Fulwani, Deepak M

The study proposes a method to design a non-linear sliding surface to achieve better transient response for a class of single-input and single-output (SISO) non-linear uncertain system represented in a Brunowsky canonical form. The proposed surface can also be used for linear uncertain systems with matched perturbations. The proposed surface increases the damping ratio of the closed-loop system from its initial low value; as the output approaches the setpoint from its initial value. Initially, the system is lightly damped resulting in a quick response and as the output approaches the setpoint, the system is overdamped to avoid overshoot. The existence of sliding mode is proved and a new control law is proposed to enforce sliding motion. The scheme is able to achieve low overshoot and short settling time simultaneously which is not possible with a linear sliding surface. To ease the synthesis of the non-linear surface, linear matrix inequalities-based algorithm is proposed. Effectiveness of the proposed scheme is illustrated by the simulation results. © 2011 The Institution of Engineering and Technology.

A class of nonlinear uncertain systems with saturated actuator is considered in this paper. Sliding surface matrix is obtained using parameterized Riccatti equation. The proposed surface ensures that control limits are respected in a region of state space. This region can be made sufficiently large by choosing appropriate value of design parameters. © 2012 IEEE.

The switched boost inverters are single stage topologies that boost dc voltage and convert it to required ac voltage. It requires lesser number of components and is more efficient compared to conventional two stage dc-dc-ac methods. The dc-ac conversion results in second order harmonic currents (SHCs) to be reflected at the source end. It causes various problems such as heating or failure of sources, oscillations in maximum power point tracking. The active or passive filters for SHCs may increase component count as well as increase overall cost of the system. In this paper, a sliding mode control based voltage and current control method method is proposed so as to reduce the SHCs in Switched Boost Inverter (SBI). Also, the transients during dc or ac load variations are kept within allowed range. This results in excellent voltage regulation during load changes. The proposed controller is validated through simulation for different types of load and upto 50 % load variations.

Distributed control of converters is important to achieve plug and play functionality in a dc microgrid. It must ensure proportional load sharing among converters and voltage regulation of the dc bus. Droop control is a conventional distributed control method to achieve load sharing among converters in a dc microgrid. It is realized by reducing the voltage reference, linearly or dynamically, as the load increases. This degrades the voltage regulation as the overall bus voltage decreases as the load increases. In this paper, a sliding mode control based adaptive voltage tuning method is proposed such that the voltage reference is adjusted dynamically above and below the desired dc bus voltage to achieve load sharing. This results in excellent voltage regulation, also the proposed control is realized locally hence it facilitates plug and play functionality. The per unit input current value is exchanged among the neighboring converters. The proposed controller is validated through simulation.

The single-stage DC–AC converters are capable of boosting the DC voltage and conversion to AC by incorporating the shoot-through state between the dead time intervals of traditional inverters. However, these suffer from second-order voltage and current reflections at the DC input side. The paper proposes a sliding mode control (SMC) based control of single-stage inverters. The proposed control is used to reduce second-order ripples currents (SRCs) by inductor impedance shaping which significantly reduces SRC propagation to the source. This improves the life span of source and converter components without any external ripple reduction circuitry. The proposed methodology is applied to two topologies-Quasi-ZSI, and Embedded Switched Boost Inverter. The proposed method is verified by simulation and experimentation.

This paper performs an extensive review on control schemes and architectures applied to dc microgrids (MGs). It covers multilayer hierarchical control schemes, coordinated control strategies, plug-and-play operations, stability and active damping aspects, as well as nonlinear control algorithms. Islanding detection, protection, and MG clusters control are also briefly summarized. All the mentioned issues are discussed with the goal of providing control design guidelines for dc MGs. The future research challenges, from the authors' point of view, are also provided in the final concluding part.

This article presents emulation of a programmable power electronic, constant power load (CPL) using a dc/dc step-up (boost) converter. The converter is controlled by a robust sliding mode controller (SMC). A novel switching surface is proposed to ensure a required power sunk by the converter. The proposed dc CPL is simple in design, has fast dynamic response and high accuracy, and offers an inexpensive alternative to study converters for cascaded dc distribution power system applications. Furthermore, the proposed CPL is sufficiently robust against the input voltage variations. A laboratory prototype of the proposed dc CPL has been developed and validated with SMC realised through OPAL-RT platform. The capability of the proposed dc CPL is confirmed via experimentations in varied scenarios.

Single-phase inverter suffers an unwanted second-order ripple at DC input of it. A substantial amount of this ripple may propagate through the system components and inject into the DC source. This causes several problems; related to system efficiency, life, cost, size, reliability and stability. This paper proposes an adaptive non-linear sliding mode controller for quasi-switched boost inverter used mainly in microinverter applications. The proposed controller shapes the output-impedance of the boost circuit of quasi-switched boost inverter such that the propagation of the ripple to DC source is resisted. The proposed control technique is verified using Matlab-Simulink.

This paper proposes a novel notion of Adaptive Sliding mode based loss free resistor (ASLFR), to achieve the dual purpose of power factor correction and voltage regulation. The scheme serves itself as an efficient solution for single-stage PFC circuits applications. The work also provides a qualitative analysis to establish the expediency of the proposed ASLFR over the existing SLFR technique. A boost topology is chosen for implementation, to showcase the effectiveness of the scheme. Relevant results have been demonstrated to support the theoretical claims.

In more electric aircraft (MEA), three phase power factor correction (PFC) rectifiers of several kilowatts are required. In this paper, a three phase buck-boost derived PFC converter with inductors connected in delta configuration for aircraft application is presented. The proposed converter is operated in discontinuous conduction mode (DCM) to achieve PFC at ac input. This avoids the inner current control loop which further eliminates the current sensors. It requires only one output voltage sensor unlike five sensors in conventional PFC converter and uses a simple voltage control loop to regulate the output voltage. This makes the system cost effective, more reliable and robust. The steady state operation, design calculations and simulation results are presented. The experimental results from a 2kW laboratory prototype are also presented to confirm the operation of the proposed converter.