Stefanos N. Manias

An active power factor correction technique for three-phase diode rectifiers

A novel active power factor correction method for power supplies with three-phase front-end diode rectifiers is proposed and analyzed. The implementation of this method requires the use of an additional single switch boost chopper. The combined front-end converter draws sinusoidal AC currents from the AC source with nearly unity input power factor while operating at a fixed switching frequency. It is shown that when the active input power factor correction stage is also used to regulate the converter DC bus voltage, the converter performance can improve substantially in comparison with the conventional three-phase AC-to-DC converters. These improvements include component count reduction, simplified input synchronization logic requirements, and smaller filter refractive components. Theoretical results are verified experimentally. The proposed method has the disadvantage of substantially increasing the current stresses of the switching devices and the high-frequency ripple content of the prefiltered AC input currents. >

Designing a new generalized battery management system

Battery management systems (BMSs) are used in many battery-operated industrial and commercial systems to make the battery operation more efficient and the estimation of battery state nondestructive. The existing BMS techniques are examined in this paper and a new design methodology for a generalized reliable BMS is proposed. The main advantage of the proposed BMS compared to the existing systems is that it provides a fault-tolerant capability and battery protection. The proposed BMS consists of a number of smart battery modules (SBMs) each of which provides battery equalization, monitoring, and battery protection to a string of battery cells. An evaluation SBM was developed and tested in the laboratory and experimental results verify the theoretical expectations.

Comparison of state of the art multilevel inverters

In this paper, a comparison between existing state of the art multilevel inverter topologies is performed. The topologies examined are the neutral point clamp multilevel inverter (NPCMLI) or diode-clamped multilevel inverter (DCMLI), the flying capacitor multilevel inverter (FCMLI) and the cascaded cell multilevel inverter (CCMLI). The comparison of these inverters is based on the criteria of output voltage quality (Peak value of the fundamental and dominant harmonic components and THD), power circuitry complexity, and implementation cost. The comparison results are based on theoretical results verified by detailed simulation results.

Direct Model Predictive Control: A Review of Strategies That Achieve Long Prediction Intervals for Power Electronics

Direct model predictive control (MPC) strategies that achieve long prediction horizons with a modest computational complexity are reviewed in this article, focusing on power electronics applications. In many MPC problems, a long prediction horizon is required to ensure an adequate closed-loop performance in steady state and to avoid stability issues. However, the computational effort of solving the optimization problem underlying MPC problems with long prediction horizons is often very great, making the implementation of such schemes in real time a difficult and challenging task. To overcome this difficulty, three established methodologies are surveyed that yield long prediction horizons with a modest computational burden. Case studies are investigated to substantiate the merits of these schemes. More specifically, for dc?dc boost converters, a move blocking strategy is reviewed, and for ac medium-voltage (MV) drives, both an extrapolation and an event-based horizon strategy are examined.

An AC-to-DC Converter with Improved Input Power Factor and High Power Density

A novel single-phase switch-mode rectifier (SMR) structure is proposed and analyzed. The proposed converter structure employs a synchronous front-end rectifier (SFER) stage which provides high-quality input characteristics with small input filtering. Consequently the proposed converter structure exhibits high power density and has low implementation cost.

Analysis and design of a three-phase offline DC-DC converter with high-frequency isolation

Single-phase offline switch-mode rectifiers (or, offline DC-DC converters) face severe component stresses in applications above 10 kW. This study shows that in three-phase switch-mode rectifier (SMR) topologies, component stresses are reduced and performances improved substantially. These improvements include faster response times, reduced switching stresses of the power semiconductor devices, and reduced size and rating of associated reactive components. The authors also present an analysis and design approach for three-phase SMR converters under large input-voltage and load variations. Output voltage control is achieved by varying the duty cycle of the inverter power semiconductor switches. The theoretical results are verified experimentally.<<ETX>>

Direct Voltage Control of DC–DC Boost Converters Using Enumeration-Based Model Predictive Control

This paper presents a model predictive control (MPC) approach for dc-dc boost converters. A discrete-time switched nonlinear (hybrid) model of the converter is derived, which captures both the continuous and the discontinuous conduction mode. The controller synthesis is achieved by formulating an objective function that is to be minimized subject to the model dynamics. The proposed MPC strategy, utilized as a voltage-mode controller, achieves regulation of the output voltage to its reference, without requiring a subsequent current control loop. Furthermore, a state estimation scheme is implemented that addresses load uncertainties and model mismatches. Simulation and experimental results are provided to demonstrate the merits of the proposed control methodology, which include a fast transient response and a high degree of robustness.

Fast Photovoltaic-System Voltage- or Current-Oriented MPPT Employing a Predictive Digital Current-Controlled Converter

In this paper, a photovoltaic (PV)-system maximum power point (MPP) tracking (MPPT) control strategy employing a predictive digital current-controlled converter implemented in conventional hardware resources is presented. Two current programmed controllers (finite-state predictive control and valley current control) have been integrated into a system with current- or voltage-oriented MPPT. The modifications applied to the perturb-and-observe algorithm enable the MPP tracker to interact rapidly with the controller accounting also for abrupt irradiance drops by considering voltage and current limitations. The implementation of digital control in PV systems entails significant advantages of speed and accuracy, although the controller converges correctly at the MPP under irradiance variations featuring fast dynamic response. The proposed controller scheme has been experimentally demonstrated on a digitally current-controlled boost converter delivering power from a PV system.

A Novel Sinewave in AC to DC Converter with High-Frequency Transformer Isolation

A novel Switch-Mode-Rectifier (SMR) structure is proposed and analyzed in this paper. The proposed converter structure employs a high-frequency sine PWM cycloconverter to provide high-frequency ohmic isolation between the source and the load. Furthermore, it draws high-quality current from the ac source thus requiring only small input reactive components. Consequently, the proposed converter structure exhibits high power density and has low implementation cost.

A Novel Four-Level Voltage Source Inverter—Influence of Switching Strategies on the Distribution of Power Losses

In this paper, a novel four-level inverter will be presented and analyzed. The proposed inverter topology, which is composed of a conventional two-level and a three-level neutral-point clamped (NPC) inverter, is suitable for high-voltage and high-power applications. The proposed inverter, when it is compared with the conventional four-level NPC pulsewidth modulation inverter, exhibits the following advantages: a) ability of changing the power losses distribution profile among the devices by selecting a suitable switching strategy; b) reduction of total inverter power semiconductor device losses; c) ability of bidirectional operation for all power semiconductor switches; and d) easy implementation using existing power semiconductor modules. The effect of conduction and switching losses profiles of the proposed inverter for different switching strategies is examined under different loads, power factors, and modulation indices. The dc-link capacitors voltages are effectively balanced via a proposed self-voltage balancing topology, without the need of isolated dc voltage sources or additional voltage stabilizing circuits. Finally, the theoretical results are confirmed by simulation and experimental results