Yujin Song

A new soft switching technique for bi-directional power flow, full-bridge DC-DC converter

This paper proposes a new soft switching technique for the phase-shift controlled bi-directional DC-DC converter. The described converter employs a low profile high frequency transformer and two active full-bridge converters for bidirectional power flow capability. A new soft switching technique is proposed, which guarantees soft switching over wide range (no load to full load) without any additional circuit components. In the proposed switching scheme, the switch pairs in the diagonal position of the converter each are turned on/off simultaneously by the switching signals with a variable duty ratio depending on the phase shift amount, and the converter is operated without freewheeling interval. The load range for soft switching is analyzed mathematically and verified by experiments.

Active clamped three-phase isolated boost converter with series output connection for high step-up applications

A new active clamped three-phase isolated boost converter is presented for the high step-up DC-DC converter applications such as fuel cells, photovoltaic and battery sourced power conversion systems. The proposed converter employs the parallel three-phase input and series output structure to handle the high input current and high output voltage. This structure is suitable for generating the high output voltage using relatively low PWM duty and transformer turns ratios, which provides the high efficiency and low device stress. Moreover, the zero voltage switching (ZVS) is also achieved using an active clamping circuit. The operational principle and key waveforms of the proposed converter are presented. The considerations for the design and implementation are also discussed. The experimental results for a prototype converter with a 600W power rating, 24V/380V input/output voltages are provided to show the validity of the proposed converter scheme.

Active clamped three-phase isolated boost converter with voltage doubler output for high voltage conversion ratio

A new active clamped three-phase isolated boost converter is proposed for low voltage distributed energy resources. The proposed converter has a parallel input and voltage doubler output structure to obtain the high output voltage from the low voltage source. The three-phase parallel input structure with an interleaved operation provides a high power rating and reduced input current ripple. The high voltage conversion ratio can be easily obtained using the voltage doubler output stage. Moreover, the zero voltage switching (ZVS) is also achieved using an active clamping circuit. The converter operation and prototype design are presented. The experimental results are finally provided to show the validity of the proposed converter scheme.

Design of power conversion system for Stirling engine Micro-CHP integrated into DC power distribution network

This paper describes a design of the power conversion system for the DC distribution network with the String engine micro-CHP source. The design of the PWM AC-DC and high step-up DC-DC power converters is presented for the Stirling engine with a permanent magnet synchronous generator (PMSG). The maximum power control for a low voltage PMSG and PWM AC-DC converter is discussed and the high efficiency design of the high step-up isolated DC-DC converter is considered. The prototype converter with 1kW power rating and 400VDC output is implemented and the experimental results are provided to verify its operation and performance.

FPGA-based digital current mode controller for phase-shifted full-bridge PWM converter

This paper deals with a digital current mode controller for a phase-shifted full-bridge PWM converter (PSFBC) using a field programmable gate arrays (FPGA). The proposed digital controller consists of a digital PWM generator with a switching frequency of 195 kHz and an average current mode controller based on the discrete-time domain model, which is implemented in a fully hardware manner using a single chip FPGA. The design and implementation method of the proposed digital controller is discussed in this paper. The experimental results are provided to show the validity of the proposed PSFBC with the FPGA-based digital controller.

Grid-Connected Control of Hybrid Energy Storage

This paper deals with a control method for a hybrid energy storage system (ESS) with a battery and super capacitor for grid-connected operation. To improve the grid regulation and to minimize the depth of discharge of the battery, control algorithms for the hybrid ESS are proposed. A p-q control with predictive current control is used for the inverters for the super-capacitor and the battery. To verify the effectiveness of the proposed control method, simulation studies using the PSIM and RTDS are carried out for the actual grid model.