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In this paper, we report on the results of controlling the state of charge (SOC) of batteries for back-up use by using weather forecasts in order to improve the self-consumption rate and store power for back-up. Regarding battery systems for utilizing variable renewable energy and back-up use, we suggest a method for charging and discharging batteries positively by changing the back-up capacity depending...
In this paper, we report various methods for classifying faults that use the data of string measurement devices used for continuously monitoring solar power panels remotely. Low power generation of solar panels is caused not only by panels being broken but also by shadows cast by structures, weeds, etc. If these failures can be classified by using the data of remote string measurement devices, it...
In this paper, we report on a method of finding lot defects and the results of a verification related to the maintenance of power-supply and air-conditioning equipment for ICT. We built a logic and models to automatically detect equipment that may be included in a defective lot. An equipment anomaly analysis system was constructed. For verification, actual past lot failure equipment was applied to...
A numerical analysis of the minimum storage battery capacity required to achieve a certain energy self-consumption rate in a power distribution system that combines solar power generation and a storage battery shows that a DC supply can reduce the required storage battery capacity by about 10% relative to an AC supply by increasing the energy self-consumption rate.
The amount of energy consumed by data centers and telecom buildings is increasing annually due to the buildup and high-density arrangement of ICT equipment, which is needed to handle the rapid rise in traffic brought on by the spread of smartphones and advances in the Internet usage environment. The NTT Group, whose business activities are centered about ICT services, uses approximately 8.5 billion...
In Japan, the liberalization of the electricity retail market is starting in April 2016. Consumers will be able to choose the retail electric suppliers from which to buy. In Germany which domestic electricity market was fully liberalized in 1998, Stadt Werke (local power companies) has maintained more than 20% of the retail electric market share. We studied the feasibility of a regional energy business...
Power consumption of the ICT sector of information and communication facilities and data centers has grown, and this has led to a need to improve energy efficiency of these facilities. DC distribution systems employing 380 VDC as the supply voltage is one promising approach to address this problem, countries around the world and are progressing to develop and deploy commercial services. We demonstrated...
We are currently investigating the specifications of the architecture and control method of a DC power system with photovoltaics and fuel cells that achieves longer power-supply time with limited stockpiling-energy without grid power. For this paper, we focused on the case in which electric power needs to be constantly supplied to a load but photovoltaic power generation is unstable. We applied (1)...
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 February 2014, the NTT Group officially announced that it has launched a high voltage direct current (HVDC) (380-VDC) with a 4-MW-scale power supply system for the Tokyo metropolitan area. Activities, such as international standardization, has led to the commercial commencement of a full-fledged 380-VDC power supply system, demonstration projects, and technology development, which took more than...
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...
It is difficult to repair equipment in a short time after a strong earthquake. Therefore, the power supply to shelters becomes problematic. To solve this problem, a small-scale power system without being dependent on commercial power supplies is needed. We experimentally investigated a power supply system that includes photovoltaic and fuel cells to solve the above-mentioned problem. In this paper,...
We discuss the advantage of highly efficient and reliable higher-voltage direct current (HVDC) power feeding systems and the standardization activities for the power interface conditions in ICT equipment. With the recent spread of Internet services, the power consumption of ICT services is increasing annually. Many data center servicers want to decrease the power consumption of ICT equipment, cooling...
This paper describes the configurations of semiconductor circuit breakers we developed for higher-voltage direct-current (HVDC) power feeding systems. Semiconductor breakers have some merits. The shutdown parts of the breakers are compact and can be controlled remotely. In addition, they do not need to be replaced after shutting down a short circuit. When semiconductor breaker shutdown overcurrent...
This paper describes a molded-cased circuit breaker (MCCB) for higher voltage direct current (HVDC) power feeding systems. To protect circuits from fault current, such as an overcurrent or a short circuit current, an overcurrent circuit breaker is installed in power feeding systems. When a large-scale overcurrent circuit breaker is required, the case which uses MCCBs in HVDC power feeding system can...
400VDC is becoming a new voltage interface for telecommunication buildings and data centers as well as for ICT equipment. 400VDC interface covers applications for up to 400VDC with a typical nominal voltage of 380VDC. Key drivers for utilizing a higher DC voltage are overall efficiency and reliability gains vs present solutions. However, introduction of a new 400VDC interface brings up some questions...
This paper describes a semiconductor breaker for higher-voltage direct-current (HVDC) power feeding systems. To reduce energy consumption of ICT devices, one effective measure is to manage their power use. To manage the power of individual ICT devices, circuit breakers, which turn ICT device power on and off, must be compact and remote-controllable. Because feeding voltage fluctuations, which occur...
This paper describes an operation control method for fuel cell/battery hybrid power supply systems and a state of charge (SOC) estimation method to simulate their operation. Quickly charging or discharging batteries can compensate for demand load power fluctuation, but battery management is essential in these hybrid power supply systems. In this study, a control method for maintaining a constant value...
The purpose of this paper is to present the dynamic characteristics of the new high performance auto-tuning digital control circuit for buck-boost converter when the step change of the load resistance R from 20 Ω to 10Ω. The buck-boost dc-dc converter is used with wide input voltage changing. At the same time, the suitable proportional gain and bias value are changing against the input voltage and...
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