Byung Duk Min

A Novel Topology for Photovoltaic DC/DC Full-Bridge Converter With Flat Efficiency Under Wide PV Module Voltage and Load Range

In this paper, a novel topology for a photovoltaic (PV) dc/dc converter that can dramatically reduce the power rating and increase the efficiency of a PV system by analyzing PV module characteristics is proposed. Based on the analysis, in the proposed topology, only 30.7% power of the total PV system is needed for a dc/dc converter. Furthermore, the dc/dc converter efficiency curve is flat under wide PV module voltage and all load ranges. In particular, the converter efficiency at the lower duty range is dramatically improved. The total PV system is implemented for a 250-kW PV power conditioning system (PCS). This system has only three dc/dc converters with a 25-kW power rating. It is only one-third of the total PV PCS power. The 25-kW prototype PV dc/dc converter is introduced to experimentally verify the proposed topology. In addition, an experimental result shows that the proposed topology exhibits a good performance.

A novel grid-connected PV PCS with new high efficiency converter

In this paper, new topology is proposed that can dramatically reduce the converter power rating and increase the efficiency of total PV system. Since the output voltage of PV module has very wide voltage range, in general, the DC/DC converter is used to get constant high DC voltage. According to analysis of PV characteristics, in proposed topology, only 20% power of total PV system power is needed for DC/DC converter. DC/DC converter used in proposed topology has flat efficiency curve at all load range and very high efficiency characteristics. The total system efficiency is the product of that of converter and that of inverter. In proposed topology, because the converter efficiency curve is flat all load range, the total system efficiency at the low power range is dramatically improved. The proposed topology is implemented for 200 kW PCS system. This system has only three DC/DC converters with 20 kW power rating each other. It is only one-third of total system power. The experiment results show that the proposed topology has good performance.

Input-Series-Output-Parallel Connected DC/DC Converter for a Photovoltaic PCS with High Efficiency under a Wide Load Range

This paper proposes an input-series-output-parallel connected ZVS full bridge converter with interleaved control for photovoltaic power conditioning systems (PV PCS). The input-series connection enables a fully modular power-system architecture, where low voltage and standard power modules can be connected in any combination at the input and/or at the output, to realize any given specifications. Further, the input-series connection enables the use of low-voltage MOSFETs that are optimized for a very low RDSON, thus, resulting in lower conduction losses. The system costs decrease due to the reduced current, and the volumes of the output filters due to the interleaving technique. A topology for a photovoltaic (PV) dc/dc converter that can dramatically reduce the power rating and increase the efficiency of a PV system by analyzing the PV module characteristics is proposed. The control scheme, consisting of an output voltage loop, a current loop and input voltage balancing loops, is proposed to achieve input voltage sharing and output current sharing. The total PV system is implemented for a 10-㎾ PV power conditioning system (PCS). This system has a dc/dc converter with a 3.6-㎾ power rating. It is only one-third of the total PV PCS power. A 3.6-㎾ prototype PV dc/dc converter is introduced to experimentally verify the proposed topology. In addition, experimental results show that the proposed topology exhibits good performance.

Active Frequency with a Positive Feedback Anti-Islanding Method Based on a Robust PLL Algorithm for Grid-Connected PV PCS

This paper proposes an active frequency with a positive feedback in the d-q frame anti-islanding method suitable for a robust phase-locked loop (PLL) algorithm using the FFT concept. In general, PLL algorithms for grid-connected PV PCS use d-q transformation and controllers to make zero an imaginary part of the transformed voltage vector. In a real grid system, the grid voltage is not ideal. It may be unbalanced, noisy and have many harmonics. For these reasons, the d-q transformed components do not have a pure DC component. The controller tuning of a PLL algorithm is difficult. The proposed PLL algorithm using the FFT concept can use the strong noise cancelation characteristics of a FFT algorithm without a PI controller. Therefore, the proposed PLL algorithm has no gain-tuning of a PI controller, and it is hardly influenced by voltage drops, phase step changes and harmonics. Islanding prediction is a necessary feature of inverter-based photovoltaic (PV) systems in order to meet the stringent standard requirements for interconnection with an electrical grid. Both passive and active anti-islanding methods exist. Typically, active methods modify a given parameter, which also affects the shape and quality of the grid injected current. In this paper, the active anti-islanding algorithm for a grid-connected PV PCS uses positive feedback control in the d-q frame. The proposed PLL and anti-islanding algorithm are implemented for a 250kW PV PCS. This system has four DC/DC converters each with a 25kW power rating. This is only one-third of the total system power. The experimental results show that the proposed PLL, anti-islanding method and topology demonstrate good performance in a 250kW PV PCS.

A Novel Topology for Photovoltaic Series Connected DC/DC Converter with High Efficiency Under Wide Load Range

The paper proposes a new topology for photovoltaic DC/DC converter with high efficiency under wide input voltage range is proposed. Photovoltaic DC/DC is a very crucial part of power conditioning system(PCS). Considering that output characteristic of photovoltaic cell has wide voltage range, depending on the operating conditions of photovoltaic cell, the DC/DC converter also needs to have wide input voltage range to regulate the constant output voltage. In addition, a high rated voltage of power switch (MOSFET) for DC/DC converter is necessary in order to be compatible with the high maximum output voltage of photovoltaic cells maximum output voltage. Also photovoltaic power conditioning system should have a high efficiency under operation condition. To satisfy PV PCS condition series connected non-isolated DC/DC converter topology is proposed. This paper examines the proposed topology employing four modules and shows that it dramatically enhances the energy efficiency from low load to high load condition by reducing the required power level for DC/DC converter by one-third of conventional DC/DC converter. A case of 20 kW prototype as the PV DC/DC converter is introduced to experimentally verify the proposed topology.

A new topology for PV DC/DC converter with high efficiency under wide load range

The paper proposes a new topology for photovoltaic DC/DC converter with high efficiency under wide input voltage range is proposed. Photovoltaic DC/DC is a very crucial part of power conditioning system (PCS). Considering that output characteristic of photovoltaic cell has wide voltage range, depending on the operating conditions of photovoltaic cell, the DC/DC converter also needs to have wide input voltage range to regulate the constant output voltage. In addition, a high rated voltage of power switch (MOSFET) for DC/DC converter is necessary in order to be compatible with the high maximum output voltage of photovoltaic cells maximum output voltage. Also photovoltaic power conditioning system should have a high efficiency under operation condition. To satisfy PV PCS condition series connected non-isolated DC/DC converter topology is proposed. This paper examines the proposed topology employing four modules and shows that it dramatically enhances the energy efficiency from low load to high load condition by reducing the required power level for DC/DC converter by one-third of conventional DC/DC converter. A case of 20 kW prototype as the PV DC/DC converter is introduced to experimentally verify the proposed topology.

A New Topology for Grid-Connected Photovoltaic System Using the Converter with Flat Efficiency Curve for All Load Range

In this paper, new topology is proposed that can dramatically reduce the converter power rating and increase the efficiency of total PV system. Since the output voltage of PV module has very wide voltage range, in general, the DC/DC converter is used to get constant high DC voltage. According to analysis of PV characteristics, in proposed topology, only 20% power of total PV system power is needed for DC/DC converter. DC/DC converter used in proposed topology has flat efficiency curve at all load range and very high efficiency characteristics. The total system efficiency is the product of that of converter and that of inverter. In propose topology, because the converter efficiency curve is flat all load range, the total system efficiency at the low power range is dramatically improved. The proposed topology is implemented for 200 kW PCS system. This system has only three DC/DC converters with 20 kW power rating each other. It is only one-third of total system power. The experiment results show that the proposed topology has good performance.

A Method to Reduce Power Consumption of Active-Clamped Flyback Converter at No-Load Condition

A method for lower power consumption of active-clamped flyback converter at no-load condition is proposed in this study. The active-clamped flyback converter is one of the most well known converters, which can reduce the switching losses and EMI noises. However this converter is more than conventional flyback converter with respect to power consumption in the no-load condition. This is due to high conduction current of resonant converter. To reduce conduction loss at no-load condition, the converter turns off the auxiliary switch and operates only flyback mode. Some experimental results are included to verify the system performances in this paper. The test result showed that the power loss is 0.75 W at no-load condition. This result is the compliance with the European Code of Conduct limits regarding the no-load power consumption

A new topology for photovoltaic 4 series dc/dc converter with high efficiency under wide load range

The paper proposes a new topology for photovoltaic DC/DC converter with high efficiency under wide input voltage range is proposed. Photovoltaic DC/DC is a very crucial part of power conditioning system (PCS). Considering that output characteristic of photovoltaic cell has wide voltage range, depending on the operating conditions of photovoltaic cell, the DC/DC converter also needs to have wide input voltage range to regulate the constant output voltage. In addition, a high rated voltage of power switch (MOSFET) for DC/DC converter is necessary in order to be compatible with the high maximum output voltage of photovoltaic cellpsilas maximum output voltage. Also photovoltaic power conditioning system should have a high efficiency under operation condition. To satisfy PV PCS condition series connected non-isolated DC/DC converter topology is proposed. This paper examines the proposed topology employing four modules and shows that it dramatically enhances the energy efficiency from low load to high load condition by reducing the required power level for DC/DC converter by one-third of conventional DC/DC converter. A case of 25 kW prototype as the PV DC/DC converter is introduced to experimentally verify the proposed topology.

A compact pulse generator using diode opening switch for engine gas treatment application

In this paper a compact pulse generator is proposed for NOx removal system using a corona discharge effect from the exhaust gas of engine cars. A compact pulser based on diodes for opening switches and inductive energy storage has been developed. The pulser consists of a pulse compression circuit including a primary low-voltage stored capacitor, a semiconductor closing switch (a thyristor) as its initial switch, a saturable pulse transformer, and secondary high-voltage circuit including a capacitor, opening diodes, and a resistive load. The experiment results of a proposed pulser with resistance of 200 Omega are following: the voltage amplitude is about 21 kV, the rise time (between 0.1~0.9 of amplitude) is about 21 ns, the pulse width in full width at half maximum (FWHM) is about 42 ns