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

Supercapacitor assisted low dropout regulators (SCALDO) with reduced switches: A new approach to high efficiency VRM designs

Supercapacitor assisted low dropout (SCALDO) regulator is a new approach to develop high efficiency DC-DC converters with supercapacitors used for energy recovery. One limitation in these topologies is that in some configurations a large number of low-speed switches are required. If the SCALDO technique is adapted to build voltage regulator modules (VRM), it is necessary to reduce number of switches combined with a high current capable LDO. A new topology-variation with less number of switches can be achieved by reconfiguring the original SCALDO and adding an extra LDO to the circuit. The paper presents a summary of some preliminary work, and experimental results for a 2.5V proof of concept-prototype

ASDTIC control and standardized interface circuits applied to buck, parallel and buck-boost dc to dc power converters

Versatile standardized pulse modulation nondissipatively regulated control signal processing circuits were applied to three most commonly used dc to dc power converter configurations: (1) the series switching buck-regulator, (2) the pulse modulated parallel inverter, and (3) the buck-boost converter. The unique control concept and the commonality of control functions for all switching regulators have resulted in improved static and dynamic performance and control circuit standardization. New power-circuit technology was also applied to enhance reliability and to achieve optimum weight and efficiency

Morphing Switched-Capacitor Converters with Variable Conversion Ratio

High-voltage-gain and wide-input-range dc-dc converters are widely used in various electronics and industrial products such as portable devices, telecommunication, automotive, and aerospace systems. The two-stage converter is a widely adopted architecture for such applications, and it is proven to have a higher efficiency as compared with that of the single-stage converter. This paper presents a modular-cell-based morphing switched-capacitor (SC) converter for application as a front-end converter of the two-stage converter. The conversion ratio of this converter is flexible and variable and can be freely extended by increasing more SC modules. The varying conversion ratio is achieved through the morphing of the converter's structure corresponding to the amplitude of the input voltage. This converter is light and compact, and is highly efficient over a very wide range of input voltage and load conditions. Experimental work on a 25-W, 6-30-V input, 3.5-8.5-V output prototype, is performed. For a single SC module, the efficiency over the entire input voltage range is higher than 98%. Applied into the two-stage converter, the overall efficiency achievable over the entire operating range is 80% including the driver's loss

Electrical performance characteristics of high power converters for space power applications

The first goal of this project was to investigate various converters that would be suitable for processing electric power derived from a nuclear reactor. The implementation is indicated of a 20 kHz system that includes a source converter, a ballast converter, and a fixed frequency converter for generating the 20 kHz output. This system can be converted to dc simply by removing the fixed frequency converter. This present study emphasized the design and testing of the source and ballast converters. A push-pull current-fed (PPCF) design was selected for the source converter, and a 2.7 kW version of this was implemented using three 900 watt modules in parallel. The characteristic equation for two converters in parallel was derived, but this analysis did not yield any experimental methods for measuring relative stability. The three source modules were first tested individually and then in parallel as a 2.7 kW system. All tests proved to be satisfactory; the system was stable; efficiency and regulation were acceptable; and the system was fault tolerant. The design of a ballast-load converter, which was operated as a shunt regulator, was investigated. The proposed power circuit is suitable for use with BJTs because proportional base drive is easily implemented. A control circuit which minimizes switching frequency ripple and automatically bypasses a faulty shunt section was developed. A nonlinear state-space-averaged model of the shunt regulator was developed and shown to produce an accurate incremental (small-signal) dynamic model, even though the usual state-space-averaging assumptions were not met. The nonlinear model was also shown to be useful for large-signal dynamic simulation using PSpice

Spacecraft power

Solar cell spacecraft power systems, and measurements of Mariner-type and Surveyor batterie

Reducing Beat Frequency Oscillation in a Two-phase Sliding Mode-controlled Voltage Regulator Module

During static and dynamic loading conditions, voltage regulator modules (VRMs) are expected to provide regulated voltage with minimal ripple even at high current requirement.  Compared to regular power supplies, VRMs repetitively experience high-frequency loading conditions that is greatly dependent on the software running in the processor utilizing them. In the scenario that when the transient load frequency is near the VRM’s switching frequency, high-magnitude and low-frequency oscillations are observed at the phase currents.  This phenomenon is called the beat frequency oscillation.  In this study, the sliding mode control principle is employed to both the voltage and current share loops of the VRM to reduce the phase currents’ beat frequency oscillations. A fixed frequency sliding mode controller is derived and extensively evaluated using the PSIM simulator.  Our results show that while maintaining equal load sharing among VRMs at less than 5% sharing error and various types of loading conditions, the sliding mode controller can reduce the beat frequency oscillation phenomenon to 20 kHz at maximum with reduced peak current values.   The output voltage is also regulated within the desired ±1.65% band