A LLC-Type Dual-Bridge Resonant Converter: Analysis, Design, Simulation, and Experimental Results

Abstract—

In this paper, a high-frequency isolated dual-bridge LLC-type resonant converter is proposed. The steady-state analysis of the proposed converter is performed using a modified fundamental harmonics approximation approach, by which the component stress can be obtained quickly without complicated calculation. Necessary and sufficient conditions for zero-voltage switching of all switches are derived too. To illustrate the usefulness of the FHA analysis for a fast design, a design example of a 100 kHz, 200 V input, 40–48 V output 300 W converter is given. Computer simulation and experiment results are included for the purpose of validation. It is shown that this converter is able to maintain zero-voltage switching operation for a wide load range while keeping high efficiency.

A Half-Bridge LLC Resonant Converter Adopting Boost PWM Control Scheme for Hold-Up State Operation

Abstract—

This paper presents a half-bridge LLC resonant converter having a boost pulse width modulation (PWM) converter characteristic for hold-up state operation. The proposed converter is based on a half-bridge LLC resonant converter structure and a single auxiliary switch is added at the primary side. The converter has two different operational characteristics. It shows the same operational characteristic with the conventional LLC resonant converters during nominal state, which is frequency modulation (FM) method. However, when ac line lost and the converter enters into the hold-up time state, which requires wide voltage gain changes, the control method of the proposed converter is changed to the PWM method using the auxiliary switch. Since the proposed converter compensates wide voltage gain variation with PWM method of the auxiliary switch rather than adopting the FM method of main switches, the frequency variation range for the LLC resonant converter is highly reduced in the proposed converter. Therefore, the transformer in the proposed converter can be designed at the optimal operating point and it results in decreased conduction loss of the magnetizing inductor current. Furthermore, the maximum voltage gain of the proposed converter is easily increased by extending the duty ratio of the auxiliary switch. It helps to decrease the link capacitance. To verify the effectiveness of the proposed circuit, operational principle will be explained and experimental results will be presented with following specification. 100 kHz of switching frequency, 250–400 V of input voltage range, 250 V of output voltage, and 75 W output power.

A Four-level Hybrid-Clamped Converter With Natural Capacitor Voltage Balancing Ability

Abstract—

This paper presents a novel four-level hybrid-clamped converter topology which is composed of eight switches and one flying capacitor per phase. The operating principle is introduced and phase-shifted pulse width modulation is used to control this converter. A detailed analysis of the average currents through the flying capacitor and neutral points of the dc-link is presented. Based on the analysis, it can be concluded that the voltages across the flying capacitor and dc-link capacitors can be naturally balanced under ideal and steady-state condition. A low-power three-phase prototype is built up and experimental results are presented to validate the proposed topology and modulation method.

A Cascaded Multilevel Inverter Based on Switched-Capacitor for High-Frequency AC Power Distribution System

Abstract—

The increase of transmission frequency reveals more merits than low- or medium-frequency distribution among different kinds of power applications. High-frequency inverter serves as source side in high-frequency ac (HFAC) power distribution system (PDS). However, it is complicated to obtain a high-frequency inverter with both simple circuit topology and straightforward modulation strategy. A novel switched-capacitor-based cascaded multilevel inverter is proposed in this paper, which is constructed by a switched-capacitor frontend and H-Bridge backend. Through the conversion of series and parallel connections, the switched-capacitor frontend increases the number of voltage levels. The output harmonics and the component counter can be significantly reduced by the increasing number of voltage levels. A symmetrical triangular waveform modulation is proposed with a simple analog implementation and low modulation frequency comparing with traditional multicarrier modulation. The circuit topology, symmetrical modulation, operation cycles, Fourier analysis, parameter determination, and topology enhancement are examined. An experimental prototype with a rated output frequency of 25 kHz is implemented to compare with simulation results. The experimental results agreed very well with the simulation that confirms the feasibility of proposed multilevel inverter.

A Bidirectional High-Frequency-Link Single-phase Inverter: Modulation, Modeling, and Control

Abstract—

This paper proposes a high-performance high-frequency-link (HFL) single-phase inverter. It offers bidirectional two-stage galvanic isolation power conversion without bulky dc link capacitors. An active clamper circuit and corresponding modulation strategy is developed to enable the proposed HFL rectifier to operate in soft-switching modes and be free of voltage spikes during device commutation. A succinct circuit model and high-performance plug-in repetitive control scheme are also developed to enable it to equally function as a high-performance conventional pulse width modulation (PWM) inverter. The experiment results on a 20-kHz HFL inverter prototype demonstrate the efficacy of the soft-switching HFL inverter and its highly promising control performance. The proposed HFL inverter offers a high-reliability, high-efficiency, high-power-density, and high-performance power conversion solution to extensive applications.

Excitation Synchronous Wind Power Generators With Maximum Power Tracking Scheme

Abstract—

This paper presents a novel excitation synchronous wind power generator (ESWPG) with a maximum power tracking scheme. The excitation synchronous generator and servo motor rotor speed tracks the grid frequency and phase using the proposed coaxial configuration and phase tracking technologies. The generator output can thus be directly connected to the grid network without an additional power converter. The proposed maximum power tracking scheme governs the exciter current to achieve stable voltage, maximum power tracking, and diminishing servo motor power consumption. The system transient and static responses over a wide range of input wind power are examined using simulated software. Experimental results from a laboratory prototype ESWPG demonstrate the feasibility of the proposed system.

Control of Reduced-Rating Dynamic Voltage Restorer With a Battery Energy Storage System

Abstract—

In this paper, different voltage injection schemes for dynamic voltage restorers (DVRs) are analyzed with particular focus on a new method used to minimize the rating of the voltage source converter (VSC) used in DVR. A new control technique is proposed to control the capacitor-supported DVR. The control of a DVR is demonstrated with a reduced-rating VSC. The reference load voltage is estimated using the unit vectors. The synchronous reference frame theory is used for the conversion of voltages from rotating vectors to the stationary frame. The compensation of the voltage sag, swell, and harmonics is demonstrated using a reduced-rating DVR.