EPE Association: EPE 2011 - LS4b: Topic 15: Converter Topologies for Renewable Energy Sources

EPE 2011 - LS4b: Topic 15: Converter Topologies for Renewable Energy Sources
You are here: EPE Documents > 01 - EPE & EPE ECCE Conference Proceedings > EPE 2011 ECCE Europe - Conference > EPE 2011 - Topic 15: Non-rotating power generation and storage systems > EPE 2011 - LS4b: Topic 15: Converter Topologies for Renewable Energy Sources

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   Comparison of 3 Self-Starting Step-Up DC:DC Converter Topologies for Harvesting Energy from Low-Voltage and Low-Power Microbial Fuel Cells
By Nicolas DEGRENNE, Bruno ALLARD, Francois BURET, Florent MOREL [View]
[Download]

Abstract: This paper describes and evaluates 3 original step-up converter architectures able to harvest energy from low-voltage and low-power generators. Design and sizing are made according to specifications issued from the stringent characteristics of microbial fuel cells. The maximum harvested power is10mW under input voltage Vin=0.3V (33mA input current). The considered converters include self-oscillating circuits for autonomous operation. The 2 first topologies are respectively adapted fromboost and flyback topologies. The 3rd topology uses a Greinacher voltage-lift circuit. Energy istransferred to the load both directly (forward transfer) and indirectly (flyback transfer). PSPICEsimulations enable evaluation and comparison of the 3 topologies in term of efficiency, robustness,step-up ratio, control and cost. Best efficiency of 80.6\% is achieved by the boost-derived circuit whichalso enables a feedback action to harvest energy at maximum power point.

   Dynamic Properties of PCM-Controlled Current-Fed Boost Converter in Photovoltaic System Interfacing
By Jari LEPPAAHO, Teuvo SUNTIO [View]
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Abstract: The interfacing of photovoltaic (PV) energy source is known to be problematic due to the highly varying terminal characteristics of the energy harvesting unit, generally a PV generator. Therefore, its power flow needs to be regulated and a certain maximum power point (MPP) traced. The switched-mode dc-dc converters are conventionally used to interface energy sources possessing constant-voltage nature. These voltage-fed (VF) converters have been used as a basis for the MPP-tracking devices as well. It is observed, however, that the performance of such converter is not optimal in this purpose, because the PV generator possesses a current-source nature. Therefore, an additional capacitor is usually added between the source and the converter to enhance the constant-voltage properties of the source. The PV regulation is also performed by controlling the input voltage. These modifications change, however, the VF converter into a current-fed (CF) converter, which has totally different static and dynamic behavior than the original converter. This implicit duality transformation also causes a situation, where the usage of conventional inner-loop control, such as peak-current-mode (PCM) control, may lose its beneficial nature or the converter may even cease to operate in a stable manner. This paper analyses the static and dynamic properties of the buck-derived PV converter known as a dual or CF boost converter under the input-voltage and PCM controls. Investigations show that the conventional PCM control is not recommended to be used in the CF converters due to its inherent VF properties.

   Interleaved High Step-Up Converter with Built-In Transformer and Voltage Doubler for PV Grid-connected Generation Systems
By Weichen LI, Wuhua LI, Wenfeng CUI, Yi ZHAO, Bo YANG, Xiangning HE [View]
[Download]

Abstract: In this paper, a zero voltage transition (ZVT) interleaved high step-up converter with built-in transformer and voltage doubler for photovoltaic (PV) grid-connected generation system is proposed. The built-in transformer and the voltage doubler are employed to extend the voltage gain, reduce the switch voltage stress, which makes the low on-resistance switch can be adopted to reduce the conduction losses. The active clamp circuit is employed to recycle the leakage inductance energy of the built-in transformer and to absorb the turn-off voltage spikes on the main switches. Furthermore, zero voltage switching (ZVS) performance is achieved for both the main switch and the clamp switch during the whole switching transition, which can reduce the switching losses. In addition, the reverse-recovery problem of the output diode and the double voltage diode is alleviated by the leakage inductance of the built-in transformer, which can reduce the reverse-recovery losses. Due to the factors mentioned above, the proposed converter is suitable for the high step-up and high power applications. Finally, a 1kW prototype of the PV grid-connected generation system is built to demonstrate the effectiveness of the proposed converter in high step-up and high power applications.

EPE 2011 - LS4b: Topic 15: Converter Topologies for Renewable Energy Sources
You are here: EPE Documents > 01 - EPE & EPE ECCE Conference Proceedings > EPE 2011 ECCE Europe - Conference > EPE 2011 - Topic 15: Non-rotating power generation and storage systems > EPE 2011 - LS4b: Topic 15: Converter Topologies for Renewable Energy Sources
	[return to parent folder]

	Comparison of 3 Self-Starting Step-Up DC:DC Converter Topologies for Harvesting Energy from Low-Voltage and Low-Power Microbial Fuel Cells By Nicolas DEGRENNE, Bruno ALLARD, Francois BURET, Florent MOREL	[View] [Download]
Abstract: This paper describes and evaluates 3 original step-up converter architectures able to harvest energy from low-voltage and low-power generators. Design and sizing are made according to specifications issued from the stringent characteristics of microbial fuel cells. The maximum harvested power is10mW under input voltage Vin=0.3V (33mA input current). The considered converters include self-oscillating circuits for autonomous operation. The 2 first topologies are respectively adapted fromboost and flyback topologies. The 3rd topology uses a Greinacher voltage-lift circuit. Energy istransferred to the load both directly (forward transfer) and indirectly (flyback transfer). PSPICEsimulations enable evaluation and comparison of the 3 topologies in term of efficiency, robustness,step-up ratio, control and cost. Best efficiency of 80.6\% is achieved by the boost-derived circuit whichalso enables a feedback action to harvest energy at maximum power point.

	Dynamic Properties of PCM-Controlled Current-Fed Boost Converter in Photovoltaic System Interfacing By Jari LEPPAAHO, Teuvo SUNTIO	[View] [Download]
Abstract: The interfacing of photovoltaic (PV) energy source is known to be problematic due to the highly varying terminal characteristics of the energy harvesting unit, generally a PV generator. Therefore, its power flow needs to be regulated and a certain maximum power point (MPP) traced. The switched-mode dc-dc converters are conventionally used to interface energy sources possessing constant-voltage nature. These voltage-fed (VF) converters have been used as a basis for the MPP-tracking devices as well. It is observed, however, that the performance of such converter is not optimal in this purpose, because the PV generator possesses a current-source nature. Therefore, an additional capacitor is usually added between the source and the converter to enhance the constant-voltage properties of the source. The PV regulation is also performed by controlling the input voltage. These modifications change, however, the VF converter into a current-fed (CF) converter, which has totally different static and dynamic behavior than the original converter. This implicit duality transformation also causes a situation, where the usage of conventional inner-loop control, such as peak-current-mode (PCM) control, may lose its beneficial nature or the converter may even cease to operate in a stable manner. This paper analyses the static and dynamic properties of the buck-derived PV converter known as a dual or CF boost converter under the input-voltage and PCM controls. Investigations show that the conventional PCM control is not recommended to be used in the CF converters due to its inherent VF properties.

	Interleaved High Step-Up Converter with Built-In Transformer and Voltage Doubler for PV Grid-connected Generation Systems By Weichen LI, Wuhua LI, Wenfeng CUI, Yi ZHAO, Bo YANG, Xiangning HE	[View] [Download]
Abstract: In this paper, a zero voltage transition (ZVT) interleaved high step-up converter with built-in transformer and voltage doubler for photovoltaic (PV) grid-connected generation system is proposed. The built-in transformer and the voltage doubler are employed to extend the voltage gain, reduce the switch voltage stress, which makes the low on-resistance switch can be adopted to reduce the conduction losses. The active clamp circuit is employed to recycle the leakage inductance energy of the built-in transformer and to absorb the turn-off voltage spikes on the main switches. Furthermore, zero voltage switching (ZVS) performance is achieved for both the main switch and the clamp switch during the whole switching transition, which can reduce the switching losses. In addition, the reverse-recovery problem of the output diode and the double voltage diode is alleviated by the leakage inductance of the built-in transformer, which can reduce the reverse-recovery losses. Due to the factors mentioned above, the proposed converter is suitable for the high step-up and high power applications. Finally, a 1kW prototype of the PV grid-connected generation system is built to demonstrate the effectiveness of the proposed converter in high step-up and high power applications.