Active power decoupling methods are developed to deal with the inherent ripple power at twice the grid frequency in single-phase systems generally by adding active switches and energy storage units. They have obtained a wide range of applications, such as photovoltaic (PV) systems, light-emitting diodes (LEDs) drivers, fuel cell (FC) power systems, and electric vehicle (EV) battery chargers, etc. This paper provides a comprehensive review of active power decoupling circuit topologies. They are categorized into two groups in terms of the structure characteristics: independent and dependent decoupling circuit topologies. The former operates independently with the original converter, and the latter, however, shares the power semiconductor devices with the original converter partially and even completely. The development laws for the active power decoupling topologies are revealed from the view of “duality principle,” “switches sharing,” and “differential connection.” In addition, the exceptions and special cases are also briefly introduced. This paper is targeted to help researchers, engineers, and designers to construct some new decoupling circuit topologies and properly select existing ones according to the specific application.

Review of Active Power Decoupling Topologies in Single-Phase Systems

Методы подавления шумов и помех в электронных системах. (Noise reduction techniques in electronic systems)

Microgrid testbeds around the world: State of art

Advanced electrochemical energy storage devices (EESDs) that can store electrical energy efficiently while being miniature/flexible/wearable/load-bearing are much needed for various applications ranging from flexible/wearable/portable electronics to lightweight electric vehicles/aerospace equipment. Carbon-based fibers hold great promise in the development of these advanced EESDs (e.g., supercapacitors and batteries) due to their being lightweight, high electrical conductivity, excellent mechanical strength, flexibility, and tunable electrochemical performance. This review summarizes the fabrication techniques of carbon-based fibers, especially carbon nanofibers, carbon-nanotube-based fibers, and graphene-based fibers, and various strategies for improving their mechanical, electrical, and electrochemical performance. The design, assembly, and potential applications of advanced EESDs from these carbon-based fibers are highlighted. Finally, the challenges and future opportunities of carbon-based fibers for advanced EESDs are discussed.

Carbon-Based Fibers for Advanced Electrochemical Energy Storage Devices

Various cell architectures of capacitive deionization: Recent advances and future trends.

Direct energy recovery system for membrane capacitive deionization

H-bridge converter with additional switch legs (HA converter) and its offspring circuit are proposed in this paper with the intent to reduce the common mode noise. The proposed topology connects grounds of the input and output terminals, which gives zero common mode current in the ideal case. The operation of the proposed circuit is flexible and allows for the circuit to be capable of both ac–dc and dc–ac conversions. The proposed topology is especially advantageous when it is applied to the photovoltaic power conditioning system in dc distribution system or stand-alone power system because they include large stray capacitances and are prone to common mode EMI. In this paper, a 4-switch HA (HA4S) converter for both ac–dc rectification and dc–ac inversion is derived from the proposed HA converter as the implementation example. The experimental results based on the proposed and the conventional prototype circuits prove that the HA4S converter outperforms the conventional counterparts.

Low-Common Mode Voltage H-Bridge Converter with Additional Switch Legs

This paper describes phase current reconstruction methods from dc-link currents in three-phase three-level PWM inverters. Since the three-level inverters have three paths between dc-link and power switches, the reconstructions differ from that in two-level inverters which have two paths there. Considering these paths in three-level inverter, this paper proposes the methods for phase current reconstruction. While the reconstruction method is executed by the currents sampled on the dc-links, the system encounters current-unmeasurable areas where the dc currents cannot be sampled due to the lack of measurement time according to the PWM status. This paper analyzes the areas and proposes a minimum voltage injection method for minimizing them to guarantee accurate current reconstruction. The method provides the expanded operating areas especially in low-output voltage operation and the minimized distortions in output voltages. The feasibility of the proposed method has been assessed in experiments.

Phase Current Reconstructions from DC-Link Currents in Three-Phase Three-Level PWM Inverters

The single-phase diode rectifier system with small dc-link capacitor shows wide diode conduction time and it improves the grid current harmonics. By shaping the output power, the system meets the grid current harmonics regulation without any power factor corrector or grid filter inductor. However, the system has torque ripple and suffers efficiency degradation due to the insufficient dc-link voltage. To solve this problem, this paper proposes the dc-link shunt compensator (DSC) for small dc-link capacitor systems. DSC is located on dc-node in parallel and operates as voltage source, improving the system performances. This circuit helps the grid current-shaping control during grid-connection time, and reduces the flux-weakening current by supplying the energy to the motor during grid-disconnection time. This paper presents a power control method and the design guideline of DSC. The feasibility of DSC is verified by simulation and experimental results.

Single-Phase Grid-Connected Motor Drive System With DC-Link Shunt Compensator and Small DC-Link Capacitor

This paper proposes grid current shaping method using dc-link shunt compensator for three-phase diode rectifier system without electrolytic dc-link capacitor. In the proposed method, the diode rectifier system can satisfy the grid regulation IEC61000-3-12 without any power factor correction circuit or heavy grid filter inductor. The proposed grid current shaping method can be realized by applying DSC with reduced-rating components and without electrolytic capacitor, which is connected parallel to the dc link. Since DSC has no electrolytic capacitor, the system with DSC has high circuit reliability. Furthermore, DSC can enhance the system efficiency, especially in flux-weakening area, since the motor drive inverter recovers the reduced modulation index, which has been spent in the additional control for small passive components. This paper presents the control method for DSC and analyzes the effect of proposed method. The feasibility of proposed method is verified by simulation and experimental results.

Hojoon Shin

Papers

Direct energy recovery system for membrane capacitive deionization

Low-Common Mode Voltage H-Bridge Converter with Additional Switch Legs

Phase Current Reconstructions from DC-Link Currents in Three-Phase Three-Level PWM Inverters

Single-Phase Grid-Connected Motor Drive System With DC-Link Shunt Compensator and Small DC-Link Capacitor

Grid Current Shaping Method with DC-Link Shunt Compensator for Three-Phase Diode Rectifier-Fed Motor Drive System