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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.


Papers
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Proceedings ArticleDOI
01 Aug 2018
TL;DR: A novel smart inverter PV-STATCOM with a response time of 1–2 cycles can provide an equivalent service as an actual STATCOM in a given application and possibly seek revenues for providing this service.
Abstract: This paper presents a novel smart inverter PV-STATCOM in which a PV inverter can be controlled as a dynamic reactive power compensator - STATCOM. The proposed PV-STATCOM can be utilized to provide voltage control during critical system needs on a 24/7 basis. In the nighttime, the entire inverter capacity is utilized for STATCOM operation. During a critical system disturbance in the daytime, the smart inverter discontinues its real power generation function temporarily (for about a few seconds), and releases its entire inverter capacity for STATCOM operation. Once the disturbance is cleared and the need for grid voltage control is fulfilled, the solar farm returns to its pre-disturbance real power production. The Low Voltage Ride Through (LVRT) performance of the PVSTATCOM is demonstrated through both EMTDC/PSCAD simulations and laboratory implementation using dSPACE control. This proposed PV-STATCOM with a response time of 1-2 cycles, can provide an equivalent service as an actual STATCOM in a given application and possibly seek revenues for providing this service.

36 citations

Proceedings ArticleDOI
25 Jun 2012
TL;DR: In this article, the impact of large-scale penetration of distributed generation (DG) system in the presence of non-linear loads on the grid side current harmonics is examined.
Abstract: In this paper, the impact of large-scale penetration of distributed generation (DG) system in the presence of non-linear loads is addressed. The effect of different DG penetration levels on the grid side current harmonics is examined. It is found that current harmonics generated by downstream non-linear loads with a TDD (total demand distortion) that is compliant with IEEE Standards can lead to significantly high THD (total harmonic distortion) values at the grid side under certain loading scenarios. These low magnitude highly distorted currents may cause protection circuitry and grid-synchronizing circuitry malfunctioning, and may even cause a resonance condition with power factor correction capacitor on the network. This paper further presents a control application of Photovoltaic (PV) solar plant based DG inverter o mitigate the above harmonics problem. The increased harmonic level issue and the application of PV solar plant to mitigate such problem have been demonstrated both by MATLAB/ SIMULINK simulation studies and laboratory experimental results.

35 citations

Journal ArticleDOI
17 Aug 2016
TL;DR: In this paper, the slope of a PV inverter current is used to predict if the current is expected to exceed its rated value due to any grid faults, which can be used to rapidly and autonomously transform the PV solar farm into a dynamic reactive power compensator STATCOM (termed PV-STATCOM) for providing voltage support function.
Abstract: This paper proposes a new fast technique, in which the slope of a photovoltaic (PV) inverter current is utilized to predict if the current is expected to exceed its rated value due to any grid faults. Two applications of this technique are demonstrated. In jurisdictions where grid codes require distributed generators (DGs) to disconnect after a fault occurrence, such as in Ontario, Canada, this technique is utilized to rapidly disconnect the PV solar system even before the inverter short circuit current actually exceeds the rated current of the inverter, thereby obviating the problem of any adverse short circuit current contribution into the grid. However, in regions where grid codes require DGs to stay connected and provide grid support, such as low-voltage ride through, this technique can be used to rapidly and autonomously transform the PV solar farm into a dynamic reactive power compensator STATCOM (termed PV-STATCOM) for providing voltage support function. In this paper, the PV-STATCOM is used to stabilize a critical induction motor load in the vicinity of the solar farm, which would have otherwise become unstable due to the grid fault. PSCAD-based simulation studies are performed on a realistic distribution network to demonstrate the effectiveness of this technique.

35 citations

Proceedings ArticleDOI
01 Oct 2012
TL;DR: In this paper, a real-time digital simulation study of a PV solar system as a STATCOM (PV-STATCOM) on RTDS (Real Time Digital Simulator) in a unique state-of-the-art research laboratory in a utility premise is presented.
Abstract: This paper presents a real-time digital simulation study of a PV solar system as a STATCOM (PV-STATCOM) on RTDS (Real Time Digital Simulator) in a unique state-of-the-art research laboratory in a utility premise. This PV-STATCOM technology is utilized in the night for power factor correction and voltage regulation at the terminals of an induction motor operating at poor power factor. During daytime, the same objectives will be accomplished together with production of real power from solar insolation, by utilizing the inverter capacity remaining after real power generation. The local distribution company London Hydro is implementing this new technology, for the first time in Canada, on a 10 kW solar system to be installed on the rooftop of their headquarters building in Fall 2012. The proposed new control on PV solar system will help increase the utilization of the PV solar system, improve overall electrical system performance and provide a potential of additional revenue earning for solar farms for providing the above services, both during night and day.

35 citations

Proceedings ArticleDOI
24 Jul 2011
TL;DR: In this paper, the authors present the Bibliography of Flexible AC Transmission System (FACTS) applications for grid integration of wind power systems and PV solar power systems during the period 1995 to 2010.
Abstract: This paper presents the Bibliography of Flexible AC Transmission System (FACTS) applications for grid integration of wind power systems and PV solar power systems during the period 1995 to 2010. It provides a listing of various journal and conference papers in this area.

35 citations


Cited by
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Journal ArticleDOI
TL;DR: An overview of the recent advances in the area of voltage-source converter (VSC) HVdc technology is provided in this paper, where a list of VSC-based HVDC installations worldwide is included.
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.

2,023 citations

Journal ArticleDOI
TL;DR: In this paper, the authors present an energy fundiment analysis for power system stability, focusing on the reliability of the power system and its reliability in terms of power system performance and reliability.
Abstract: (1990). ENERGY FUNCTION ANALYSIS FOR POWER SYSTEM STABILITY. Electric Machines & Power Systems: Vol. 18, No. 2, pp. 209-210.

1,080 citations

Book
27 Feb 2002
TL;DR: In this paper, the authors present a comparison of different SVC controllers for power transmission networks with respect to their performance in terms of the number of SVC inputs and outputs, as well as the frequency of the SVC outputs.
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.

954 citations

Journal ArticleDOI
TL;DR: In this article, the principle of modularity is used to derive the different multilevel voltage and current source converter topologies for high-power dc systems, where the derived converter cells are treated as building blocks and are contributing to the modularity of the system.
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.

883 citations

Journal ArticleDOI
01 May 1996
TL;DR: In this paper, a new power system stabilizer (PSS) design for damping power system oscillations focusing on inter-area modes is described, and two global signals are suggested; the tie-line active power and speed difference 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.

523 citations