Power electronics contribution to renewable energy conversion addressing emission reduction: Applications, issues, and recommendations

A new asymmetric half-bridge (HB) resonant converter for dc/dc power system with a wide range of low input voltage is proposed in this paper. The proposed converter is easily derived based on the switch integration technique, merging a buck–boost, which is the same with the active-clamp forward's primary circuit, and the HB LLC resonant converter. By adopting the buck–boost circuit in front of the HB LLC resonant converter, higher input voltage of LLC resonant converter stage can be achieved. As a result, the primary conduction loss can be significantly reduced. In addition, to cover wide input voltage range, an asymmetric pulse width modulation control is applied. It can mitigate the design limitation for a high efficiency. Moreover, the proposed converter can achieve not only the small conduction loss and the optimal design for high efficiency, but also high power density and low cost due to the switch integration technique. The validity of the proposed converter is confirmed by the experimental results of a prototype converter with 36–72 V DC input and 300 W (12 V/25 A) output.

An Asymmetric Half-Bridge Resonant Converter Having a Reduced Conduction Loss for DC/DC Power Applications With a Wide Range of Low Input Voltage

This paper addresses the concept of a wirelessly powered and battery-free wireless sensor for the cyber–physical systems dedicated to the structural health monitoring applications in harsh environments. The proposed material architecture is based on a smart mesh wireless sensor network composed of sensing nodes and communicating nodes. The sensing nodes are used to sense the physical world. They are battery-free and wirelessly powered by a dedicated radiofrequency source via a far-field wireless power transmission system. The data collected by the sensing nodes are sent to the communicating nodes that, between others, interface the physical world with the digital world through the Internet. A prototype of the sensing node—using a LoRaWAN uplink wireless communication and temperature and relative humidity sensor—has been manufactured, and the experiments have been performed to characterize it. The experimental results prove that the periodicity of measurement and communication can be controlled wirelessly by using only the wireless power transmission downlink. In this paper, we highlight the performance of this complete implementation of a wirelessly powered and battery-free wireless sensing node—not yet integrated or miniaturized—designed for implementing complete cyber–physical systems and based on the simultaneous wireless information and power transfer. Finally, an investigation of comparable implementations of the battery-free sensing nodes for the cyber–physical systems is carried out.

/pdf/implementation-of-a-battery-free-wireless-sensor-for-cyber-2hin6pgh4t.pdf

Implementation of a Battery-Free Wireless Sensor for Cyber-Physical Systems Dedicated to Structural Health Monitoring Applications

LLC resonant converter is a prevalent isolated dc/dc topology due to its high efficiency, high power density, and simple structure. However, it is challenging to optimize the design of conventional LLC converter in wide gain range applications. Therefore, modifications either on the circuit structure or control strategy are necessary to improve its voltage regulation performance. This paper presents a comprehensive overview of recent evolvements of LLC topology in wide voltage gain applications. The broad applications of wide gain LLC converters, which include hold-up operation, wide input voltage range, and wide output voltage range, are investigated. State-of-the-art wide gain LLC solutions are reviewed and classified into four categories. Benefits and constraints of different solutions are addressed in detail. Finally, the circuit selection principles for different application backgrounds are summarized with a comparative study of different configurations.

Wide Voltage Gain Range LLC DC/DC Topologies: State-of-the-Art

This paper addresses the practical implementation of a wireless sensors network designed to actualize cyber-physical systems that are dedicated to structural health monitoring applications in the construction domain. This network consists of a mesh grid composed of LoRaWAN battery-free wireless sensing nodes that collect physical data and communicating nodes that interface the sensing nodes with the digital world through the Internet. Two prototypes of sensing nodes were manufactured and are powered wirelessly by using a far-field wireless power transmission technique and only one dedicated RF energy source operating in the ISM 868 MHz frequency band. These sensing nodes can simultaneously perform temperature and relative humidity measurements and can transmit the measured data wirelessly over long-range distances by using the LoRa technology and the LoRaWAN protocol. Experimental results for a simplified network confirm that the periodicity of the measurements and data transmission of the sensing nodes can be controlled by the dedicated RF source (embedded in or just controlled by the associated communicating node), by tuning the radiated power density of the RF waves, and without any modification of the software or the hardware implemented in the sensing nodes.

https://www.mdpi.com/1424-8220/19/7/1510/pdf

LoRaWAN Battery-Free Wireless Sensors Network Designed for Structural Health Monitoring in the Construction Domain

This letter presents a new single-phase 13-level switched-capacitor inverter with a reduced number of switches and a voltage boost gain of 6. The proposed topology with a single dc source can achieve 13-level output, sextuple boost, and self-voltage balance of capacitors using only 14 switches. The proposed inverter does not use a back-end H-bridge with four switches that must withstand the peak load voltage, and the voltage stress of all switches does not exceed half of the peak load voltage. The operation principle including the self-voltage balance of capacitors is described in detail. An analysis of the proposed inverter in comparison to recent topologies with a single-input dc source is performed mainly in terms of the number of switches and cost function. Simulation and experimental results verify the feasibility of the proposed topology.

A High Step-Up Switched-Capacitor 13-Level Inverter With Reduced Number of Switches

In photovoltaic applications, many previous research works have focused on pulsewidth modulation (PWM) resonant converters in order to achieve a high efficiency with a wide input voltage range. Conventional approaches utilized symmetric boosting modulation at the secondary side rectifier to obtain a symmetric operation, and they utilized two boosting modes in a switching period. Among various rectifier structures, the voltage doubler structure has a strong advantage due to a small number of components. However, it suffers from serious hard switching losses in the secondary side rectifier. In this paper, a new converter with a novel asymmetrical modulation is proposed and verified. The strong point of the proposed converter is that it eliminates hard switching turn- on losses from the rectifier, while maintaining the minimized number of components. Although the proposed converter adopts an asymmetric modulation, the offset current on the transformer becomes zero inherently. Furthermore, a “forced half resonance” operation of the proposed converter keeps rms current stresses at the same level as conventional converter although it has a higher peak current. Accordingly, the proposed converter achieves a superior efficiency with the minimum number of components at 35–25 V input and 380 V/300 W output specification.

PWM Resonant Converter With Asymmetric Modulation for ZVS Active Voltage Doubler Rectifier and Forced Half Resonance in PV Application

A conventional phase-shifted full-bridge (PSFB) converter is one of the most promising topologies in high-efficiency and high-power applications because of its small RMS current, inherent zero-voltage switching capability, and clamped voltage stress of the primary switches. However, when the PSFB converter operates with a small duty ratio, a large freewheeling current of an output inductor flows in the primary side, and it causes a large circulating current. In addition, it has a large voltage stress in the rectifier diodes due to a voltage ringing between parasitic components. To solve these problems, a new PSFB converter with a coupled inductor rectifier (CIR) is proposed in this paper. By adopting the CIR structure in the PSFB converter instead of the full-bridge rectifier, the proposed converter eliminates the freewheeling current in the primary side, which significantly reduces the primary circulating current. In addition, the two rectifier diodes of the CIR do not have voltage ringing. As a result, the proposed converter not only reduces the conduction loss in the primary side, but can also use two diodes in the rectifier with a low voltage rating. The effectiveness and feasibility were verified with a 320–400 V input and 56-V/12.8-A output prototype.

High-Efficiency Phase-Shifted Full-Bridge Converter With a New Coupled Inductor Rectifier (CIR)

A conventional asymmetrical half-bridge (AHB) converter is one of the most promising topologies in low-to-medium power applications because of zero-voltage switching of all switches and small number of components. However, when the converter is designed taking a hold-up time into consideration, it has a large DC offset current in a transformer and a small transformer turns-ratio. To solve these problems, a new AHB converter with an integrated boost converter is proposed in this letter. Because the proposed converter compensates for the hold-up time using the integrated boost converter without additional loss in the nominal state, it can achieve the optimized efficiency regardless of the hold-up time. The effectiveness and feasibility are verified with a 250–400-V input and 45 V/3.3 A output prototype.

A High-Efficiency Asymmetrical Half-Bridge Converter With Integrated Boost Converter in Secondary Rectifier

A conventional asymmetrical half-bridge (AHB) converter is one of the most promising topologies in low-power applications because of the zero-voltage switching (ZVS) of all switches and the small number of components. However, when it operates with an asymmetrical duty ratio, it has a large dc-offset current in the transformer, which increases the size and core loss of the transformer. Moreover, because the dc-offset current decreases ZVS energy for one of the half-bridge switches, it has low efficiency in a light load condition. In addition, because most of the output current is concentrated in high-voltage-rating diodes that have large forward voltage drops, large conduction loss occurs in the secondary rectifier. To solve these problems, a new AHB converter with a coupled inductor rectifier (CIR) is proposed in this paper. By adopting the CIR structure in the AHB converter, the proposed converter not only eliminates the dc-offset current in the transformer, but it also has equalized current stress in the rectifier diodes. As a result, the proposed converter achieves high efficiency in entire load condition, compared to an AHB converter with a full-bridge rectifier. The effectiveness and feasibility are verified with a 250–400 V input and 100 V/200 W output prototype.

Jung-Kyu Han

Papers

A High Step-Up Switched-Capacitor 13-Level Inverter With Reduced Number of Switches

PWM Resonant Converter With Asymmetric Modulation for ZVS Active Voltage Doubler Rectifier and Forced Half Resonance in PV Application

High-Efficiency Phase-Shifted Full-Bridge Converter With a New Coupled Inductor Rectifier (CIR)

A High-Efficiency Asymmetrical Half-Bridge Converter With Integrated Boost Converter in Secondary Rectifier

High-Efficiency Asymmetrical Half-Bridge Converter With a New Coupled Inductor Rectifier (CIR)