Local control of multiple module converters with ratings-based load sharing

Multiple module dc-dc converters show promise in meeting the increasing demands on ef- ficiency and performance of energy conversion systems. In order to increase reliability, maintainability, and expandability, a modular approach in converter design is often desired. This thesis proposes local control of multiple module converters as an alternative to using a central controller or master controller. A power ratings-based load sharing scheme that allows for uniform and non-uniform sharing is introduced. Focus is given to an input series, output parallel (ISOP) configuration and modules with a push-pull topology. Sensorless current mode (SCM) control is digitally implemented on separate controllers for each of the modules. The benefits of interleaving the switching signals of the distributed modules is presented. Simulation and experimental results demonstrate stable, ratings-based sharing in an ISOP converter with a high conversion ratio for both uniform and non-uniform load sharing cases

The Essential Role and the Continuous Evolution of Modulation Techniques for Voltage-Source Inverters in the Past, Present, and Future Power Electronics

The cost reduction of power-electronic devices, the increase in their reliability, efficiency, and power capability, and lower development times, together with more demanding application requirements, has driven the development of several new inverter topologies recently introduced in the industry, particularly medium-voltage converters. New more complex inverter topologies and new application fields come along with additional control challenges, such as voltage imbalances, power-quality issues, higher efficiency needs, and fault-tolerant operation, which necessarily requires the parallel development of modulation schemes. Therefore, recently, there have been significant advances in the field of modulation of dc/ac converters, which conceptually has been dominated during the last several decades almost exclusively by classic pulse-width modulation (PWM) methods. This paper aims to concentrate and discuss the latest developments on this exciting technology, to provide insight on where the state-of-the-art stands today, and analyze the trends and challenges driving its future

Effect of the output impedance in multiphase active clamp buck converters

Passive current sharing in multiphase converters, where resistive losses are not dominant, is a quite complex goal. In this paper, an averaged model of an active clamp buck converter was obtained. It has been checked that this topology presents high output impedance. This property is used like a lossless passive equalization. The principle of operation, theoretical analysis, simulation, and experimental results are presented, taken from a three-stage laboratory prototype.This work was supported by the Ministry of Education and Science, Spain, under Research Project COMPAS (Code DPI2007-64135)

Phase substitution of spare converter for a failed one of parallel phase staggered converters

Failure detection and substitution of a spare module is provided in a system having a plurality of phase staggered modules connected in parallel to deliver regulated voltage from an unregulated source. Phase control signals applied to the active converter modules are applied to the spare module through NOR gates associated with and disabled by the power output of respective modules such that failure of any one enables its phase control signal to be applied to the spare module, thus controlling the spare module to operate in the phase position of the failed module. A NAND gate detects when any one active module fails and enables a gate in the spare module, thus activating the spare module

New Control Strategy for Energy Conversion Based on Coupled Magnetic Structures

In this paper, a new strategy for energy conversion based on a coupled magnetic structure is presented. A proper control of the input voltages provides constant output voltage at any time and ideally no output filter is required and no energy is stored, enabling very fast dynamics and low losses in the converter since switching frequency can be very small. Ideal features and actual limitations of the proposed concept are analyzed. A prototype with a two-input magnetic structure is built in order to prove the concept

Single-carrier phase-disposition PWM techniques for multiple interleaved voltage-source converter legs

Interleaved converter legs are typically modulated with individual carriers per leg and phase-shifted PWM (PS-PWM) as it facilitates current balancing amongst the legs. Phase-disposition PWM (PD-PWM), despite the better harmonic performance, cannot be directly used due to the resulting current imbalance that may damage the converter. This paper addresses the current sharing issue and proposes a single-carrier PD-PWM technique for multiple leg two-level converters based on a hierarchy scheme derived from current sorting algorithms. An extension of the proposed algorithm through a switching state feedback loop, limiting the average switching frequency, is also developed. In both cases, the load current is shared amongst the legs and the high-quality of the output voltages and currents is maintained while the circulating currents amongst the converter legs are kept to a minimum. Simulation results demonstrate the method for multiple interleaved legs as well as its current sharing capabilities for high-power applications. Experimental results from a low-power laboratory prototype validate the operation of the proposed approach.Peer ReviewedPostprint (published version

Design and development of multiphase buck converters for voltage regulator modules

Modern microprocessors in high-power applications require a low input voltage and a high input current, necessitating the use of multiphase buck converters. As per microprocessor computing complexity, the power requirements of the switching converter will also be more important and will be increasing as per load demand. Previous studies introduced some methods to achieve the advantages associated with multiphase regulators. This paper presents an effective closed closed-loop control scheme for multiphase buck converters that reduces ripple and improves transient response. It is suitable for applications that require regulated output voltage with effectively reduced ripple. The analysis began with a simulation of the entire design using the OrCAD tool, followed by the construction of a hardware setup. Experiments on a 200 Khz, 9 V, 12 A, 2-phase buck voltage regulator were conducted and the proposed experiment found to be useful

Core-less Multiphase Converter with Transformer Coupling

A coupled multiphase converter where the coupling among the phases is done using core-less planar transformers is presented in this paper. Operating principle of the transformer-coupled converter has been presented previously in the literature and in this paper this concept is applied to develop a core-less converter. Two prototypes operating at high frequency (4 MHz), with low profile (3 mm - 4 mm) and 60 W of output power, with two different core-less transformers are presented. Main advantages of applying this concept at high frequency are size reduction and operation with core-less transformers. This topology can be considered as a dc-dc transformer and applications for this topology can be `dc-dc transformers' for two-stage power supply systems and voltage scaling power supplies

Single-Phase On-Board Integrated Battery Chargers for EVs Based on Multiphase Machines

The paper considers integration of multiphase (more than three phases) machines and converters into a single-phase charging process of electric vehicles (EVs) and, thus, complements recently introduced fast charging solutions for the studied phase numbers. One entirely novel topology, employing a five-phase machine, is introduced and assessed jointly with three other topologies that use an asymmetrical nine-phase machine, an asymmetrical six-phase machine, and a symmetrical six-phase machine. In all topologies, both charging and vehicle-to-grid (V2G) mode are viable. Moreover, all are capable of unity power factor operation. A torque is not produced in machines during charging/V2G process so that mechanical locking is not required. Hardware reconfiguration between propulsion and charging/V2G mode is either not required or minimized by using a single switch. Theoretical analysis of operating principles is given, and a control scheme, applicable to all topologies and which includes current balancing and interleaving strategy, is developed. Finally, operation of all topologies is compared by means of experiments in both charging and V2G mode, with a discussion of influence of current balancing and interleaving strategy on the overall performance