Optimization Design of Load-Independent Class-E$^{2}$ DC-DC Converter with Performance Visualization

The integration of renewable energy sources (RES), energy storage systems (ESS), and electric mobility into smart grids requires the use of dc-dc back-end power converters for adjusting voltage levels. Although a dc-dc converter applied for RES only operates in unidirectional mode, when applied to ESS or EM, the bidirectional mode is a fundamental requisite for exchanging power with the electrical power grid. In this context, this paper presents an experimental validation of a proposed bidirectional three-level dc-dc converter considering its application for smart grids. Traditionally, the dc-dc power converters of such applications are two-level converters. However, by employing a three-level topology, it is possible to improve the quality of the variables controlled by the power converter. Moreover, since the proposed dc-dc converter is controlled to produce a controlled current, the proposed current control and modulation strategies are introduced and described. A complete analysis of the operation principle of the proposed bidirectional three-level dc-dc power converter is presented, supported by experimental validation, employing a laboratory prototype.

In this paper, an integrated three-voltage-booster DC-DC (direct current to direct current) converter is proposed to achieve high voltage gain for renewable-energy generation systems. The proposed converter integrates three voltage-boosters into one power stage, which is composed of an active switch, a coupled-inductor, five diodes, and five capacitors. As compared with conventional high step-up converters, it has a lower component count. In addition, the features of leakage-energy recycling and switching loss reduction can be accomplished for conversion efficiency improvement. While the active switch is turned off, the converter can inherently clamp the voltage across power switch and suppress voltage spikes. Moreover, the reverse-recovery currents of all diodes can be alleviated by leakage inductance. A 200 W prototype operating at 100 kHz switching frequency with 36 V input and 400 V output is implemented to verify the theoretical analysis and to demonstrate the feasibility of the proposed high step-up DC-DC converter.

The high-frequency isolated power supply with low-voltage large-current output and widely fluctuating input voltage is discussed in this paper. It is described that it is difficult to achieve high efficiency of the power supply with ZVS phase-shift PWM controlled DC-DC power converter mainly due to high conduction power losses in the rectifier stage. The 2-stage DC-DC converter system configuration, which consists of boost ZVS-PWM DC-DC chopper and ZVS full-bridge high-frequency isolated DC-DC converter operating with maximum duty cycle, is presented. An ability to improve efficiency of the power conversion by using 2 stages DC-DC circuit configuration is discussed. 900W-100kHz DC-DC conversion system prototypes were built and tested. An efficiency comparison between full-bridge ZVS phase-shift PWM DC-DC power converter and 2-stage soft-switching DC-DC converter has been made. It is proved that using 2-stage DC-DC converter can improve efficiency under full load.

Electronic power converters are sources of electromagnetic interference at their input power source as well as in other neighbouring electronic equipment, and suppression of EMI is a major issue in switch-mode power converter design. By their very nature, switching converters have fast voltage and current changes that generate conducted noise due to reflected ripples in the input current. Fast switching logic loads also produce conducted noise that reflects back onto the input of the converter. In order to meet conducted emission and susceptibility standards, an LC input filter is often employed between a dc-dc converter and its power source. However, its presence, in turn, often results in degradation of dynamic performance and instability of the system even if the filter attenuation is brilliantly designed. The detrimental interaction between an input filter and a switched mode converter is a function of input filter parameters as well as supply voltage. In this paper, some design practices for EMI noise suppression are discussed for dc-dc converter applications. Then the instability problem is addressed that results from the complex interaction of dc-dc power converter with its input EMI filter. Its causes are discussed and a design procedure is suggested for its treatment by damping the input filter without over sizing or under sizing. Results corresponding to boost converter are presented to illustrate the procedure.

This paper proposes a bi-directional dc-dc z-source converter. Z-source dc-dc converter has an impedance network which performs buck-boost operations. In this the input current is continuous and also the voltage stress across the switches is less. It can also boost the input voltage using reduced passive component with better reliability and decreased cost. Compared to the existing dc-dc converter circuits, they reduce in-rush and harmonic current. Therefore this paper aims at a soft switched quasi z-source converter. That the proposed converter has the better voltage profile with most reduction of voltage regulation. H-bridge dc-dc sources are preferably connected to the voltage sources and sometimes current sources. This is used to minimize the current stress as well as to improve the system efficiency. Z-source isolated bi-directional dc-dc converter boosts the dc voltage up to the 600 V, which is used to supply to the inverter. Inverter is being incorporated with space vector modulation technique for its driver circuit control. From this that the inverted output is supplied to the asynchronous motor drive to get the dynamic responses of the drive from its performance parameters like stator phasor current, torque and speed. Respective results are analyzed by using MATLAB software.

This paper designs a DC-DC converter and rectifier with resonator for wireless power transfer module (WPTM) and solar charging with ambient light sensor (ALS) in advanced driver assistance system when vehicles moving. The proposed boost DC-DC power converter serving as DC-to-AC converter with an embedded DC rectifier to provide the first-stage DC-DC converter, and charge pump support AC-to-DC converter with an input from the DC rectifier. Two differential, cross-coupled rectifiers as the charge pump circuit mitigate the reverse-leakage issue and they are cascaded to double the output voltage. The resonator uses the coil in multi-mode to drive wireless charging functions for power receiving unit (PRU) at parking slot and traffic stop. The proposed ambient light sensor can assistance solar charging direction to control motor of solar panel. The proposed solar charging with ambient light sensor that is direction to control motor of solar panel in advanced driver assistance system (ADAS).

Using Multivariate Polynomials to Obtain DC-DC Converter Voltage Gain

An electric vehicle powered by the fuel cells called fuel cell electric vehicles has higher efficiency and lower emissions compared with the internal combustion engine vehicles. In this paper presents modeling and control of a dc-dc resonant converter interfacing fuel cell for electric vehicle. The necessary energy to move the vehicle is provided by two separate energy sources, which are fuel cell and a super capacitor. A high frequency DC-DC converter fed by fuel cell is analyzed. The mathematical model of the fuel cell is presented and the average model and the controller of the dc-dc converter is elaborated. The proposed converter is digitally simulated using the MATLAB/ Simulink/ Sim Power Systems software. The dynamic performances of the electric vehicle drives are examined for the standardized European speed cycle type.

This paper presents some experimental results and practical evaluations of a high-frequency linked three-level phase-shift ZVS-PWM half bridge DC-DC high power converter for distributed DC power feeder. This new DC-DC converter with neutral point clamping and flying capacitor hybrid configuration is implemented by modifying the high-frequency-linked HB soft switching PWM DC-DC power converter with high side and low side two active edge resonant cells, which is previously-developed by the authors. The operating principle of the three-level phase-shift ZVS-PWM DC-DC converter and its experimental and simulation results including power regulation characteristics vs. phase-shifted angle and power conversion efficiency characteristics in addition to power loss analysis are illustrated and discussed from a practical point of view, along with the remarkable advantageous features as compared with previously-developed soft switching PWM DC-DC converter with high frequency AC link.

In this paper, a review of the common techniques used for high step-down dc-dc voltage conversion is presented. First, the limitations of conventional buck & synchronous rectifier buck converters used for high step down dc-dc voltage conversion which include narrow duty cycle, high voltage stress, large ripple and low efficiency are briefly discussed. Then various topologies of non-isolated step-down dc-dc converters are reviewed and discussed. The topologies/techniques used for high step down dc-dc conversion are divided into various groups which include interleaved, quadratic, tapped, switched capacitor, switched inductor, coupled inductor, multi level and buck converter with three state switching cells. Each group of converters is briefly discussed, main circuit structure of each topology is given and their features and limitations are given. Finally a comparison of all the discussed topologies is carried out based on some common features.

In recent years, due to the energy crisis and serious environmental problems, the use and development of new energy has become the focus of research. Therefore, the application of new energy technologies has increased the demand for direct current to direct current (DC-DC) converters. The improvement of converter capability effectively enhances the functions of DC-DC converters, which makes it easy for secondary converters to meet the requirements of voltage gain, and expands the input voltage range of DC-DC converters, thereby having a good prospect in new energy applications. However, due to the many drawbacks of the quadratic Boost converter, such as pressure rise limitation, high switching stress, in order to reduce the working pressure of the improved quadratic Boost high gain converter and improve its operating performance, it is necessary to optimize it. Based on the application scenario of an modified converter for quadratic Boost high gain DC-DC, and taking the constant off time control method as an example, this paper conducted research to accurately recognize the current status of the converter and improve the utilization efficiency of the converter. In this paper, four groups of traditional converters and two types of improved quadratic Boost high gain DC-DC converters were selected as experimental objects for comparative analysis of images and data. The results showed that the conversion efficiency of the constant off time control method in the modified DC-DC converter based on quadratic high gain was 7.03 % higher than that of the traditional converter, while also improving the conversion efficiency of voltage gain and reducing switching stress, with higher safety. This indicated that the improved DC-DC converter with secondary high gain has better effects and wider application scenarios, thereby better serving new energy systems.

DC-DC converters with series-resonant inverter (SRI) may arouse interest among scientists and converter equipment designers due to their applicability at solar power plants (SPP) in particular. Zero-current switching (ZCS) and/or zero-voltage switching (ZVS) of semiconductor devices could be easily implemented in such DC-DC converters. This could allow reducing power losses when switching devices considerably as well as operating DC-DC converters at higher frequencies with high efficiency. A basic diagram for the power section of the bridge DC-DC converter as well as the operating principle of this section in DC-DC converters with SRI for SPP is discussed in the Theory Section of the paper. There are a great number of analog control units on serial chips to control resonant DC-DC converters, but they are intended for symmetric control only. The paper provides a scheme for implementing the algorithm for asymmetric control of the resonant DC-DC converter power transistors on discrete components in the form of a virtual model in the Matlab/Simulink environment. So far, the asymmetric control method is described only in one foreign paper providing current oscilloscope patterns of the resonant circuit and control voltages across MOSFET transistor gates of the DC-DC converter as well as the control system flowchart. The experimental part of the article presents the simulation results (transient, steady state, external characteristics, dependences for the efficiency of the converter). The obtained characteristics are consistent with the results of theoretical calculations presented in previous papers of the authors.

<span>A dc-dc zeta converter is a switch mode dc-dc converter that can either step-up or step-down dc input voltage. In order to regulate the dc output voltage, a control subsystem needs to be deployed for the dc-dc zeta converter. This paper presents the dc-dc zeta converter control. Unlike conventional dc-dc zeta converter control which produces a controller based on the nominal value model, we propose a convex polytope model of the dc-dc zeta converter which takes into account parameter uncertainty. A linear matrix inequality (LMI) is formulated based on the linear quadratic regulator (LQR) problem to find the state-feedback controller for the convex polytope model. Simulation results are presented to compare the control performance between the conventional LQR and the proposed LMI based controller on the dc-dc zeta converter. Furthermore, the reduction technique of the convex polytope is proposed and its effect is investigated.</span>

This chapter describes DC-DC converters which are expected to become important components in large DC transmission grids. Similarly as with AC transformers in AC transmission systems, DC-DC converters enable interconnection between two DC systems with different voltage levels. However, some DC-DC converter topologies will provide a range of other functions including breaking DC circuits, power flow control and galvanic isolation. While the description of the DC-DC systems includes many design details, the application of DC-DC converters is still a concept, and the detailed design of these systems needs further in depth studies. The information provided in the chapter focuses on the functional requirements of the DC-DC systems, which are described in significant detail in this chapter. There are two families of DC-DC converters: Non-isolated DC-DC and Isolated DC-DC. Non-Isolated DC-DC is the lowest-cost topology, with the costs and losses expected to be 1.1–1.3 pu relative to a similarly rated single MMC VSC converter. The design, modeling and control of Non-Isolated DC-DC systems are decribed. The responses during DC faults are also analysed in some depth and DC fault simulation results are presented using a typical 600 MW DC-DC test system. The isolated DC-DC will have an internal AC transformer which provides galvanic isolation between two DC systems, while costs and losses are expected to be around 2 pu compared with a similarly rated MMC VSC converter. The design, modeling and control of this DC-DC topology is described based on the application of CIGRE’s DC grid test system. DC fault responses are also analysed and illustrated using simulation responses with a typical 600 MW test system. The DC-DC converter applications for interconnecting high voltage with medium voltage DC systems are also described. This application requires higher voltage step ratio and some specific DC-DC converter topologies are found to be more suitable than others. Typical applications would include interconnection to existing medium voltage DC systems like those with renewable energy plants.

This study introduces design, integration, control, and analysis of a hybrid microgrid (MG) testbed including a 300 kW wind energy plant of three 100-kW permanent magnet synchronous generators (PMSGs), 50 kW solar energy plant of 200 solar panels, and a 50 kW fuel cell stack. Generation side of the hybrid plant coupled on 120V dc bus where wind energy plant consists of uncontrolled diode rectifier and dc-dc buck converter rail while the solar and fuel cell plants are just controlled by dc-dc buck converters. The energy conversion of solar energy plant is operated by using proportional-integral (PI) controller assisted perturb and observe (P&O) maximum power point tracking (MPPT) algorithm. The dc-dc converters of the left generators are operated with PI controllers. All the dc-dc converters are constituted with mosfets that are switched at 30 kHz. The islanded AC grid of the plant is built by three-phase inverter that generates 480 V 60 Hz industrial voltages of the U.S. The inverter is operated by a sinusoidal pulse width (SPWM) modulator where the modulation index is set to 0.8 and switching frequency to 5 kHz. The proposed testbed is assumed essential to test and validate several case studies in terms of MG and renewable energy source integration issues. The most recent power control methods (PQ) and amplitude controls (V-f) can also be implemented by using the presented testbed.