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.

Static and dynamic analysis of homogeneous Micropolar-Cosserat panels

Abstract: This paper communicates an analytical study on computing the natural frequencies and in-plane deflections caused by static forces in the panel walls using Euler-Bernoulli, Timoshenko, Timoshenko an...

Instability in induction generator based wind farms connected to series compensated transmission lines

Abstract: This paper presents a study of subsynchronous mode instability in Induction Generator (IG) based wind farm connected to a series compensated transmission line. The IEEE First SSR benchmark system is modified by replacing the synchronous generator with an aggregated wind farm. A small signal stability analysis is carried out to detect the instability analytically and then results are validated through a detailed electromagnetic transient simulation using PSCAD/EMTDC. Two types of studies are performed for the small signal analysis. First, a linearized state space model is developed for the eigenvalue calculation. Then, a simple equivalent circuit model is developed for the resonant speed analysis. From the equivalent circuit model, two resonant speeds - upper resonant speed (URS) and lower resonant speed (LRS), are obtained. If the post fault speed of the aggregated generator comes close or enters in the band within these two resonant speeds, the induction generator may become unstable. The performance of the aggregated wind farm model is validated with a distributed wind farm model. It is shown that the wind generator may experience SSR if the fault occurs at the terminals of the wind farm even at a realistic level of series compensation.

Bibliography of FACTS: 2000 — Part II IEEE working group report

Abstract: This paper presents the second part of the Bibliography of FACTS technology mainly for the year 2000. Papers published/presented in Conferences in later part of 1999, which appeared on search engines only in the year 2000 are also included in this Bibliography. It provides a listing of various journal and conference papers in this area.

Determination of Suitable Locations for Shunt Compensators in Multi-Machine Power Systems: A Systematic Approach

Abstract: With the widespread and active consideration of installation of flexible AC transmission systems (FACTS) controllers for better controllability in a power grid, appropriate placement of these devices is becoming increasingly important. Improperly placed FACTS controllers fail to give the optimum performance and, in some cases, can even be counterproductive. As FACTS controllers are expected to maintain stability and security margin in a system for high power transfer level, proper placement strategies of these devices must be examined from different stability considerations; i.e., voltage stability, small signal stability, and transient stability. In this paper, a strategy for placement of shunt compensators has been proposed based on a combined consideration of voltage stability and small signal stability for a moderately large multimachine power system. The results are also validated with the help of electromagnetic transient simulation.

Operational experience with Static var Compensators in Ontario, Canada

Abstract: This paper presents the operational experiences with the different Static VAr Compensators (SVCs) in Ontario, Canada. All these SVCs were installed as a part of long term transmission development plan to facilitate addition of new renewable generation and implementation of supply mix policy in Ontario. This paper intends to bring out important lessons learned with the SVCs for the benefit of power engineering community.

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.