Subsynchronous Oscillations In Power Systems Research Articles

A novel excitation controller to damp subsynchronous oscillations

A novel supplementary subsynchronous damping controller (SSDC) is proposed for the generator excitation system which is capable of damping out subsynchronous oscillations in power systems with series compensated transmission lines. It is shown that the controller is able to stabilize all unstable modes for all compensation ratios. Eigenvalue analysis and transient simulations of detailed nonlinear system are considered to investigate the performance of the controller. Robustness of the controller has been analyzed by facing the system with disturbances leading to significant changes in generator operating point. The IEEE Second Benchmark Model is considered as the system under study. All the simulations are carried out in MATLAB/SIMULINK environment.

Application of superconducting magnetic energy storage unit for damping of subsynchronous oscillations in power systems

A novel strategy for suppressing subsynchronous resonance (SSR) in power systems using a superconducting magnetic energy storage (SMES) unit is presented. The energy transfer between the power system and the SMES unit is based on simultaneous control of active and reactive power modulation of the SMES unit. The active power is controlled by an artificial neural network (ANN) based controller, while the reactive power is controlled by a conventional regulator. The gains of the controllers are determined from the power system operating conditions and the rating of the SMES unit. Unequal α-mode of firing angle control of the converters is utilized to enforce zero energy transfer in the SMES unit under steady state conditions. The proposed scheme is tested using the IEEE first benchmark model for subsynchronuos oscillations, and it is found that, with the proposed mode of control, the SMES unit can effectively restore power system stability.

A bifurcation analysis of subsynchronous oscillations in power systems

A bifurcation analysis is used to investigate the complex dynamics of a heavily loaded turbine-generator system connected to an infinite busbar through a series capacitor-compensated transmission line. It reveals the existence of self-excited subsynchronous torsional oscillations of a 5-mass rotor, which may eventually lead to the destruction of the shaft or the loss of synchronism of the generator. Specifically, we show that, as the capacitor-compensation value increases and reaches a critical value, called supercritical Hopf bifurcation, the system around the operating point undergoes small single-period oscillations with constant amplitude. This in turn results in a small limit-cycle attractor. As the compensation level increases further, the amplitude of oscillation grows until a secondary Hopf bifurcation is reached. There, the oscillations characterize themselves by two incommensurate periods and bounded amplitudes, signifying the transformation of the limit cycle into two-period quasiperiodic motion called a two-torus attractor. When the capacitor-compensation level passes a third critical value, the amplitude of oscillations becomes unbounded following the destruction of the two-torus attractor and its basin of attraction in a so-called bluesky catastrophe. Interestingly, this scenario repeats itself in the vicinity of three supercritical Hopf bifurcations. The bifurcation analysis is validated with numerical solutions of the differential equations that govern the power system.

Correction to "Application of a Thyristor Controlled var Compensator for Damping Subsynchronous Oscillations in Power Systems"

Correction to "Application of a Thyristor Controlled var Compensator for Damping Subsynchronous Oscillations in Power Systems"

Application of a Thyristor Controlled var Compensator for Damping Subsynchronous Oscillations in Power Systems

Application of a Thyristor Controlled var Compensator for Damping Subsynchronous Oscillations in Power Systems

Application of a Thyristor Controlled Var Compensator for Damping Subsynchronous Oscillations in Power Systems

This paper presents a new concept for controlling static VAr compensators (SVC) in power systems. It allows thyristor controlled VAr compensators to effectively damp subsynchronous resonance (SSR) oscillations besides controlling the system voltage. Eigenvalue analysis and digital time simulations for the IEEE SSR benchmark system are utilized to investigate the role of the main voltage regulator of the SVC in stabilizing the system and alleviating the SSR modal interactions that may be introduced by the auxiliary speed signal alone. Stability zones are identified to optimize the compensator parameters for economical application.

Application of Static VAR Compensators and HVDC Converters for Damping Subsynchronous Oscillations in Power Systems

A new concept for controlling thyristor-controlled static VAr compensators and HVDC converters in power systems is presented. With such a concept it is possible to damp all low frequency (including subsynchronous) oscillations besides controlling the system voltage. For developing this controller a pole shifting approach is utilized. Eigenvalues are used for the analysis of the problem and determining system damping for all modes of oscillations. To support the analytical results, time simulations of the complete non-linear system are presented.

Damping of Subsynchronous Oscillations By an HVDC Lins. An HVDC Simulator Study

Subsynchronous oscillations in power systems with series compensated lines can be amplified and sustained due to interaction between the electrical power system and the turbine generator mechanical system. Recently it has been found that also an HVDC link may have a similar effect especially when connected near a turbine generator as the only load.

Subsynchronous oscillations part 1 ߞ comprehensive system stability analysis

This paper describes a frequency response method for analyzing the stability of subsynchronous oscillations in power systems, as modeled by a number of synchronous machines and an extensive series compensated transmission network. This method allows the simultaneous detailed modeling of all machine shafts and control loops, and hence permits investigation of possible interaction in the subsynchronous oscillation frequency band between machines in different plants. An example application of the method indicates that such interactions may, indeed, occur.