http://ieeexplore.ieee.org/iel5/5610941/5624686/05624745.pdf

Power electronics

High-step-up, high-efficiency, and cost-effective dc–dc converters, serving as an interfacing cell to boost the low-voltage output of renewable sources to the utility voltage level, are an important part in renewable energy systems. Over the past few years, there has been a substantial amount of studies devoted to high-step-up dc–dc converters. Among them, the category of coupled-inductor boost converters is widely researched and considered to be a promising solution for high-step-up applications. In this paper, these converters are categorized into five groups according to the major topological features. The derivation process, advantages, and disadvantages of these converters are systematically discussed, compared, and scrutinized. This paper aims to provide an introduction, review, and framework for the category of high-step-up coupled-inductor boost converters. General structures for the topologies are proposed to clarify the topological derivation process and to show potential gaps. Furthermore, challenges or directions are presented in this paper for deriving new topologies in this field.

Overview of High-Step-Up Coupled-Inductor Boost Converters

In this paper, a new control algorithm is proposed to achieve optimal dynamic performance for dc-to-dc converters under a load current change and for a given set of circuit parameters, such as the output inductor, output capacitor, switching frequency, input voltage, and output voltage. Using the concept of capacitor charge balance, the proposed algorithm predicts the optimal transient response for a dc-to-dc converter during a large signal load current change. During steady state operation, conventional current mode proportional-integral-derivative (PID) is used. During large signal transient conditions, the new control algorithm takes over. The equations needed to calculate the transient time and the required duty cycle series are presented. By using the proposed algorithm, the optimal transient performances, including the smallest output voltage overshoot/undershoot and the shortest recovery time, is achieved. In addition, since the large signal dynamic response of the power converter is successfully predicted, the large signal stability is guaranteed. Experimental results show that the proposed method produces superior dynamic performance over a conventional current mode PID controller.

A New Digital Control Algorithm to Achieve Optimal Dynamic Performance in DC-to-DC Converters

In this paper, a fixed-frequency quasi-sliding control algorithm based on switching surface zero averaged dynamics (ZAD) is reported. This algorithm is applied to the design of a buck-based inverter, and implemented in a laboratory prototype by means of a field programmable gate array (FPGA), taking into account processing speed versus computational complexity trade-off. Three control laws, namely sliding control (SC), fixed-frequency quasi-sliding ZAD and PWM-based control have been experimentally tested to highlight the features of the proposed algorithm. According to the experimental results presented in the paper, the ZAD algorithm fulfills the requirement of fixed switching frequency and exhibits similar robustness properties in the presence of perturbations to those of sliding control mode.

/pdf/a-fixed-frequency-quasi-sliding-control-algorithm-tmuexu4zx5.pdf

A fixed-frequency quasi-sliding control algorithm: application to power inverters design by means of FPGA implementation

A novel two-switch high-step-up isolated converter with voltage lift is proposed in this paper. The proposed isolated converter utilizes a transformer with low turn ratio to achieve high step-up gain. The secondary winding charges two boosting capacitors in parallel as switches during the switch-on period, and two boosting capacitors are discharged in series during the switch-off period. Thus, the converter has high voltage gain with appropriate duty ratio. In addition, by using two clamping diodes and a capacitor on the primary side, leakage energy is recycled, and the voltage spikes of the two active switches are clamped, thereby improving conversion efficiency. Finally, experimental results based on a prototype implemented in the laboratory with an input voltage of 24 V, an output voltage of 200 V, and an output power of 200 W verify the performance of the proposed isolated converter; full-load efficiency is nearly 93%.

/pdf/novel-isolated-high-step-up-dc-dc-converter-with-voltage-twuns08q5v.pdf

Novel Isolated High-Step-Up DC–DC Converter With Voltage Lift

An RCD clamp circuit is usually used in flyback converters, in order to limit the voltage spikes caused by leakage transformer inductance. Oscillation ringing appears due to the clamp diode, which deteriorates the converter's power rate. This brief describes this ringing phenomenon and the use of an RC-RCD clamp circuit for damping the clamp diode's oscillation. This clamp circuit is capable for improving a flyback converter's power ratio.

RC-RCD clamp circuit for ringing losses reduction in a flyback converter

RC-RCD clamp circuit for ringing losses reduction in a flyback converter. IEEE Trans Circuit Syst Soc

This article introduces a new method for temperature-compensated capacitance–frequency converter with a single quartz crystal oscillating in the switching oscillating circuit. The novelty of this method lies in the use of additionally connected capacitances in series with JFET switching transistors to the shunt capacitance of the quartz crystal bringing a considerable reduction of the temperature influence of AT-cut crystal frequency change in the temperature range between 0 and 50 °C. The oscillator switching method and parallel switching stray capacitances connected to the quartz crystal do not only compensate crystal's natural temperature characteristics but also any other influences on the crystal such as aging of both the crystal and other oscillating circuit elements. In addition, they also reduce the output frequency measurement error. The experimental results show that through high temperature compensation improvement of the quartz crystal characteristics, this switching method enables 20 zF resolution capacitance to frequency transduction in the range 0–4 pF to 2–45 kHz.

Temperature-compensated capacitance–frequency converter with high resolution

An already published current control strategy for the coupled-inductor buck-boost converter is able to change its aim from controlling the input current to controlling the output current, and vice versa, depending on the instantaneous operation point and the applied current references. The main drawback of the two PI-based control implementation is its slow response when the control aim is changed from one current to the other. Due to the magnetic coupling, the converter's control-to-input and control-to-output current small signal transfer functions exhibit similar first-order characteristics. Therefore, it is possible to transform the previous control scheme to a PI-based one that exhibits faster and, in certain cases, much faster transitions between input and output current control operation. The presented experiments also show that the steady-state behavior of the converter is unaffected by the new control implementation.

Fast Transitions Between Current Control Loops of the Coupled-Inductor Buck–Boost DC–DC Switching Converter

This paper investigates a control approach for achieving reliable zero-voltage switching transitions within the entire operating range of a conventional nonisolated bidirectional dc–dc converter that utilizes synchronous rectification. The approach is based on operation in the discontinuous conduction mode with a constant reversed current of sufficient amplitude, which is achieved by load-dependent variation of the switching frequency. This paper focuses on the obtained resonant voltage transitions and provides analytical models for determining the reversed current and timing parameters that would ensure safe, reliable, and highly efficient operation of the converter. In addition, the proposed approach solves the synchronous transistor's spurious turn-on and body diode reverse recovery induced issues, does not require any additional components or circuitry for its realization, and can be entirely implemented within a digital signal controller. The effectiveness and performance of the presented control approach was confirmed in a 1-kW experimental bidirectional dc–dc converter that achieved 97% efficiency over a wide range of output powers at switching frequencies above 100 kHz.

Miro Milanovič

Papers

RC-RCD clamp circuit for ringing losses reduction in a flyback converter

RC-RCD clamp circuit for ringing losses reduction in a flyback converter. IEEE Trans Circuit Syst Soc

Temperature-compensated capacitance–frequency converter with high resolution

Fast Transitions Between Current Control Loops of the Coupled-Inductor Buck–Boost DC–DC Switching Converter

DCM-Based Zero-Voltage Switching Control of a Bidirectional DC–DC Converter With Variable Switching Frequency