Supplementary Subsynchronous Damping Controller Research Articles

A supplementary subsynchronous Damping Controller to damp Subsynchronous Oscillation in Muti-infeed LCC-HVDC system

As more and more clean energy sources are integrated to the power system through HVDC transmission system, two or more LCC-HVDC system will feed in to the same system forming multi-feed LCC-HVDC system. The inverters of different LCC-HVDC systems may interact with each other to cause subsynchronous oscillation. Firstly, a muti-input muti-output interconnected model with variable speed is established to investigate the cause of the oscillation. Secondly, a supplementary subsynchronous damping controller (SSDC) on each LCC-HVDC system is designed to damp the oscillation. At last, a small test system with two LCC-HVDC systems is used to verify the effectiveness of the controllers.

Time-domain simulation analysis of combined suppression measures for subsynchronous oscillators

Subsynchronous oscillation (SSO) may occur in High Voltage Direct Current (HVDC) transmission systems during operation. It seriously affects the stability of the power system, and, if no reasonable control measures are taken, the shaft system of the unit can break. To study the AC side shafting of an HVDC system, the parameters of the first IEEE standard model of SSO were taken as the reference and combined with the CIGRE Benchmark two-terminal DC transmission model to build a complete set of HVDC systems for SSO research. The system SSO phenomenon was realized by setting the fault of a Supplementary Subsynchronous Damping Controller with wideband connection and a Supplementary Excitation Damping Controller with separate modes. They were designed at the network side to suppress the SSO of the system effectively, and the effectiveness of the suppression effect was verified by time-domain simulation.

Design and Implementation of Subsynchronous Damping Controller for HVDC

The interaction between High Voltage Direct Current (HVDC) transmission lines and turbogenerator units will cause the damage of the generator shafting and the electrical system by exchanging energy at one or more lower synchronous frequencies, resulting in the damage or even breakage of the generator shafting, seriously affecting the safe operation of the power system. To solve this problem, the Supplementary Subsynchronous Damping Controller (SSDC) is an effective method to suppress the secondary synchronous oscillation of turbogenerator units connected to rectifier side caused by HVDC. This paper combines the first standard model parameters of IEEE subsynchronous oscillation with CIGRE HVDC transmission system, and builds a HVDC transmission test system for Subsynchronous Oscillations(SSO) research in PSCAD. Based on signal test method, a narrow band SSDC is designed, and the damping in each synchronization frequency band is greatly increased. When the proportional coefficient is appropriate, the electrical damping is positive. The effectiveness of the designed SSDC is also verified by time domain simulation.

Subsynchronous resonance and its mitigation for power system with unified power flow controller

Control strategy of unified power flow controller (UPFC) utilizing dq decoupling control is deduced in this paper, which can closely follow the control orders of the active and reactive power. The subsynchronous resonance (SSR) characteristics of a series compensated system equipped with UPFC are studied, and the results reveal that SSR characteristics of the system may vary significantly with UPFC in service or not. Consequently, supplementary subsynchronous damping controller (SSDC) for UPFC is proposed and investigated, and the effectiveness of the proposed SSDC is verified by damping torque analysis and time domain simulations.

Alleviation of transient torsional torque stresses of turbine generator shaft segments using CBVLC supplementary controller

In this paper a bus voltage and line current (BVLC) supplementary subsynchronous damping controller (SSDC) is proposed to alleviate subsynchronous resonance (SSR) and damping power system oscillations in a power system. Both eigenvalue investigation and time-domain simulation results verify that the proposed method can damp torsional oscillations of the power system with SVS bus voltage and line current (BVLC) supplementary controller. The results demonstrate that the proposed controller has a successful performance in minimising the SSR. It is shown that the controller is able to stabilise all unstable modes. The study is performed on the system adapted from the IEEE first benchmark model. All the simulations are carried out in MATLAB/Simulink environment.

Mitigation of SSR Oscillations in Series Compensated Line using LCAP Subsynchronous Damping Controller

Subsynchronous Resonance (SSR) is a growing problem in power systems having series compensated transmission lines. Subsynchronous resonance with low frequency that surpasses aggregate fatigue threshold of the generator shaft frequently could significantly reduce the shaft service life, which is a new problem that emerges in recent years. Flexible AC transmission systems (FACTS) controllers are widely applied to alleviate subsynchronous resonance. A line current and active power (LCAP) supplementary subsynchronous damping controller (SSDC) is proposed to damp subsynchronous resonance caused by series capacitors. Both eigenvalue investigation and time-domain simulation results verify that the proposed control strategy can effectively damping power system oscillations of the power system with SVS and SSDC. Time domain simulations using the nonlinear system model are also carried out to demonstrate the effectiveness of the proposed damping controller. The recommended control approach has been accumulated with the IEEE first benchmark model for SSR study. The analysis indicates that SVS using the proposed control strategy has better alleviation effect and output characteristics. All the simulations are validated by using MATLAB/Simulink environment.

Comparing SVC and synchronous condenser performance in mitigating torsional oscillations

This paper compares the performance of a synchronous condenser (SC) and static VAR compensator (SVC) in damping subsynchronous oscillations in a power system compensated by series capacitors by simulating different cases. In order to increase the damping of both, an auxiliary controller named supplementary subsynchronous damping controller (SSDC) is used. The generator acceleration power signal is selected as the stabilizing signal for the SSDC. To enhance the accuracy of the simulations, the impact of time delay related to the stabilizing signal is investigated. The simulation results of the different faults show that the SVC and SC are able to minimize the torsional oscillations, while the time delay has a negative effect on the performance of the SVC and SC. Hence, the performance of both in damping the oscillations is attenuated. Copyright © 2014 John Wiley & Sons, Ltd.

SSR Alleviation using BVLC Supplementary Controlled SVS of Series Compensated Power System

Abstract The sub synchronous resonance (SSR) is a substantial problem in power system having a steam turbine generator connected to a series compensated transmission system. Flexible AC transmission systems (FACTS) controllers are widely applied to mitigate SSR. In this paper, a bus voltage and line current (BVLC) supplementary subsynchronous damping controller (SSDC) is proposed to alleviate subsynchronous resonance (SSR) and damping power system oscillations in a power system. Both eigenvalue investigation and time-domain simulation results verify that the proposed method can damp torsional oscillations of the power system with SVS bus voltage and line current (BVLC) supplementary controller. The results demonstrate that the proposed controller has a successful performance in minimizing the SSR. It is shown that the controller is able to stabilize all unstable modes. The study is performed on the system adapted from the IEEE first benchmark model. All the simulations are carried out in MATLAB/SIMULINK environment.

Design of HVDC Supplementary Subsynchronous Damping Controller

Supplementary subsynchronous damping controller (SSDC) is an effective countermeasure to damp the subsynchronous oscillation (SSO) caused by HVDC. On the basis of analyzing the mechanism of inducing SSO by HVDC, the principle of damping SSO by SSDC and SSDC design methods are expounded. A SSDC is designed for a practical power plant in China, and the correctness and validity of the SSDC control strategies are proved with time domain electromagnetic simulation results.

Simulation and study on mitigation measures of frequent subsynchronous oscillation with low amplitude at multi-power plants

Subsynchronous oscillation (SSO) with low amplitude that exceeds cumulative fatigue threshold of the generator shaft frequently could significantly reduce the shaft’s service life, which is a new SSO problem that emerges in recent years. According to the real recording oscillograph, the basic reason for frequently over-threshold SSO with low amplitude at multi-power plants was analyzed based on Hulunbuir League system. The sensitivities of the electrical damping to the main electrical parameters in the contributing loop of subsynchronous torsional interaction were calculated. Based on the sensitivities, a simulation method was presented, which was used to excite the same oscillation as the actual case by exerting disturbance on the firing angle. The limitation of wide-band and narrow-band supplementary subsynchronous damping controller (SSDC) for mitigating this kind of SSO was analyzed based on the electromagnetic transient simulation model of Hulunbuir League system. The difference of supplementary excitation damping controller (SEDC) and parallel-form FACTS connected to the generator terminal was compared from the aspects of response time and the ability of damping torque supplying. The analysis indicates that their response time is similar but FACTS has stronger ability of damping torque supplying than SEDC. Time-domain simulation method was used to compare the mitigation effects of SEDC, static var compensator (SVC) and static synchronous compensator (STATCOM). Considering the mitigation effect, the floor space limit of the power plant and so on, STATCOM was considered as the best mitigation measure. A control strategy of cascaded STATCOM for engineering application was presented and the capacity for SSO mitigation as well as output characteristics was analyzed. The analysis indicates that STATCOM using the proposed control strategy has better mitigation effect and output characteristics with smaller capacity.

Application of subsynchronous damping controller (SSDC) to STATCOM

In this paper a novel supplementary subsynchronous damping controller (SSDC) is proposed for the STATic synchronous COMpensator (STATCOM) which is capable of damping out subsynchronous oscillations in power system with series compensated transmission lines. An auxiliary subsynchronous damping controller (SSDC) for a STATCOM using the generator rotor speed deviation signal as the stabilizing signal has been designed to damp subsynchronous oscillations. 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. This paper deals with a cascaded multilevel converter model, which is a 48-pulse (three levels) source converter. The IEEE Second Benchmark (SBM) model is considered for the analysis and the complete digital simulation of the STATCOM within the power system is performed in the MATLAB/Simulink environment.

Damping of subsynchronous oscillations in power system using static synchronous series compensator

In this study, a static synchronous series compensator (SSSC) is used to damp the subsynchronous oscillation in a power system compensated by the series capacitor. In order to achieve an effective damping, a supplementary subsynchronous damping controller (SSDC) is added to the SSSC. The only input signal for the SSDC is the rotor speed deviation to generate the modulation index for controlling the injected voltage of the voltage-sourced converter (VSC). Also, the chaotic optimisation algorithm is employed to tune the parameter of SSDC. The design objective is to suppress the subsynchronous resonance (SSR) caused by the series capacitor. By using the SSDC, the SSSC connected at the transmission line is able to damp the SSR. The first system of IEEE second benchmark model is used to evaluate the effective of SSDC on the torsional oscillations. The several simulations are used to demonstrate the ability of SSDC in damping the SSR.

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.

A Genetic Approach to Design a HVDC Supplementary Subsynchronous Damping Controller

A novel approach based on genetic search is presented for the design of a supplementary subsynchronous damping controller (SSDC) that is capable of damping out subsynchronous oscillation (SSO) in a parallel AC/DC transmission system. The problem of selecting the parameters of the SSDC is converted to a minimax optimization problem, which is solved by genetic algorithms with an eigenvalue-based objective function. The aim of the proposed control strategy is to choose the best controller parameters in such a way that the dominant eigenvalues of the closed-loop system are shifted to the left-hand side of s-plane as far as possible. Both the eigenvalue analysis and the detailed simulation results demonstrate the effectiveness of the proposed SSDC.

Modal control of an HV DC system for the damping of subsynchronous oscillations

A novel control scheme is presented for the design of a supplementary subsynchronous damping controller (SSDC) equipped at the rectifier end of an HVDC link that is connected in parallel with an existing resonating AC line. To stabilise the unstable subsynchronous resonance (SSR) modes, an approach based on modal control theory is developed for the design of the SSDC. Since the subsynchronous oscillations resulting from high levels of compensation on the AC line can be effectively damped out, the power transfer capability of the AC line can be enhanced by the proposed SSDC.< >