High-buck in Buck and High-boost in Boost Dual-Mode Inverter (Hb2DMI)

The application of the dual-mode time-sharing technique in a novel transformerless photovoltaic (PV) inverters is proposed and investigated. The simultaneous high step-down or high step-up conversion with 97.6 % peak efficiency and injected current with THD < 2% is achieved. The leakage current problem, which is a main concern with the transformerless PV inverters, is around 20 mA. The indirect current control, especially at transition modes of operation is highly improved by utilizing a fast dead-beat control scheme. The working principles of the proposed converter show that the step-down and the step-up voltage gains are (D/(1-D)) 2 and D/(1-D) 2 , respectively. Furthermore, a 1 kW, 220 VAC and 200 VDC experimental prototype is implemented to confirm the theoretical achievements.Science Foundation Irelan

An Extendable Quadratic Bidirectional DC-DC Converter for V2G and G2V Applications

This paper proposes an extendable quadratic bidirectional DC-DC converter that has an improved voltage transfer ratio (VTR) with capability of redundancy and modularity for electric vehicle applications. As n modules are embedded, its VTR becomes n times higher for both directions of currents. Furthermore, the common electrical ground between input and output is preserved. This is a simple structure with the lowest rating of semiconductors in the family of quadratic bidirectional converters leading to ease of control ability. The proposed converter performance is evaluated in both power flow direction using the dead-beat controller which is smooth, accurate and fast response. Finally, the process of charging/discharging of a lithium-ion battery is controlled through the proposed converter. A 500 W experimental results are provided in both power flow directions in closed-loop system in the presence of the proposed controller. The obtained results verify the applicability of this structure.Science Foundation Irelan

Improved design of passive damping for single phase grid‐connected LCL filtered inverter considering impedance stability

Abstract Grid‐connected inverters with an inductor–capacitor–inductor (LCL) filter usually require the implementation of damping in the filter to suppress the resonance associated with the filter and hence ensure internal stability. The value for the damping resistor is commonly chosen as one‐third of the capacitive reactance at the resonance frequency of the LCL filter. However, this commonly‐used principle does not take into account the external stability of the inverter, i.e. the potential for an interaction between the inverter output impedance and the grid impedance. This work discusses a new design for the damping resistor to assure the external stability of the voltage source inverter as well as its internal stability. The analysis shows that the proposed design can ensure the external stability of the voltage source inverter with different grid impedances as well as robustness against the variations of the filter parameters while maintaining low power losses and an acceptable attenuation rate for high‐frequency harmonics. To validate the theoretical analysis, a 1 kW, 110 V laboratory prototype is implemented. The obtained results confirm the applicability of the proposed design approach

Bidirectional wide range and high voltage gain buck‐boost DC‐DC converter for EV chargers empowering V2G‐G2V applications

Abstract This paper proposes a new wide range bidirectional buck‐boost dc‐dc converter with improved voltage gain in either forward (discharging) or backward (charging) direction for electric vehicle (EV) applications. The converter has high‐voltage gain ratio with no theoretical limits in the output voltage in both directions, and presents a good balance between the component count, number of conducting components, semiconductor device ratings, having direct connection between input and output terminals, and efficiency which makes it a practical solution for the EV charger levels 1, 2, and 3 power converter unit. The operating principle, steady‐state characteristics including the current and voltage stress of the switches, and comparison with other state of the art dc‐dc bidirectional converters are explained in detail. In order to validate the theoretical analysis, a 500 W, 200 V or 40 V to 180 V laboratory prototype is implemented. The obtained results confirm the applicability of this structure and demonstrate a peak efficiency of 97.2% in the forward and 97.6% in the backward direction modes of operation

Flying‐inductor‐cell based inverters for single‐phase transformerless PV applications

Abstract The application of the general flying‐inductor (FI) cell in two novel transformerless photo‐voltaic (PV) inverters are proposed and investigated. The simultaneous step up and down ability is possible with both topologies, while a high conversion efficiency and a high‐quality AC current are achieved. The leakage current problem, which is a main concern with the transformerless PV inverters, is also considered. One of the proposed topologies presents a higher efficiency, while the other one provides the high quality of injected current with the lowest number active switches. The current control, especially at transition modes of operation is highly improved by utilizing a fast response dead‐beat control scheme. The working principles of the proposed converters are explained in details and 0.88‐kW experimental prototypes are implemented to confirm the theoretical achievements. Finally, a comparison with other existing topologies has been investigated for better clarification of the advantages and disadvantages of the proposed inverters