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DC microgrid has been drawing much attention in recent years. In DC microgrid, introduction of renewable energies to demand sides possibly causes power imbalance and reverse power flows on feeders. These problems cause increase of distribution losses and voltage rises in feeders. To overcome these problems, a power flow control method among multiple DC feeders (nodes) is required. We have studied...
This paper studies efficiency improvement of DC power network by using multi-terminal power flow controller (MTPFC). We have proposed MTPFC for flexible and precise power flow control in DC power networks. The circuit topology and the control method have been investigated and it has been clarified that MTPFC is effective for power flow control in DC power networks. In this paper, we address efficiency...
Carrier-spin dynamics in GaAs quantum disks (QD) fabricated by top-down lithography using bio-templates were investigated by means of reflection-type spin-resolved pump-probe spectroscopy. The temperature dependence of electron-spin relaxation time (τs) is found to obey τs ∝ T−3 above 100 K, indicating spin-loss in the barrier due to thermal redistribution of the electron between the QDs and barrier.
To promote the widespread use of HVDC power supply systems, this paper proposes high-efficiency downsized power conversion (380 V to −48 V) equipment for HVDC use having a size small enough for mounting in the dead space of a rack and describes its performance. Configuring 380 V/−48 V conversion equipment with existing technology lowers the efficiency of the entire power supply system and increases...
A new power supply topology is proposed for using various types of power supply systems together in data centers and telecom buildings. In this topology, the power supply chain from the building power receiving point to the IC chips in the ICT equipment is organized into blocks to simplify the number of DC bus conversion steps. Two types of voltage for the DC bus are proposed; 380 V and 48 V. This...
We describe how inrush current flowing into an electromagnetic interference (EMI) filter when ICT equipment is connected to an HVDC system affects the operation of other currently connected ICT equipment. When ICT equipment is connected to an HVDC system, inrush current flows to the EMI filter of newly connected ICT equipment. The inrush current causes voltage oscillation at the input of other (previously...
This paper describes the highly efficient and highly reliable HVDC power supply system that the NTT Group has developed and introduced. We also summarize a technical requirement which is published by NTT, and we built the NTT Group's strategy for HVDC systems implementation. Moreover, we describe a new power supply system concept in order to further reduce power consumption and cost. This system can...
In Japan, human shaped service robots have rarely become commercial products so far and have not been widely utilized in actual fields. The reason is that people cannot determine clear objective for using these robots, and hence its usefulness or necessity are not valued. To clear these doubts, we have experimentally introduced a human shaped service robot to a shopping center, and clarified its benefits...
This paper presents a new digital load-dependent soft-start method of dc-dc converter for energy management system. The soft-start operation is used to prevent negative effects for a power supply. In the conventional soft-start operation, the dc-dc converter must start up very slowly to deal with the worst load condition. It takes long time to start up a power supply. The proposed digital control...
The economic efficiency of photovoltaic (PV) and battery systems for residential power distribution is evaluated quantitatively for the first time under a rate system using electricity prices that change at hourly intervals (i.e., real-time pricing, RTP). The evaluation model assumes that the option price of a feed-in tariff (FIT) decreases continuously. The proposed operational method focuses on...
The purpose of this paper is to present the demonstration of digitally controlled peak current mode parallel dc-dc converter for the higher voltage direct current (HVDC) system. The peak current mode control circuit is only composed of the RC integrator and comparator. It can detect the peak current in real time. A prototype uses 800W phase-shifted full-bridge zero volt switching (ZVS) dc-dc converter...
The purpose of this paper is to present a novel digital peak current mode dc-dc converter and its control characteristics. The proposed method can detect the peak current in real time. The proposed peak current detection circuit is composed of RC integrator and comparator as the A-D converter. The design of RC integrator has a large effect on regulation characteristics and the transient response of...
The purpose of this paper is to present performance characteristics of a quick response digital peak-current-mode 380V dc-dc converter for the green IT system. A proto-type is constructed as the digital control dc-dc converter used in the higher voltage direct current (HVDC) system for the green IT. The proto-type uses the digital peak-current-mode control to show a superior transient response. A...
This paper presents a fast response digitally controlled full bridge converter in parallel operation. The digital controlled circuit has some problem. One of the main problems is the delay time. The delay time includes the conversion time of A-D converter and processing time of digital controller. It exerts a bad influence on the dynamic characteristic. In the proposed method, the sample timing for...
In recent years, 380Vdc distribution systems have been expected to be one of the energy saving solutions for telecommunication buildings and data centers. However, DC distribution systems have various problems. In this paper, We report the results of an investigation of inrush current, including current size, effects and testing methods, as one problem in the construction and operation of 380Vdc power...
The purpose of this paper is to present a new digital control switching power supply for the HVDC system in data center. The two stage converters are proposed to address the problem of input voltage drop. It consists of the boost converter and the phase-shifted full bridge converter. Since the first stage boost converter make the output voltage constant, good regulation characteristics against the...
This paper presents a new digital peak current mode dc-dc converter using a FPGA delay circuit and a simple A-D converter. The peak current detection circuit is only composed of RC integrator and field programmable gate array (FPGA) delay circuit. The sampling point of detected current is changed by the feedback value of output voltage. The RC integrator is performed as the A-D converter for the current...
This paper presents a novel digital P-I-D control FPGA for a switching power supply in the higher voltage direct-current (HVDC) power feeding system. At first, digital fast P control buck type converter is presented. Then, the appropriate number of sample point is determined. Then the fast P control is applied to the full bridge converter for HVDC. The acceptable delay time, with realizing superior...
This paper presents the performance of novel digital P-I-D control switching power supply with fast proportional control, which is compared with conventional digital control. The transient response is improved, while the transient response of proposed method is improved even with P-I-D parameters that are same to the conventional method. It is confirmed that it has the superior transient response,...
This paper presents a novel 800W proto type digital P-I-D control switching power supply for the high voltage direct-current(HVDC) power feeding system The digital control circuit for HVDC power feeding system has some problems. Especially, the conversion time of A-D converter and the processing time of digital controller exert a bad influence upon the dynamic characteristics. In the proposed method,...
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