EPE Association: EPE 2018 - LS3c: Power Supplies

EPE 2018 - LS3c: Power Supplies
You are here: EPE Documents > 01 - EPE & EPE ECCE Conference Proceedings > EPE 2018 ECCE Europe - Conference > EPE 2018 - Topic 07: Power Supplies > EPE 2018 - LS3c: Power Supplies

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   A comparative evaluation of an un-regulated and a regulated input isolated dc-dc converter using WBG devices
By Rakesh RAMACHANDRAN [View]
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Abstract: Power supply systems for low voltage, high current applications often have a front-end ac-dc converterfollowed by an un-regulated input or a regulated input isolated dc-dc converter. This paper illustratesthe design, analysis and comparison of an un-regulated and a regulated input isolated dc-dc converterutilizing wide band-gap (WBG) devices. For the comparison and evaluation, SiC devices are used at theprimary side and GaN devices at the secondary side of the converter. Due to the high voltage (> 650V)requirement at the input side of the dc-dc converter, SiC MOSFETs are selected instead of GaN devices.The analysis reveals that for higher switch efficiency and smaller chip area, it is better to have a regulated input, isolated dc-dc converter. This paper also demonstrates that, by the usage of a regulated input isolated dc-dc converter half the switching power device chip area can be saved compared to an unregulated input dc-dc converter, thereby the cost of the converter can be reduced drastically.

   Decoupling Power Flow Control of Triple-Active Bridge Converter with Voltage Difference between Each Port for Distributed Power Supply System
By Keigo KATAGIRI [View]
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Abstract: An autonomous DC microgrid system that uses a triple-active bridge (TAB) converter as a three-way power routing unit is proposed. In this system, various renewable energies, batteries, and local consumer appliances could be integrated by the three-way power routers with different operating DC voltages, such as 400 V DC bus voltages, 110 V battery systems, and 48 V ICT equipment. Accordingly, the three-way power router has to control the power flow independently among each output port with different operating DC bus voltages. Furthermore, it has to achieve constant current (CC) control or constant voltage (CV) control to satisfy different electrical applications. In this paper, a decoupling power flow control with a voltage difference between each port of the TAB converter is proposed. A prototype of the TAB converter rated at 400 V/400 V/48 V, 10 kW, and 20 kHz operating frequency was implemented to demonstrate the feasibility. In addition, two output ports have a voltage difference and different control targets where port 2 operated in 400 V output voltage and CC control, and port 3 operated in 48 V output voltage and CV control, respectively. The validity of the system was experimentally demonstrated by measuring the step response of the TAB converter. The experimental waveforms of the prototype with a voltage difference show that the CC control and CV control operate normally. Moreover, since the interference between each port was not observed, the control system was proved to be effective when the TAB converter had a voltage difference between each port.

   Improving Robustness Against Variation in Resonance Frequency for Repeater of Resonant Inductive Coupling Wireless Power Transfer Systems
By Masataka ISHIHARA [View]
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Abstract: Intermediate resonators (repeaters) for resonant inductive coupling wireless power transfer have been widely studied as a method of improving not only the transmission distance but also the output power. For the repeater to operate effectively, it is needed to induce a large current in the repeater to enhance the magnetic field far from a transmitting resonator. However, it is often difficult to induce a large current in the repeater due to frequency splitting phenomenon. This phenomenon easily occurs when the resonator having high quality factor such as the repeater is used. The frequency characteristic of the induced current in the repeater has multiple peaks when the frequency splitting phenomenon occurs. In addition, these multiple peaks shift according to slight variation in the parameters of the coil and the capacitor that constitute the resonator. This slight variation is easily caused by production error, temperature characteristic, and aging degradation of the coil and the capacitor. The induced current in the repeater is significantly decreased by the slight variation in the parameters, namely, the slight variation in the resonance frequency. Therefore, the repeater has low robustness against variation in the resonance frequency. To address these difficulties, we apply an auxiliary circuit to the repeater. The auxiliary circuit can dynamically adjust a phase of the induced current in the repeater, namely, the resonance frequency without complicated control. As a result, a large induced current can be maintained even if the frequencies corresponding to the peaks shift. Consequently, we can provide the repeater having a stable characteristic against the variation in the resonance frequency. The effectiveness of the repeater applied the auxiliary circuit and the appropriateness of analysis results are supported with simulation and experimental results.

   Output Voltage Stability of Series Connected Transformers for Isolated Auxiliary Supplies in Modular Medium Voltage Converter Systems
By Simon FUCHS [View]
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Abstract: A common way of implementing MV insulated gate and/or auxiliary power supplies for modular converters is using series connected transformers in an LLC resonant converter topology. The LLC converter can result in output voltage instabilities for differing constant power loads at the outputs when operated at resonance frequency. To balance the output voltages, a new balancing concept based on a coupling between the individual transformers is proposed, which guarantees constant output voltages even for highly unbalanced power consumptions at the outputs. Based on the coupling, a concept for a modular MV isolated auxiliary supply for modular multilevel converters (MMCs) is presented. Simulation and measurement results for the presented concept, as well as a comparison with alternative output voltage balancing solutions are provided.

EPE 2018 - LS3c: Power Supplies
You are here: EPE Documents > 01 - EPE & EPE ECCE Conference Proceedings > EPE 2018 ECCE Europe - Conference > EPE 2018 - Topic 07: Power Supplies > EPE 2018 - LS3c: Power Supplies
	[return to parent folder]

	A comparative evaluation of an un-regulated and a regulated input isolated dc-dc converter using WBG devices By Rakesh RAMACHANDRAN	[View] [Download]
Abstract: Power supply systems for low voltage, high current applications often have a front-end ac-dc converterfollowed by an un-regulated input or a regulated input isolated dc-dc converter. This paper illustratesthe design, analysis and comparison of an un-regulated and a regulated input isolated dc-dc converterutilizing wide band-gap (WBG) devices. For the comparison and evaluation, SiC devices are used at theprimary side and GaN devices at the secondary side of the converter. Due to the high voltage (> 650V)requirement at the input side of the dc-dc converter, SiC MOSFETs are selected instead of GaN devices.The analysis reveals that for higher switch efficiency and smaller chip area, it is better to have a regulated input, isolated dc-dc converter. This paper also demonstrates that, by the usage of a regulated input isolated dc-dc converter half the switching power device chip area can be saved compared to an unregulated input dc-dc converter, thereby the cost of the converter can be reduced drastically.

	Decoupling Power Flow Control of Triple-Active Bridge Converter with Voltage Difference between Each Port for Distributed Power Supply System By Keigo KATAGIRI	[View] [Download]
Abstract: An autonomous DC microgrid system that uses a triple-active bridge (TAB) converter as a three-way power routing unit is proposed. In this system, various renewable energies, batteries, and local consumer appliances could be integrated by the three-way power routers with different operating DC voltages, such as 400 V DC bus voltages, 110 V battery systems, and 48 V ICT equipment. Accordingly, the three-way power router has to control the power flow independently among each output port with different operating DC bus voltages. Furthermore, it has to achieve constant current (CC) control or constant voltage (CV) control to satisfy different electrical applications. In this paper, a decoupling power flow control with a voltage difference between each port of the TAB converter is proposed. A prototype of the TAB converter rated at 400 V/400 V/48 V, 10 kW, and 20 kHz operating frequency was implemented to demonstrate the feasibility. In addition, two output ports have a voltage difference and different control targets where port 2 operated in 400 V output voltage and CC control, and port 3 operated in 48 V output voltage and CV control, respectively. The validity of the system was experimentally demonstrated by measuring the step response of the TAB converter. The experimental waveforms of the prototype with a voltage difference show that the CC control and CV control operate normally. Moreover, since the interference between each port was not observed, the control system was proved to be effective when the TAB converter had a voltage difference between each port.

	Improving Robustness Against Variation in Resonance Frequency for Repeater of Resonant Inductive Coupling Wireless Power Transfer Systems By Masataka ISHIHARA	[View] [Download]
Abstract: Intermediate resonators (repeaters) for resonant inductive coupling wireless power transfer have been widely studied as a method of improving not only the transmission distance but also the output power. For the repeater to operate effectively, it is needed to induce a large current in the repeater to enhance the magnetic field far from a transmitting resonator. However, it is often difficult to induce a large current in the repeater due to frequency splitting phenomenon. This phenomenon easily occurs when the resonator having high quality factor such as the repeater is used. The frequency characteristic of the induced current in the repeater has multiple peaks when the frequency splitting phenomenon occurs. In addition, these multiple peaks shift according to slight variation in the parameters of the coil and the capacitor that constitute the resonator. This slight variation is easily caused by production error, temperature characteristic, and aging degradation of the coil and the capacitor. The induced current in the repeater is significantly decreased by the slight variation in the parameters, namely, the slight variation in the resonance frequency. Therefore, the repeater has low robustness against variation in the resonance frequency. To address these difficulties, we apply an auxiliary circuit to the repeater. The auxiliary circuit can dynamically adjust a phase of the induced current in the repeater, namely, the resonance frequency without complicated control. As a result, a large induced current can be maintained even if the frequencies corresponding to the peaks shift. Consequently, we can provide the repeater having a stable characteristic against the variation in the resonance frequency. The effectiveness of the repeater applied the auxiliary circuit and the appropriateness of analysis results are supported with simulation and experimental results.

	Output Voltage Stability of Series Connected Transformers for Isolated Auxiliary Supplies in Modular Medium Voltage Converter Systems By Simon FUCHS	[View] [Download]
Abstract: A common way of implementing MV insulated gate and/or auxiliary power supplies for modular converters is using series connected transformers in an LLC resonant converter topology. The LLC converter can result in output voltage instabilities for differing constant power loads at the outputs when operated at resonance frequency. To balance the output voltages, a new balancing concept based on a coupling between the individual transformers is proposed, which guarantees constant output voltages even for highly unbalanced power consumptions at the outputs. Based on the coupling, a concept for a modular MV isolated auxiliary supply for modular multilevel converters (MMCs) is presented. Simulation and measurement results for the presented concept, as well as a comparison with alternative output voltage balancing solutions are provided.