Analysis and mitigation of subsynchronous oscillations in a radially-connected wind farm
TL;DR: In this article, a voltage regulator model of series compensated power system is proposed and linear state space model of SVC is developed for mitigating subsynchronous oscillations (SSO).
Abstract: Subsynchronous oscillations (SSO), especially, subsynchronous resonance are potential problems in series compensated power system. A fixed speed wind farm employing single cage induction generator (IG) and double cage IG connected to series compensated line are prone to SSR problem. This paper presents some investigations on SSO resulting from induction generator effect (IGE) with the wind turbine generator (WTG) modelled either as single cage IG or double cage IG. Eigenvalue analysis is carried out for various levels of series compensation for different sizes of wind farm with varying power outputs. Eigenvalue analysis is validated by the electromagnetic transient simulations using PSCAD/EMTDC software. The possibility of steady state SSR (IGE) and transient SSR is investigated in depth using PSCAD/EMTDC for the modified IEEE first bench mark (MFBM) model. SVC is employed for mitigating SSR. A new voltage regulator (VR) model of SVC is proposed and linear state space model of SVC is developed. Eigenvalue analysis conducted with the proposed voltage regulator reveals that the proposed VR model is more effective in mitigating SSR compared to VR models that are reported in the literature.
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TL;DR: This study presents an overview of potential SSCI mitigation techniques at various stages of the power system, including system planning, operation, control, and protection phases at both network and generation sides and reviews the active damping controls utilizing flexible ac transmission systems and WTC controls.
Abstract: Subsynchronous control interaction (SSCI) associated with wind farms has become one of the major challenges for maintaining the stability and reliability of modern power systems. SSCI is mainly caused by the active participation of fast-acting wind turbine converter (WTC) controls in the phenomenon. It can damage the system equipment, reduce the amount of power generation, and degrade the power quality. Thus, it is urgent to develop practical mitigation techniques for the SSCI in order to achieve a smooth and reliable operation of grid interfaced wind farms. This study presents an overview of potential SSCI mitigation techniques at various stages of the power system, including system planning, operation, control, and protection phases at both network and generation sides. In particular, this paper reviews the active damping controls utilizing flexible ac transmission systems (FACTS) and WTC controls. Finally, it outlines the challenges and future work in studying SSCI mitigation techniques in practical wind power systems.
70Â citations
DOI•
01 Jan 2014
TL;DR: This paper studies three different possibilities for the addition of controllers that perform SSR damping to eliminate induction generator effect SSO (SSIGE) in series compensated doubly-fed induction generator (DFIG) based wind farms.
Abstract: This paper is part II of a two-paper series that reviews, analyzes, and explores mitigation methods for sub-synchronous resonance (SSR) in series compensated doubly-fed induction generator (DFIG) based wind farms. The paper studies three different possibilities for the addition of controllers that perform SSR damping to eliminate induction generator effect SSO (SSIGE): controllers can be added to (1) thyristor-controlled series capacitor (TCSC) (2) gate-controlled series capacitor (GCSC), or (3) DFIG grid-side converter (GSC) controller. The first and second cases are related to the series flexible AC transmission systems (FACTS) family, and the third case uses the DFIG converters themselves to damp the SSR. In order to better understand this part II, it is highly recommended that part I of the two-paper series be studied first.
12Â citations
Cites methods from "Analysis and mitigation of subsynch..."
...In [12], [19] - [20], a static var compensator (SVC) has been employed in FSWTGS to mitigate the SSR....
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TL;DR: An accurate analysis of the instability in DFIG-based wind farms due to the use of series compensation and provided maximum power extraction from these farms using the high compensation without the unstable sub-synchronous oscillation occurrence is presented.
Abstract: This paper presented an accurate analysis of the instability in DFIG-based wind farms due to the use of series compensation and provided maximum power extraction from these farms using the high compensation without the unstable sub-synchronous oscillation occurrence. For this purpose, using modal analysis, it is first shown that the main cause of this instability is low wind speed in the high compensation. This issue causes the series compensated DFIG-based wind farms is unstable due to a sub-synchronous mode. In order to prevent the unstable sub-synchronous oscillation occurrence, a supplementary controller called SSRIPC and DFIG controllers are used. Also, for good dynamic response and proper use of the SSRIPC, an objective function considered based on three factors of minimum damping ratio, overshoot, and settling time of the oscillations. By accurate optimization of the proposed controller using root-locus and PSO algorithm, it is prevented the instability caused by sub-synchronous resonance and sub-synchronous control interaction that are classes of the sub-synchronous oscillations. IEEE SSR first benchmark model and MATLAB/Simulink software are used to validate the performance of the proposed method.
9Â citations
Cites background from "Analysis and mitigation of subsynch..."
...In [7] and [8], the line current was considered for the feedback signal of the SVC to damp the SSR in DFIG-based wind farms....
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TL;DR: A detailed model-based time-domain simulation results show that O-ADRC can effectively mitigate the SSCI under different operating conditions and provide sufficient damping for the DFIG-based wind farms.
Abstract: Recently, a new type of subsynchronous oscillation (SSO) has occurred in doubly-fed induction generator (DFIG)-based wind farms. This oscillation is also called the subsynchronous control interaction (SSCI), which is mainly caused by the interaction between the transmission series compensation and the DFIG controller. Therefore, the oscillation frequency of the SSCI is susceptibly impacted by DFIG operating conditions, which presents major challenges to conventional mitigation strategies. To solve this problem, a grid-connected series-compensated DFIG-based wind farm is established, and the formation process of the SSCI is analysed. The strategy of active disturbance rejection control (ADRC), which can automatically estimate and compensate for the total disturbance of the system in real-time, is introduced into the rotor-side converter to mitigate the SSCI in the DFIG. ADRC is designed based on dynamic parameter tuning and chaos optimization. Finally, a detailed model-based time-domain simulation is conducted to evaluate the performance of the proposed optimized ADRC (O-ADRC) compared to conventional virtual impedance and ADRC. The simulation results show that O-ADRC can effectively mitigate the SSCI under different operating conditions and provide sufficient damping for the DFIG-based wind farms.
5Â citations
TL;DR: Subsynchronous resonance (SSR) instability was accurately analyzed in doubly fed induction generator (DFIG)-based wind farms by the linearization of equations and modal analysis and the participation factor was shown to be the capacitor series voltage of the line, considered an input signal to the SSRPC.
Abstract: In this paper, subsynchronous resonance (SSR) instability was accurately analyzed in doubly fed induction generator (DFIG)-based wind farms by the linearization of equations and modal analysis. In addition, the possibility of high compensation for the transmission lines connected to DFIG-based wind farms was provided using a SSR prevention controller (SSRPC). For this purpose, an SSRPC was connected to the output voltage of the grid side converter (GSC) of the DFIG. The GSC output voltage was selected as the connection point of the SSRPC because it directly affects the induction generator effect (IGE) and can be an inhibitor factor in its occurrence. Furthermore, using system dynamic equations and the participation factor, it was shown that the effective factor on subsynchronous mode was the capacitor series voltage of the line, considered an input signal to the SSRPC. To validate the performance of the proposed method, a simulation was performed based on the IEEE SSR first benchmark model using the software MATLAB/Simulink.
4Â citations
References
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Book•
01 Jan 1994
TL;DR: In this article, the authors present a model for the power system stability problem in modern power systems based on Synchronous Machine Theory and Modelling, and a model representation of the synchronous machine representation in stability studies.
Abstract: Part I: Characteristics of Modern Power Systems. Introduction to the Power System Stability Problem. Part II: Synchronous Machine Theory and Modelling. Synchronous Machine Parameters. Synchronous Machine Representation in Stability Studies. AC Transmission. Power System Loads. Excitation in Stability Studies. Prime Mover and Energy Supply Systems. High-Voltage Direct-Current Transmission. Control of Active Power and Reactive Power. Part III: Small Signal Stability. Transient Stability. Voltage Stability. Subsynchronous Machine Representation in Stability Studies. AC Transmission. Power System Loads. Excitation in Stability Studies. Prime Mover and Energy Supply Systems, High-Voltage Direct-Current Transmission. Control of Active Power and Reactive Power. Part III: Small Signal Stability. Transient Stability. Voltage Stability. Subsynchronous Oscillations. Mid-Term and Long-Term Stability. Methods of Improving System Stability.
13,467Â citations
TL;DR: In this article, a dynamic model is developed to analyze the induction generator effect (IGE) and torsional interaction (TI) in a doubly-fed induction generator (DFIG)-based wind farms interconnected with series compensated networks.
Abstract: This paper conducts an analysis of subsynchronous resonance (SSR) phenomena in doubly-fed induction generator (DFIG)-based wind farms interconnected with series compensated networks. A dynamic model is developed to analyze the induction generator effect (IGE) and torsional interaction (TI) in such systems. A test system derived from the IEEE first benchmark model is considered for the analysis. The effect of two factors namely: 1) series compensation level and 2) wind speed on the IGE and TI are studied. In addition, impact of the inner current converter controller parameters and turbine parameters on SSR is also addressed. Small signal (eigenvalue) analysis is conducted to assess the damping of network and torsional modes followed by dynamic (time domain) simulations. The major contribution of this paper is the analytical investigation on SSR phenomena presented in DFIG-based wind farms interconnected with series compensated networks. The paper clearly demonstrates that IGE instead of TI is the major reason for SSR in such systems.
407Â citations
TL;DR: In this paper, a static var compensator (SVC) with a simple voltage regulator is employed at the induction-generator (IG) terminal in addition to the fixed shunt capacitor for dynamic reactive power support.
Abstract: The rapid growth of wind power systems worldwide will likely see the integration of large wind farms with electrical networks that are series compensated for ensuring stable transmission of bulk power. This may potentially lead to subsynchronous-resonance (SSR) issues. Although SSR is a well-understood phenomenon that can be mitigated with flexible ac transmission system (FACTS) devices, scant information is available on the SSR problem in a series-compensated wind farm. This paper reports the potential occurrence and mitigation of SSR caused by an induction-generator (IG) effect as well as torsional interactions, in a series-compensated wind farm. SSR suppression is achieved as an additional advantage of FACTS controllers which may already be installed in the power system for achieving other objectives. In this study, a wind farm employing a self-excited induction generator is connected to the grid through a series-compensated line. A static var compensator (SVC) with a simple voltage regulator is first employed at the IG terminal in addition to the fixed shunt capacitor for dynamic reactive power support. The same SVC is shown to effectively damp SSR when equipped with an SSR damping controller. Also, a thyristor-controlled series capacitor (TCSC) that is actually installed to increase the power transfer capability of the transmission line is also shown to damp subsynchronous oscillations when provided with closed-loop current control. While both FACTS controllers-the SVC and TCSC-can effectively mitigate SSR, the performance of TCSC is shown to be superior. Extensive simulations have been carried out using EMTDC/PSCAD to validate the performance of SVC and TCSC in damping SSR.
296Â citations
Book•
31 Oct 1998TL;DR: In this article, the authors present an analysis of the effect of torsional oscillations in parallel-connected turbine generators on the performance of the generator and the generator's mechanical system.
Abstract: 1. Introduction.- 1.1 General.- 1.2 Definitions of SSR.- 1.3 Interactions with power system controllers.- 1.4 FACTS Controllers.- 1.5 Methods of Analysis of SSR.- 1.6 Chapter outline.- 2. Modelling of Turbine Generator.- 2.1 Introduction.- 2.2 Synchronous machine model.- 2.3 Park's transformation.- 2.4 Per unit quantities.- 2.5 Operational impedances and equivalent circuits.- 2.6 Modelling of excitation control system.- 2.7 Modelling of turbine generator mechanical system.- 2.8 Modelling of turbine and governor.- 2.9 Modelling and analysis of the mechanical and prime mover system.- 2.10 Synchronous generator modelling for transient simulation.- 3. Modelling of the Electric Network.- 3.1 Introduction.- 3.2 Transmission lines.- 3.3 Transformation using ? - ? variables.- 3.4 State equations.- 3.5 Interface between the network and generator.- 3.6 Impedance functions.- 3.7 Simulation of electromagnetic transients.- 4. Analysis of SSR with Fixed Series Compensation.- 4.1 Introduction.- 4.2 Analysis of induction generator effect: frequency scanning method.- 4.3 Analysis of torsional interaction(TI).- 4.4 State equations and eigenvalue analysis.- 4.5 An algorithm for computing torsional modes.- 4.6 Countermeasures for SSR.- 4.7 Torsional oscillations in parallel connected turbine generators.- 5. Interactions with Power System Stabilizer.- 5.1 Introduction.- 5.2 Basic concept in the application of PSS.- 5.3 Design of PSS.- 5.4 Torsional interaction with PSS.- 5.5 A case study.- 6. Interactions with HVDC Converter Control.- 6.1 Introduction.- 6.2 HVDC converters and control.- 6.3 Modelling of HVDC system for study of torsional interactions.- 6.4 Analysis of torsional interactions - A simplified approach.- 6.5 A case study.- 6.6 A simplified damping torque analysis.- 6.7 Control of torsional interaction.- 7. Interactions with Shunt Compensators.- 7.1 Introduction.- 7.2 Static Var Compensator.- 7.3 Torsional Interactions with SVC.- 7.4 Static Condenser(STATCON).- 7.5 Torsional interactions with STATCON.- 7.6 A simplified analysis of torsional interaction with voltage controller.- 8. Interactions with Series Compensators.- 8.1 Introduction.- 8.2 Thyristor Controlled Series Compensator.- 8.3 Modelling of TCSC for SSR studies.- 8.4 Mitigation of SSR with TCSC.- 8.5 Static Synchronous Series Compensator (SSSC).- 8.6 Torsional interactions with SSSC.- Appendices.- A- Data on IEEE Benchmark Models.- A.1 IEEE First Benchmark Model ( FBM ).- A.2 IEEE Second Benchmark Model ( SBM ).- B- Calculation of Initial Conditions.- C- Abbreviations.- References and Bibliography.
283Â citations