Converter For Renewable Energy Applications Research Articles

Novel Full-Bridge PWM Resonant Converter: Analysis and Implementation

ABSTRACTA soft-switching full-bridge converter for renewable energy conversion applications is presented. Phase-shifted full-bridge DC/DC converter with a resonant tank is used to realize zero-voltage switching turn-on for switches and zero-current switching for rectifier diodes within nearly entire load range. Therefore, the switching losses of switches and rectifier diodes are improved. To overcome the drawback of a wide range of switching frequency in the conventional resonant converters, fixed frequency pulse-width modulation is adopted to generate the switching signals and also to regulate the output voltage. The transformer primary and secondary windings are connected in parallel and series, respectively, to reduce the current ratings of transformer primary windings and also balance the primary currents for low input voltage applications. Full-bridge diode rectifier is used to reduce the voltage ratings of rectifier diodes for high output voltage applications. Experiments are provided to verify the theoretical analysis and performance of the proposed circuit.

Tuning of Synchronous-Frame PI Current Controllers in Grid-Connected Converters Operating at a Low Sampling Rate by MIMO Root Locus

Current controller performance is key in grid-connected power converters for renewable energy applications. In this context, a challenging scenario is arising in multi-megawatt wind turbines, where sampling and switching frequencies tend to be lower and lower as power ratings increase. This strongly affects achievable control time constant. With this perspective, this paper presents a systematic procedure for accurate dynamics assessment and tuning of synchronous-frame proportional–integral current controllers, which is based on linear control for multiple-input–multiple-output (MIMO) systems. The dominant eigenvalues of the system are calculated with explicit consideration of time-delay and cross-coupling terms, two factors which clearly impair the system dynamics when considering a low sampling frequency. The proposed methodology is summarized as follows. First, the plant and controller matrices are modeled in state space. Subsequently, the characteristic polynomial of the closed-loop system is obtained and a computer-aided parametric analysis is performed to calculate the MIMO root locus as a function of the control gain. By its inspection, it is possible to identify the gain, which minimizes the current closed-loop time constant. This tuning is suitable for wind turbine applications, taking into consideration cascaded-control structures and grid-code requirements. The validity and accuracy of the analysis is fully supported by experimental verification.

A step‐up PWM DC–DC converter for renewable energy applications

SummaryA step‐up pulse width modulation (PWM) direct current (DC)–DC converter is presented in this paper, which has its origin in quasi Z‐source inverter. Analysis of this converter in steady state is presented, and relevant expressions are derived for the proposed converter operating in continuous conduction mode. The power loss expressions for each component of the converter are derived, and thereby, obtained expressions for overall converter efficiency are presented. Further, a dynamic model is derived to design an appropriate controller for this converter. The simulation and experimental results are presented to support the theoretical analysis. The advantages such as continuous input current, high step‐up gain at lower duty ratio, and common ground for source, load, and switch makes the converter suitable for renewable energy applications. Copyright © 2015 John Wiley & Sons, Ltd.

Comparison of 8-kW CCTT IM and Discrete Inductor Interleaved Boost Converter for Renewable Energy Applications

This paper presents a comparison of two magnetic component topologies for use in a high-power high-current dc-dc boost preregulator for renewable applications. The industry-standard two-phase (2L) interleaved dc-dc boost converter consisting of two discrete toroid magnetic components is considered as the baseline design. A 3C92 CCTT-core split-winding integrated magnetic (CCTT IM) is developed and compared for similar conditions. The topologies are compared for the same worst case phase-current ripple conditions. First, the baseline industry-standard 2L design is presented, which consists of a toroidal magnetic component along with stranded copper conductors, which are used to reduce the effects of ac copper loss. The CCTT IM component is designed for the same worst case phase-current ripple as this allows for a size saving with respect to the baseline design. The CCTT IM boxed volume is investigated as the number of turns is varied, but for a like-for-like comparison, the final CCTT IM design has the same number of turns and copper cross-sectional area as the 2L baseline design. A 2D finite element analysis (FEA) is used in order to validate and optimize the designs. The 8-kW experimental results are presented that indicate that the CCTT IM option allows for an approximate reduction of 50% in both magnetic mass and boxed volume with respect to the 2L toroid inductors. Critically, this size saving does not come at the expense of reduced efficiency, and the CCTT IM exhibits greater efficiency than the 2L baseline design. The IM does require additional input capacitance compared to the 2L design. The overall $LC$ filter of the IM design, comprising the boost magnetics and input capacitance, is reduced by approximately 20% in volume and 44% in mass compared to the 2L design.

Modeling and Simulation of Multi-input Bi-directional Boost Converter for Renewable Energy Applications using MatLab/Simulink

Modeling and Simulation of Multi-input Bi-directional Boost Converter for Renewable Energy Applications using MatLab/Simulink

Multi-Input Boost Converter for Hybrid PV and Wind Generator Systems

A renewable energy source that works alone can’t achieve customers’ requirements for a stable power supply. Therefore, the paper proposes a multi-input converter for hybrid renewable energy system. This converter is designed for two input sources, PV and wind generator in order to design high efficiency and high performance converters for renewable energy applications. The proposed multi-input converter is composed by interleaved technique with two step-up converters and the two inputs are accommodated with some extra semiconductors, inductances and diodes. The modes of operation based on the status of the four switches, where S1 and S2 operate as main switches in order to deliver energy from both voltage sources. A constant output power to the load is provided by switching S3 switch, which guarantied the appropriate output voltage by reduce the ripple and improve the reliability. Simulations of multi-input converter has been performed using MATLAB/SIMULINK. The simulation results confirm the validity of the proposed method, which can be seen as a promising new topology that ensure multi-input converter suitable for renewable energy applications.

An Integrated Four-Port DC/DC Converter for Renewable Energy Applications

This paper proposes a novel converter topology that interfaces four power ports: two sources, one bidirectional storage port, and one isolated load port. The proposed four-port dc/dc converter is derived by simply adding two switches and two diodes to the traditional half-bridge topology. Zero-voltage switching is realized for all four main switches. Three of the four ports can be tightly regulated by adjusting their independent duty-cycle values, while the fourth port is left unregulated to maintain the power balance for the system. Circuit analysis and design considerations are presented; the dynamic modeling and close-loop design guidance are given as well. Experimental results verify the proposed topology and confirm its ability to achieve tight independent control over three power-processing paths. This topology promises significant savings in component count and losses for renewable energy power-harvesting systems.

Implementation and Analysis of an Improved Series-Loaded Resonant DC–DC Converter Operating Above Resonance for Battery Chargers

The well-established advantages of resonant converters, including simplicity of circuit configuration, ease of the control scheme, low switching losses, and low electromagnetic interference, among others, have led to their attracting more interest. This work develops a highly efficient battery charger with an improved series-loaded resonant converter for renewable energy applications to improve the performance of traditional switching-mode charger circuits. The switching frequency of the improved series-loaded resonant battery charger was at continuous conduction mode. Circuit operation modes are determined from the conduction profiles. Operating equations and operating theory are also developed. This study utilizes the fundamental wave approximation and a battery equivalent circuit to simplify the circuit analyses. The mean charging efficiency of the proposed topology is as high as 87.5%.