Rajiv K. Varma

Bio: Rajiv K. Varma is an academic researcher from University of Western Ontario. The author has contributed to research in topics: Photovoltaic system & Electric power system. The author has an hindex of 31, co-authored 150 publications receiving 4995 citations. Previous affiliations of Rajiv K. Varma include Indian Institutes of Technology & Indian Institute of Technology Kanpur.

Modal analysis of Type-1 wind farm connected to series compensated transmission line and LCC HVDC transmission line

Abstract: This papers presents a comprehensive analysis of the potential of sub-synchronous resonance (SSR) in Type-1 wind farms connected to Line Commutated Converter (LCC) based HVDC transmission line. Since series compensated lines are also known to cause induction generator effect SSR in Type 1 wind turbine generators, this paper also considers a series compensated line in parallel with the HVDC line for the investigation of potential SSR. CIGRE Benchmark HVDC system and IEEE First Benchmark system are considered as the study system components. A dynamic model of the study system is developed and linearized at several operating points for eigenvalue analysis of the potential of SSR. A sensitivity study of the SSR modes with respective to variation in different model parameter such as rectifier firing angle, DC line power flow, series compensation level is also reported. It is found that HVDC rectifier station current regulator does not interact with any sub-synchronous modes of the wind turbine generator. Hence, the operation of a Type-1 wind farm connected to series compensated line and HVDC line is may not be subject to SSR issues. However, when the wind farm operates radially with the series compensated line, it may experience SSR oscillation due to induction generator effect.

New Static Var Compensator (SVC) based damping control using remote generator speed signal

Abstract: Rapid advances in Wide-Area Measurement (WAM) and communication technologies have made the use of remote system data/signals for effective control and operation of power systems possible. This paper presents a new concept of damping control of Static Var Compensator (SVC) based on rotor speeds of remotely located generators. The concept is demonstrated in three study systems: a single machine infinite bus system, a two-area four-machine 11-bus system, and the Western System Coordinating Council (WSCC) three-machine nine-bus meshed system. The performance of the proposed remote generator speed signal is compared with the traditionally utilised local signals for SVC damping control through nonlinear time domain simulations. It is shown that the rotor speed of the remotely located generator that significantly participates in the lightly or negatively damped electromechanical mode of oscillation is the most effective SVC control signal in damping electromechanical oscillations in a power system.

Bibliography of HVDC 2004-2005 IEEE working group report

Abstract: This paper presents a bibliography of HVDC transmission technology for the year 2004-2005. It provides a listing of various journal and conference papers in this area.

A method to determine closest Hopf bifurcation in power systems considering exciter and load dynamics

Abstract: Saddle-node and Hopf bifurcations have been recognized as the reasons behind power system voltage instability. In general, Hopf bifurcation is found to occur well before the saddle-node bifurcation under system parameter variation. This paper presents a method to determine the closest Hopf bifurcation from the given operating point considering generator, exciter and load dynamics. The closest distance has been computed in load parameter space using an optimization based model. Results obtained on a sample power system network reveals that the stability margin computed with respect to the Hopf bifurcation further shrinks when load dynamics is considered.

Bibliography of HVDC transmission: 1998 IEEE Working Group report

Abstract: This paper presents a Bibliography of High Voltage Direct Current (HVDC) transmission technology for 2009-2010. It provides a listing of various journal and conference papers in this area. This Bibliography includes papers published until November 2011. If this paper is granted revise and resubmit status, the Working Group will update this bibliography to include all papers published till the end of year 2011 and make it more complete.

VSC-Based HVDC Power Transmission Systems: An Overview

Abstract: The ever increasing progress of high-voltage high-power fully controlled semiconductor technology continues to have a significant impact on the development of advanced power electronic apparatus used to support optimized operations and efficient management of electrical grids, which, in many cases, are fully or partially deregulated networks. Developments advance both the HVDC power transmission and the flexible ac transmission system technologies. In this paper, an overview of the recent advances in the area of voltage-source converter (VSC) HVdc technology is provided. Selected key multilevel converter topologies are presented. Control and modeling methods are discussed. A list of VSC-based HVdc installations worldwide is included. It is confirmed that the continuous development of power electronics presents cost-effective opportunities for the utilities to exploit, and HVdc remains a key technology. In particular, VSC-HVdc can address not only conventional network issues such as bulk power transmission, asynchronous network interconnections, back-to-back ac system linking, and voltage/stability support to mention a few, but also niche markets such as the integration of large-scale renewable energy sources with the grid and most recently large onshore/offshore wind farms.

Energy function analysis for power system stability

Abstract: (1990). ENERGY FUNCTION ANALYSIS FOR POWER SYSTEM STABILITY. Electric Machines & Power Systems: Vol. 18, No. 2, pp. 209-210.

Thyristor-Based Facts Controllers for Electrical Transmission Systems

Abstract: 1. Introduction. 1.1 Background. 1.2 Electrical Transmission Networks. 1.3 Conventional Control Mechanisms. 1.4 Flexible ac Transmission Systems (FACTS). 1.5 Emerging Transmission Networks. 2. Reactor--Power Control in Electrical Power Transmission Systems. 2.1 Reacrive Power. 2.2 Uncompensated Transmission Lines. 2.3 Passive Compensation. 2.4 Summary. 3. Principles of Conventional Reactive--Power Compensators. 3.1 Introduction. 3.2 Synchronous Condensers. 3.3 The Saturated Reactor (SR). 3.4 The Thyristor--Controlled Reactor (TCR). 3.5 The Thyristor--Controlled Transformer (TCT). 3.6 The Fixed Capacitor--Thyristor--Controlled Reactor (FC--TCR). 3.7 The Mechanically Switched Capacitor--Thristor--Controlled Reactor (MSC--TCR). 3.8 The Thyristor--Switched capacitor and Reactor. 3.9 The Thyristor--Switched capacitor--Thyristor--Controlled Reactor (TSC--TCR). 3.10 A Comparison of Different SVCs. 3.11 Summary. 4. SVC Control Components and Models. 4.1 Introduction 4.2 Measurement Systems. 4.3 The Voltage Regulator. 4.4 Gate--Pulse Generation. 4.5 The Synchronizing System. 4.6 Additional Control and Protection Functions. 4.7 Modeling of SVC for Power--System Studies. 4.8 Summary. 5. Conceepts of SVC Voltage Control. 5.1 Introduction 5.2 Voltage Control. 5.3 Effect of Network Resonances on the Controller Response. 5.4 The 2nd Harmonic Interaction Between the SVC and ac Network. 5.5 Application of the SVC to Series--Compensated ac Systems. 5.6 3rd Harmonic Distortion. 5.7 Voltage--Controlled Design Studies. 5.8 Summary. 6. Applications. 6.1 Introduction. 6.2 Increase in Steady--State Power--Transfer Capacity. 6.3 Enhancement of Transient Stability. 6.4 Augmentation of Power--System Damping. 6.5 SVC Mitigation of Subsychronous Resonance (SSR). 6.6 Prevention of Voltage Instability. 6.7 Improvement of HVDC Link Performance. 6.8 Summary. 7. The Thyristor--Controlled SeriesCapacitor (TCSC). 7.1 Series Compensation. 7.2 The TCSC Controller. 7.3 Operation of the TCSC. 7.4 The TSSC. 7.5 Analysis of the TCSC. 7.6 Capability Characteristics. 7.7 Harmonic Performance. 7.8 Losses. 7.9 Response of the TCSC. 7.10 Modeling of the TCSC. 7.11 Summary. 8. TCSC Applications. 8.1 Introduction. 8.2 Open--Loop Control. 8.3 Closed--Loop Control. 8.4 Improvement of the System--Stability Limit. 8.5 Enhancement of System Damping. 8.6 Subsynchronous Resonanace (SSR) Mitigation. 8.7 Voltage--Collapse Prevention. 8.8 TCSC Installations. 8.9 Summary. 9. Coordination of FACTS Controllers. 9.1 Introduction 9.2 Controller Interactions. 9.3 SVC--SVC Interaction. 9.4 SVC--HVDC Interaction. 9.5 SVC--TCSC Interaction. 9.6 TCSC--TCSC Interaction. 9.7 Performance Criteria for Damping--Controller Design. 9.8 Coordination of Multiple Controllers Using Linear--Control Techniques. 9.9 Coordination of Multiple Controllers using Nonlinear--Control Techniques. 9.10 Summary. 10. Emerging FACTS Controllers. 10.1 Introduction. 10.2 The STATCOM. 10.3 THE SSSC. 10.4 The UPFC. 10.5 Comparative Evaluation of Different FACTS Controllers. 10.6 Future Direction of FACTS Technology. 10.7 Summary. Appendix A. Design of an SVC Voltage Regulator. A.1 Study System. A.2 Method of System Gain. A.3 Elgen Value Analysis. A.4 Simulator Studies. A.5 A Comparison of Physical Simulator results With Analytical and Digital Simulator Results Using Linearized Models. Appendix B. Transient--Stability Enhancement in a Midpoint SVC--Compensated SMIB System. Appendix C. Approximate Multimodal decomposition Method for the Design of FACTS Controllers. C.1 Introduction. C.2 Modal Analysis of the ith Swing Mode, C.3 Implications of Different Transfer Functions. C.4 Design of the Damping Controller. Appendix D. FACTS Terms and Definitions. Index.

Modular Multilevel Converters for HVDC Applications: Review on Converter Cells and Functionalities

Abstract: In this paper, the principle of modularity is used to derive the different multilevel voltage and current source converter topologies. The paper is primarily focused on high-power applications and specifically on high-voltage dc systems. The derived converter cells are treated as building blocks and are contributing to the modularity of the system. By combining the different building blocks, i.e., the converter cells, a variety of voltage and current source modular multilevel converter topologies are derived and thoroughly discussed. Furthermore, by applying the modularity principle at the system level, various types of high-power converters are introduced. The modularity of the multilevel converters is studied in depth, and the challenges as well as the opportunities for high-power applications are illustrated.

Damping controller design for power system oscillations using global signals

Abstract: This paper describes a new power system stabilizer (PSS) design for damping power system oscillations focusing on interarea modes. The input to the PSS consists of two signals. The first signal is mainly to damp the local mode in the area where PSS is located using the generator rotor speed as an input signal. The second is an additional global signal for damping interarea modes. Two global signals are suggested; the tie-line active power and speed difference signals. The choice of PSS location, input signals and tuning is based on modal analysis and frequency response information. These two signals can also be used to enhance damping of interarea modes using SVC located in the middle of the transmission circuit connecting the two oscillating groups. The effectiveness and robustness of the new design are tested on a 19-generator system having characteristics and structure similar to the Western North American grid.