Shih Ming Chen

A Safety Enhanced, High Step-Up DC–DC Converter for AC Photovoltaic Module Application

Within the photovoltaic (PV) power-generation market, the ac PV module has shown obvious growth. However, a high voltage gain converter is essential for the modules grid connection through a dc-ac inverter. This paper proposes a converter that employs a floating active switch to isolate energy from the PV panel when the ac module is off; this particular design protects installers and users from electrical hazards. Without extreme duty ratios and the numerous turns-ratios of a coupled inductor, this converter achieves a high step-up voltage-conversion ratio; the leakage inductor energy of the coupled inductor is efficiently recycled to the load. These features explain the modules high-efficiency performance. The detailed operating principles and steady-state analyses of continuous, discontinuous, and boundary conduction modes are described. A 15 V input voltage, 200 V output voltage, and 100 W output power prototype circuit of the proposed converter has been implemented; its maximum efficiency is up to 95.3% and full-load efficiency is 92.3%.

A Boost Converter With Capacitor Multiplier and Coupled Inductor for AC Module Applications

The grid-connected AC module is an alternative solution in photovoltaic (PV) generation systems. It combines a PV panel and a micro-inverter connected to grid. The use of a high step-up converter is essential for the grid-connected micro-inverter because the input voltage is about 15 V to 40 V for a single PV panel. The proposed converter employs a Zeta converter and a coupled inductor, without the extreme duty ratios and high turns ratios generally needed for the coupled inductor to achieve high step-up voltage conversion; the leakage-inductor energy of the coupled inductor is efficiently recycled to the load. These features improve the energy-conversion efficiency. The operating principles and steady-state analyses of continuous and boundary conduction modes, as well as the voltage and current stresses of the active components, are discussed in detail. A 25 V input voltage, 200 V output voltage, and 250 W output power prototype circuit of the proposed converter is implemented to verify the feasibility; the maximum efficiency is up to 97.3%, and full-load efficiency is 94.8%.

Novel Isolated High-Step-Up DC–DC Converter With Voltage Lift

A novel two-switch high-step-up isolated converter with voltage lift is proposed in this paper. The proposed isolated converter utilizes a transformer with low turn ratio to achieve high step-up gain. The secondary winding charges two boosting capacitors in parallel as switches during the switch-on period, and two boosting capacitors are discharged in series during the switch-off period. Thus, the converter has high voltage gain with appropriate duty ratio. In addition, by using two clamping diodes and a capacitor on the primary side, leakage energy is recycled, and the voltage spikes of the two active switches are clamped, thereby improving conversion efficiency. Finally, experimental results based on a prototype implemented in the laboratory with an input voltage of 24 V, an output voltage of 200 V, and an output power of 200 W verify the performance of the proposed isolated converter; full-load efficiency is nearly 93%.

Design, Analysis, and Implementation of Solar Power Optimizer for DC Distribution System

This paper proposes a high step-up solar power optimizer (SPO) that efficiently harvests maximum energy from a photovoltaic (PV) panel then outputs energy to a dc-microgrid. Its structure integrates coupled inductor and switched capacitor technologies to realize high step-up voltage gain. The leakage inductance energy of the coupled inductor can be recycled to reduce voltage stress and power losses. A low voltage rating and low-conduction resistance switch improves system efficiency by employing the incremental conductance method for the maximum power point tracking (MPPT) algorithm. Because of its high tracking accuracy, the method is widely used in the energy harvesting of PV systems. laboratory prototypes of the proposed SPO that have an input voltage range of 20 to 40xa0V and a maximum PV output power of 400xa0V/300xa0W are applied. The highest PV power conversion efficiency is 96.7%. The maximum MPPT accuracy is 99.9%, and the full load average MPPT accuracy is 97.8%.

A Novel Switched-Coupled-Inductor DC–DC Step-Up Converter and Its Derivatives

This paper presents a novel dc-dc converter configuration, which successfully integrates two technologies, including a switched capacitor and a switched coupled inductor, into one converter. By adopting a coupled inductor to charge a switched capacitor, the voltage gain can be effectively increased, and the turns ratio of the coupled inductor can be also reduced. Not only lower conduction losses but also higher power conversion efficiency is benefited from a lower part count and lower turns ratios. The proposed converter is simply composed of six components, which can be further derived to varied converters for different purposes, such as a bidirectional converter. The operating principle and steady-state analysis are discussed in this paper. A 250-W laboratory hardware prototype is completed and verified. The voltage gain is up to 11. The highest efficiency is 97.2%, and the full-load efficiency is kept at 93.6%.

Analysis, Design, and Implementation of a Bidirectional Double-Boost DC–DC Converter

This paper presents a new bidirectional dc-dc converter with a high conversion ratio for renewable energy systems. The coupled-inductor technique is used to achieve a high conversion ratio with very simple control circuits. In discharging mode, the converter acts as a two-stage boost converter, controlling one power switch to achieve high-voltage step-up conversion. In charging mode, the converter acts as two cascaded buck converters that control two power switches simultaneously to achieve high-voltage step-down conversion. The operating principles and analysis of the steady-state characteristics are discussed in great detail. Finally, a 24-V/200-V prototype circuit with output power of 200 W is implemented to verify the feasibility of the proposed converter. The maximum efficiency levels in discharging and charging modes are about 94.3% and 91.6%, respectively.

A Simple Implementation of Nonlinear-Carrier Control for Power Factor Correction Rectifier With Variable Slope Ramp on Field-Programmable Gate Array

This paper presents an algorithm for implementing the nonlinear-carrier (NLC) control method for a single-phase power factor correction (PFC) rectifier without an input voltage-sensing circuit, an error amplifier in the current shaping loop, or other external control components. Unity power factor and low harmonic distortion are achieved by adapting NLC control with a variable slope ramp. This ramp is created through a slope comparison without any dividers. The proposed method not only achieves a high power factor, but also efficiently simplifies complexity of integrated circuit realization. A 400-W PFC boost rectifier is implemented to verify the performance of the proposed NLC control. The highest power factor reaches to 99.9% with input voltage of 120 V/60 Hz, and the lowest input current harmonic distortion is 4.267%.

Design and Implementation of a Novel Multilevel DC–AC Inverter

In this paper, a novel multilevel dc-ac inverter is proposed. The proposed multilevel inverter generates seven-level ac output voltage with the appropriate gate signals design. Also, the low-pass filter is used to reduce the total harmonic distortion of the sinusoidal output voltage. The switching losses and the voltage stress of power devices can be reduced in the proposed multilevel inverter. The operating principles of the proposed inverter and the voltage balancing method of input capacitors are discussed. Finally, a laboratory prototype multilevel inverter with 400-V input voltage and output 220 Vrms/2 is implemented. The multilevel inverter is controlled with sinusoidal pulse-width modulation (SPWM) by TMS320LF2407 digital signal processor (DSP). Experimental results show that the maximum efficiency is 96.9% and the full load efficiency is 94.6%.

A novel sinusoidal boost-flyback CCM/DCM DC-DC converter

This paper proposed a novel and simple sinusoidal boost-flyback continuous conduction mode (CCM) converter. This converter continuously produces half-sinusoidal voltage to a line frequency DC-AC inverter. This simple boost-flyback structure utilizes a coupled inductor to achieve a wider voltage gain range. The leakage inductance energy of the coupled inductor can be recycled to reduce the voltage stress and power losses. Consequently, the low-voltage rating and low-conduction resistance switch can be selected to reduce conduction losses and improve system efficiency. The magnetizing inductance of the coupled inductor is operated under CCM, and thus, the harmonic content of the output current is reduced. Finally, a 300 W prototype was implemented for feasibility verification. The maximum efficiency is 97.2%, and the full load efficiency is 96.2%. To verify its AC performance, the proposed converter has connected to a full bridge DC-AC inverter to simulate a micro inverter system with the highest efficiency of 96% and 94.5%under full load condition. The output current total harmonic distortion is 1.3%.

A isolated bidirectional interleaved flyback converter for battery backup system application

This paper proposes a novel isolated bidirectional converter, which can efficiently transfer energy between 400 V DC micro grid and 48 V DC batteries. The proposed structure includes primary windings of two flyback transformers, which are connected in series and sharing the high DC micro grid voltage equally, and secondary windings, which are connected in parallel to batteries. Few decoupling diodes are added into the proposed circuit on both sides, which can let the leakage inductance energy of flyback transformers be recycled easily and reduce the voltage stress as well as power losses during bidirectional power transfer. Therefore, low voltage rating and low conduction resistance switches can be selected to improve system efficiency. A laboratory prototype of the proposed converter with an input/output nominal voltage of 400 V/48 V and the maximum capacity of 500 W is implemented. The highest power conversion efficiency is 93.1 % in step-down function, and near 93 % in step-up function.