point loses stability via supercritical Hopf bifurcation. On further increase of the compensation factor beyond the Hopf bifurcation, the system routes to chaos via torus breakdown. It is found that the value of the TG gain affects the location of the Hopf bifurcation point. High value of TG gain stabilizes the operating point of the system at all realistic compensation factor and therefore eliminates all bifurcations of the system. Time-domain simulation results of the nonlinear dynamical mathematical model carried out at different governor gains and two operating conditions agree with the results of the eigenvalue analysis.

On the effect of AVR gain on bifurcations of subsynchronous resonance in power systems

This paper presents the effect of the automatic voltage regulator (AVR) gain on the bifurcations of subsynchronous resonance (SSR) in power systems. The first system of the IEEE second benchmark model of SSR is chosen for numerical investigations. The dynamics of both axes damper windings of the generator and that of the power system stabilizer (PSS) are included. The bifurcation parameter is the compensation factor. Hopf bifurcation, where a pair of complex conjugate eigenvalues of the linearized model around the operating point transversally crosses from left- to right-half of the complex plane, is detected in all AVR gains. It is shown that the Hopf bifurcation is of subcritical type. The results also show that the location of the Hopf bifurcation point i.e. the stable operating point regions are affected by the value of the AVR gain. The variation of the location of the Hopf bifurcation point as function of the AVR gain for two operating conditions is obtained. Time domain simulation results based on the nonlinear dynamical mathematical model carried out at different compensation factors and AVR gains agree with that of the bifurcation analysis.

Generalised eigenvalue and complex-torque-coefficient analysis for SSR study based on LDAE model

A linearised differential-and-algebraic-equation (LDAE) model for power-system subsynchronous-resonance (SSR) study is proposed. The LDAE model can be established quickly according to the element LDAE models and network topology. Generalised eigenvalue and complex-torque-coefficient analysis for SSR study based on the LDAE model is presented. The effectiveness of the proposed SSR-study methods is verified through computer test results. The suggested LDAE model and its relevant analysis methods have the potential to work jointly with appropriate HVDC transmission and FACTS-device models for SSR study and to obtain deep insight about their effects on SSR.

Controlling Chaos and Bifurcation of Subsynchronous Resonance in Power System

Linear and nonlinear state feedback controllers are proposed to control the bifurcation of a new phenomenon in power system, this phenomenon of electro-mechanical interaction between the series resonant circuits and torsional mechanical frequencies of the turbine generator sections, which known as Subsynchronous Resonance (SSR). The first system of the IEEE second benchmark model is considered. The dynamics of the two axes damper windings, Automatic Voltage Regulator (AVR) and Power System Stabilizer (PSS) are included. The linear controller gives better initial disturbance response than that of the nonlinear, but in a small narrow region of compensation factors. The nonlinear controller not only can be easily implemented, but also it stabilizes the operating point for all values of the bifurcation parameter.

Damping subsynchronous resonance in power systems

An idea is presented for damping SSR in power systems using a double-order SVS auxiliary controller in combination with continuous controlled series compensation (CCSC) and an induction machine damping unit (IMDU) coupled with the T–G shaft. A linearised dynamic model of continuous controlled series compensation has been derived and incorporated. The eigenvalue analysis using the linearised model for continuous operation of CSC in combination with an induction machine damping unit (IMDU) and a double-order SVS auxiliary controller (DOAC) has been applied. It is seen that all the unstable torsional modes of various frequencies are stabilised effectively. A time-domain modulation study has also been performed using the nonlinear model to demonstrate the effectiveness of the proposed scheme under large disturbance conditions. The scheme enhances the system performance considerably and torsional oscillations are damped out at all levels of series compensation and effective control of power flow is obtained.

Book Reviews: Analysis of Subsynchronous Resonance in Power Systems, Signal Analysis and Prediction, Video Coding: An Introduction to Standard Codecs, Control Systems Engineering

Book Reviews: Analysis of Subsynchronous Resonance in Power Systems, Signal Analysis and Prediction, Video Coding: An Introduction to Standard Codecs, Control Systems Engineering

Application of Bifurcation Theory to Subsynchronous Resonance in Power Systems

A bifurcation analysis is used to investigate the complex dynamics of a heavily loaded single-machine-infinite-busbar power system modeling the characteristics of the BOARDMAN generator with respect to the rest of the North-Western American Power System. The system has five mechanical and two electrical modes. The results show that, as the compensation level increases, the operating condition loses stability with a complex conjugate pair of eigenvalues of the Jacobian matrix crossing transversely from the left- to the right-half of the complex plane, signifying a Hopf bifurcation. As a result, the power system oscillates subsynchronously with a small limit-cycle attractor. As the compensation level increases, the limit cycle grows and then loses stability in a secondary Hopf bifurcation, resulting in the creation of a two-period quasiperiodic subsynchronous oscillation, a two-torus attractor. On further increases of the compensation level, the quasiperiodic attractor collides with its basin boundary, resulting in the destruction of the attractor and its basin boundary in a bluesky catastrophe. Consequently, there are no bounded motions. The results show that adding damper windings may induce subsynchronous resonance.

Application of an auxiliary controlled static var system for damping subsynchronous resonance in power systems

In this paper a novel concept of a static var system (SVS) auxiliary controller application for damping subsynchronous resonance in power systems has been proposed and demonstrated. An SVS controller, known as the combined reactive power and frequency (CRPF) auxiliary controller has been developed and incorporated in the SVS control system located at the middle of a series compensated long transmission line. The studies are conducted on a system having a similar spread of the torsional modes as the first IEEE benchmark model. The proposed SVS auxiliary controller stabilizes all the torsional modes over a wide operating range. A digital computer simulation study has been performed, using a nonlinear system model, to illustrate the effectiveness of the proposed SVS auxiliary controller.

An LQG based PSS design for controlling the SSR in power systems with series-compensated lines

This paper presents a linear quadratic Gaussian (LQG) based-power system stabilizer (PSS) to control the subsynchronous resonance (SSR) that may occur in a series capacitor compensated power system. This paper investigates the dominant parameters on the SSR using the critical compensation level (CCL), and selects the design parameters to confirm the stability robustness. The complete SSR simulation system based on the IEEE first benchmark is employed in this study. Eigenvalue analysis and time domain simulations using a nonlinear system model show that the proposed PSS can control the SSR efficiently.

Damping subsynchronous resonance using superconducting magnetic energy storage unit

A novel damping scheme using superconducting magnetic energy storage (SMES) unit is proposed in this paper to damp subsynchronous resonance (SSR) of the IEEE Second Benchmark Model, system-1 which is a widely employed standard model for computer simulation of power system SSR. The studied system contains a turbine-generator set connected to an infinite bus through two parallel transmission lines, one of which is series-capacitor compensated. In order to stabilize all SSR modes, simultaneous active and reactive power modulation and a proportional-integral-derivative (PID) damping controller designed by modal control theory are proposed for the SMES unit. A frequency domain approach based on eigenvalue analysis and time-domain approach based on nonlinear model simulations are performed to validate the effectiveness of the damping method. It can be concluded from the simulation results that the proposed damping scheme can effectively suppress SSR of the studied system. >