Ausias Garrigos

Electric Vehicle Battery Life Extension Using Ultracapacitors and an FPGA Controlled Interleaved Buck–Boost Converter

This paper describes the implementation of a hybrid energy storage system (HESS) using ultracapacitors (UCs) to protect the batteries of an electrical vehicle (EV) from high-peak currents and therefore extend their lifetime. A field-programmable gate array (FPGA) controlled interleaved bidirectional buck-boost converter working in a discontinuous conduction mode, has been designed to transfer the energy between the batteries and the UCs. The FPGA is responsible of generating all the converter gate signals and implements the control stage needed to smooth the battery current peaks. The control strategy is based on dividing the current demand of the motor into two parts (high-frequency current and low-frequency current), the batteries supply the low frequency part and the UCs supply the high-frequency part. Experimental tests have been carried out driving the EV under different scenarios. Experimental results demonstrate the good behavior of the proposed HESS, although the potential battery life extension is still under quantification. The consumption of the EV has been increased due to the converter losses, this increase is minimum under typical driving scenarios, but is quite important in start-stop driving cycles.

In-Site Real-Time Photovoltaic I–V Curves and Maximum Power Point Estimator

This paper presents a practical implementation of a photovoltaic I-V curves and maximum power point estimation algorithm (IVMPPE). The IVMPPE estimates the I-V curve and sets the operation of the solar panels at a voltage that extracts the maximum available power without tracking. The operation is based on solving the parameters of the solar array equivalent electrical model, in real time, only with the measurements of six voltage and current coordinates near the operating point. Moreover, the strategy for selecting the measured points and the discard procedures for incorrect estimated curves are also detailed. To validate the IVMPPE, it has been tested under different operating conditions, and its accuracy has been compared with the classical perturb and observe (P&O) technique. The distinguishing feature of the IVMPPE is that complete I-V model is obtained, not only the MPP, enlarging the capabilities to other fields, e.g., real-time monitoring and prediction.

Modeling the sequential switching shunt series regulator

This letter characterizes, in terms of the bandwidth and limit cycle frequency of its constituent subsystems, the sequential switching shunt series regulator -S/sup 4/R, a high-efficiency, low-mass and volume power cell devised to power the next generation of regulated power buses in telecommunication spacecrafts. Transconductance power source modeling is used to obtain linear and nonlinear models. These are used to establish a design control strategy which involves the dynamic response in large load requirements or at the end of the satellite life. Simulations and experimental results are also given to demonstrate the validity of the model.

High-Efficiency Regulation Method for a Zero-Current and Zero-Voltage Current-Fed Push–Pull Converter

A new high-efficiency regulation method for a zero-current and zero-voltage current-fed push-pull converter is presented. The method proposed is based on the use of a controlled transformer as a post-regulator, which adds or subtracts an additional voltage to the output filter of the converter. An auxiliary regulator, which only handles a percentage of the output power, controls this transformer, and therefore, results in much higher efficiency than a normal preregulator would have. The novelty of the presented converter is that regulation is achieved without affecting the zero-voltage and zero-current switching in any working conditions. Small- and large-signal models of the converter have been developed and a low-power prototype has been simulated and implemented. The good agreement, between the experimental simulations and theoretical results, validates the theoretical developments.

Influence of the Parasitic Solar Array Capacitance in the Sequential Switching Shunt Series Regulator

This work deals with the effect produced by the solar array capacitance on the sequential switching shunt regulator, S4R. In the past, silicon solar cells were widely used with practically no effect upon the solar array regulator, so that the solar array capacitance was a minor problem in the design. Nowadays, the usage of triple junction GaAs solar cells with larger parasitic capacitance has prompted new questions about power losses, steady state and dynamic responses in the S4R. In this work, the effect of the solar array capacitance is quantified by analytical models. Simulations and experimental prototyping support the models

Bidirectional High-Efficiency Nonisolated Step-Up Battery Regulator

The design and results of a high-efficiency high-power (5 kW) nonisolated bidirectional dc-dc converter is presented. High stability due to minimum phase behavior is an additional benefit of the topology. The converter is a new boost with output filter where input and output inductors are coupled. This converter is useful with any system that needs to charge and discharge backup batteries and can be applied in space, automotive, and telecom power systems.

High-Power Battery Discharge Regulator for Space Applications

This paper presents a new solution for a battery discharge regulator for high-power space applications (power-per-module ≥ 5 kW) using a high-efficiency step-up converter. Basic requirements are efficiency that is higher than 97%, mass that is lower than 2.5 kg, no galvanic isolation necessary, and a high mean time between failures. By taking into account all these parameters, the selected topology has been two interleaved boost converters with passive soft switching. Small-signal analysis of these two interleaved boost converters is also presented.

A power conditioning unit for high power GEO satellites based on the sequential switching shunt series regulator

This work describes the principles of the sequential switching shunt series regulator, S4R, an innovative solution proposed by the European Space Agency and other partners to power the next generation of high power telecommunications satellites. A comparative study between, the S4R regulated bus vs. the traditional option, the sequential switching shunt regulator regulated bus -S3R regulated bus- is performed to obtain the pros and cons of both topologies in high power (>15 kW) Geosynchronous satellites

Phase Margin Degradation of a Peak Current Controlled Converter at Reduced Duty Cycle

An inner current loop is frequently used in many switching power supplies to achieve higher stability and a good current sharing. Nevertheless, some problems derived from its practical implementation can be encountered. One problem is related to the need of filtering of the sensed current and was discovered by the authors in the implementation of a 500 W converter, when peak current control was applied by sensing the switch current. This paper will demonstrate mathematically that an RC filter not only filters out the noise but also can cause a degradation of the phase margin, especially, if the needed duty cycle is close to zero. The main reason for it is the severe distortion of the current waveform that results in an excessive phase loss. This phase loss is much larger than the expected from the filter and its delay. The problem becomes worse if we reduce the duty cycle and increase the load current. Therefore, the response to the on time slope of the current waveform is negligible, and we have only the response to a steep rising edge. We will also demonstrate that phase margin loss disappears if current is sensed at the inductor instead of the switch. In both cases, the RC filter results in a different frequency response than the one predicted with the classical peak current mode theory. These differences are analyzed in depth in this paper.

New High Power / High Voltage Battery-Free Bus for Electrical Propulsion in Satellites

In this paper a solution for the power conditioning and distribution unit (PCDU) of the solar electric propulsion module (SEPM) is proposed. The electronic propulsion system is made out of ion thrusters which need a very steady supply voltage and therefore care has to be taken during switch off of the ion thrusters (beam-out) to avoid transient overvoltages (they must be less than 2%). The new conception is a new sequential switching shunt maximum power regulator (S3MPR) consisting in a sequential switching shunt regulator (S3R), to keep the SA voltage at its maximum power point (MPP) followed by a boost regulator to produce a constant 100 V to supply the electronic propulsion (EP). The PCU has been verified by means of testing on a scaled-down Power Subsystem of 1 kW output power.