Nupur Rathore

Bio: Nupur Rathore is an academic researcher from Indian Institute of Technology, Jodhpur. The author has contributed to research in topics: Converters & Sliding mode control. The author has an hindex of 4, co-authored 9 publications receiving 40 citations.

Mitigation of Negative Impedance Instabilities in a DC/DC Buck-Boost Converter with Composite Load

Abstract: A controller to mitigate the destabilizing effect of constant power load (CPL) is proposed for a DC/DC buck–boost converter. The load profile has been considered to be predominantly of CPL type. The negative incremental resistance of the CPL tends to destabilize the feeder system, which may be an input filter or another DC/DC converter. The proposed sliding mode controller aims to ensure system stability under the dominance of CPL. The effectiveness of the controller has been validated through real-time simulation studies and experiments under various operating conditions. The controller has been demonstrated to be robust with respect to variations in supply voltage and load and capable of mitigating instabilities induced by CPL. Furthermore, the controller has been validated using all possible load profiles, which may arise in modern-day DC-distributed power systems.

ISMC for Boost-Derived DC–DC–AC Converter: Mitigation of $2\omega$ -Ripple and Uncertainty, and Improvement in Dynamic Performance

Abstract: In controller design, the classical control techniques have their distinct advantages and capabilities. The integral sliding-mode control (ISMC) leverages the merits of such control techniques by allowing their merger with the sliding-mode control (SMC). ISMC is composed of two components, a nominal control designed using any methodology and a discontinuous-SMC, and thus the system can have specified performance with high degree of robustness. The proposed work achieves multiple objectives, i.e., mitigates $2\omega$ -ripple, ensures robustness, and improves dynamic performance. The proposed ISM-based controller amalgamates SMC with a new dual-loop adaptive PID-control (as the nominal control). The discontinuous-SMC part ensures robustness against the matched-uncertainty, i.e., disturbances entering through the input channel such as parametric variations, exogenous disturbances, modeling-error, and the nominal control mitigate $2\omega$ -ripple at the input of dc–dc–ac converter. Moreover, the adaptive nature of nominal control improves the system performance at the large line-load transients unlike the conventional control. Furthermore, the proposed controller supports the reduction of $2\omega$ -ripple at the input of converter. The proposed control scheme is validated using 1-kW prototype.

Emulation of Loss Free Resistor for Single-Stage Three-Phase PFC Converter in Electric Vehicle Charging Application

Abstract: In this article, the modular three-phase ac–dc converter using single-phase isolated C uk rectifier modules for charging of electric vehicles is discussed. The converters are designed and analyzed for the continuous conduction mode (CCM). This article is based on a new concept of adaptive sliding-mode-based loss-free resistor (ASLFR). ASLFR is a control scheme, which allows dual aim of power factor correction along with tight voltage regulation; hence, the adopted topology serves as a fitting single-stage solution for balanced three-phase systems. Complete theory is developed for the application, and the effectiveness of the scheme is well-established. Various studies to confirm the robustness of the system to any load and line variation are carried out. Moreover, a qualitative analysis is also made to show the expediency of the proposed ASLFR. Simulation as well as experimental studies are claimed theoretically.

Adaptive Sliding Mode Based Loss-Free Resistor for Power-Factor Correction Application

Abstract: The emulation of virtual resistance finds various applications in the power processing industry. This paper proposes a novel notion of adaptive sliding mode based loss free resistor (ASLFR). This is achieved by allowing the input power of the power-out power-in ( POPI ) system to vary, in order to accommodate the load demands. In this paper, the concept is illustrated for power-factor correction (PFC) applications. The ASLFR is used to achieve the dual purpose of harmonics-free rectification along with excellent system response under load and line transients. The scheme serves itself as an efficient single-stage PFC solution. A generic mathematical formulation of the scheme is presented, which can be used for different converters. Then on, a boost topology, operating in continuous conduction mode, is chosen to demonstrate theoretical developments and to showcase the effectiveness of the scheme. The robustness of the proposed controller to any line or load variation is established. A fast voltage recovery with almost no undershoot/overshoot is achieved at transients by using the proposed controller. Additionally, a qualitative analysis is provided to demonstrate the expediency of the proposed ASLFR. The theoretical claims are well supported by simulation as well as experimental results.

Constant power loads (CPL) with microgrids: problem definition, stability analysis and compensation techniques

Abstract: This paper provides a comprehensive review of the major concepts associated with the μgrid, such as constant power load (CPL), incremental negative resistance or impedance (INR/I) and its dynamic behaviours on the μgrid, and power system distribution (PSD). In general, a μgrid is defined as a cluster of different types of electrical loads and renewable energy sources (distributed generations) under a unified controller within a certain local area. It is considered a perfect solution to integrate renewable energy sources with loads as well as with a traditional grid. In addition, it can operate with a conventional grid, for example, by energy sourcing or a controllable load, or it can operate alone as an islanding mode to feed required electric energy to a grid. Hence, one of the important issues regarding the μgrid is the constant power load that results from the tightly designed control when it is applied to power electronic converters. The effect of CPL is incremental negative resistance that impacts the power quality of a power system and makes it at negative damping. Also, in this paper, a comprehensive study on major control and compensation techniques for μgrid has been included to face the instability effects of constant power loads. Finally, the merits and limitations of the compensation techniques are discussed.

Control Strategies and Power Decoupling Topologies to Mitigate 2ω-Ripple in Single-Phase Inverters: A Review and Open Challenges

Abstract: This paper provides a comprehensive review of the control approaches and the power-decoupling topologies to mitigate 2ω-ripple problem in the single-phase inverters, its solutions, and discusses open challenges yet to be addressed. The cause and effects of 2ω-ripple problem and its solution based on the passive and active power-decoupling techniques are discussed. A subcategory of the active power-decoupling technique nominated as the control-oriented compensation technique is reviewed in detail, this technique can achieve the ripple-mitigation at the source through the control but not necessarily adds extra circuit or active filter to the system. The control-oriented compensation techniques can be applied in the two-stage DC-DC-AC converters and the single-stage inverters having a front-end control capability with the H-bridge such as in the quasi-switched-boost inverters. The merits and associated challenges of these techniques are listed and summarized in a tabular form. Finally, a conclusive discussion with open challenges is presented.

Voltage Regulation in Buck–Boost Converters Feeding an Unknown Constant Power Load: An Adaptive Passivity-Based Control

Abstract: Rapid developments in power distribution systems and renewable energy have widened the applications of dc–dc buck–boost converters in dc voltage regulation. Applications include vehicular power systems, renewable energy sources that generate power at a low voltage, and dc microgrids. It is noted that the cascade connection of converters in these applications may cause instability due to the fact that converters acting as loads have a constant power load (CPL) behavior. In this brief, the output voltage regulation problem of a buck–boost converter feeding a CPL is addressed. The construction of the feedback controller is based on the interconnection and damping assignment control technique. In addition, an immersion and invariance parameter estimator is proposed to compute online the extracted load power, which is difficult to measure in practical applications. It is ensured through the design that the desired operating point is (locally) asymptotically stable with a guaranteed domain of attraction. The approach is validated via computer simulations and experimental prototyping.