Kandenko Co.

Tokyo, Japan

Kandenko Co.

Tokyo, Japan
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Sakai K.,Kandenko Co. | Yamamoto K.,Chubu University
2013 International Symposium on Lightning Protection, SIPDA 2013 | Year: 2013

The lightning damages increases in Photovoltaic (PV) systems because those are usually set up at the place where few tall structure around it. Therefore, it becomes important to establish lightning protection methods. When a lightning occurred near a PV system, the PV modules have the induction overvoltage due to the lightning. As a result, the power conditioner connected to the PV modules may break down due to the induction overvoltage. The overvoltage depends on the set-up conditions of each PV system and the wirings. The overvoltage must be examined on each PV system. In this paper, the overvoltage occurred in DC wirings are measured when the surge current was injected into a frame of a PV array. Furthermore, the level of the overvoltage and generation mechanisms of the overvoltage was researched. © 2013 IEEE.


Sakakibara H.,Kandenko Co. | Hiroi H.,Kandenko Co. | Yamamoto K.,Chubu University
IEEJ Transactions on Power and Energy | Year: 2014

When a lightning strikes a building, potential difference may occur between different class grounding electrodes. Due to the potential difference, electrical equipment inside the building might break down or malfunction. Therefore, it is important to estimate the level of lightning overvoltage as accurately as possible and establish protection methodologies. In this paper, lightning overvoltage between grounding of a building and an individual grounding is discussed by experiments using a 1/10 reduced-scale model and the FDTD (Finite Difference Time Domain) method. © 2014 The Institute of Electrical Engineers of Japan.


Miyamoto Y.,Kandenko Co. | Hayashi Y.,Waseda University
Conference Record of the IEEE Photovoltaic Specialists Conference | Year: 2013

There is a danger of output suppression of high-penetration residential PV systems due to voltage increase. It is necessary to install new technology to prevent the occurrence of such phenomenon. Therefore, we focused our attention on heat pump water heaters (HPWHs). HPWHs are usually used to heat water during night time because electricity prices are cheaper than during the daytime for the load leveling in Japan. So they can be used as a countermeasure without additional cost if they are operated during the daytime. However, HPWHs do not have sufficient capacity to absorb inverse energy at each residence. Thus HPWH operation must be optimized to minimize output suppression loss. In this research, we selected three typical sunny days in spring, autumn and winter. The optimal HPWH operation was calculated by numerical simulation. © 2013 IEEE.


Miyamoto Y.,Kandenko Co. | Hayashi Y.,Waseda University
IEEE PES Innovative Smart Grid Technologies Conference Europe | Year: 2012

There is a danger of power generation efficiency decreasing due to voltage increase when clustered residential PV systems are grid-interconnected to a single distribution line. As a countermeasure, installation of the reactive power control of an inverter at each residence has been considered. In the previous research we demonstrated that about 20 percent of the output suppression loss was eliminated with reactive power control including PV voltage control when 225 residential PV were grid-interconnected. However, this was on a typical sunny spring day, the seasonal change of PV output and load power was not considered. So in this research we evaluated improved and smoothed generation efficiency among all residences with power factor and reactive power operating voltage through residential PV voltage control on clustered residential grid-interconnected PV for a period of one year. © 2012 IEEE.


Miyamoto Y.,Kandenko Co. | Hayashi Y.,Waseda University
IEEE PES Innovative Smart Grid Technologies Conference Europe, ISGT Europe | Year: 2010

Installing zero-emission power sources including photovoltaic power systems (PV) is necessary to cut greenhouse gas to reduce global warming. In Japan, the target capacity for installed PV in 2020 was set to 28 GW, which was 20 times the 2005 capacity. To achieve this target, PV should be installed in 70% of new houses. The PV output (active power) must be suppressed to sustain adequate voltage (within 101±6V), due to voltage increases by inverse power from PV when clustered residential PV systems are grid-interconnected on a distribution line, even if there is sufficient irradiance. Approaches to this problem should be considered both by power systems and distribution generation. We tried to start to optimize voltage control of clustered residential grid-interconnected PV to reduce loss due to voltage increase. In this research, we evaluated improved generation efficiency through residential PV voltage control on clustered residential grid-interconnected PV.


Miyamoto Y.,Kandenko Co. | Miyamoto Y.,Waseda University | Hayashi Y.,Waseda University
IEEJ Transactions on Power and Energy | Year: 2016

Recently home energy management system (HEMS) has been spread due to increase in awareness of save energy after Great East Japan Earthquake. HEMS consists of photovoltaic power system (PV), battery energy storage system (BESS) and heat pump water heater (HPWH), etc. Residential PV implementation rate has been increasing due to feed in tariff from 2009. So there is a danger of output suppression loss due to voltage increase on a distribution line due to reverse power flow from each residential PV. So we try to study how to reduce output suppression loss using BESS and HPWH optimally. One of the main purpose to implement BESS and HPWH is for economy using the difference in electricity charges between during nighttime and daytime. So in this research, we optimize how to operate BESS and HPWH to improve the benefit of the electric power selling charges and electricity charges considering reduction of output suppression loss and the difference in electricity charges between during nighttime and daytime. © 2016 The Institute of Electrical Engineers of Japan.


Miyamoto Y.,Kandenko Co. | Miyamoto Y.,Waseda University | Hayashi Y.,Waseda University
IEEJ Transactions on Power and Energy | Year: 2015

There is a danger of output suppression of high-penetration residential PV systems due to voltage increase. It is necessary to install new technology to prevent the occurrence of such phenomenon. Therefore, we focused our attention on heat pump water heaters (HPWHs). HPWHs are usually used to heat water during night time because electricity prices are cheaper than during the daytime for the load leveling in Japan. So they can be used as a countermeasure without additional cost if they are operated during the daytime. However, HPWHs do not have sufficient capacity to absorb inverse energy at each residence. Thus HPWH operation must be optimized to minimize output suppression loss. In this research, we selected four typical sunny days in spring, summer, autumn and winter. The optimal HPWH operation was calculated by numerical simulation. The optimal monthly HPWH operation was investigated using the weather forecast assuming actual operation in each season. © 2015 The Institute of Electrical Engineers of Japan.


Miyamoto Y.,Kandenko Co. | Hayashi Y.,Waseda University
17th Power Systems Computation Conference, PSCC 2011 | Year: 2011

In Japan, the target capacity for installed photovoltaic power systems (PV) in 2020 has been set to 28 GW. The PV output (active power) must be suppressed to sustain adequate voltage (within 101 ± 6V), which was established by the Electricity Business Act in Japan, due to voltage increases by inverse power from PV when clustered residential PV systems are grid-interconnected on a distribution line, even if sufficient irradiance exists. Simulation software was developed to analyze voltage increases when clustered PV were grid-interconnected on a large-scale demonstrative research in Ota City, Japan. From the previous fiscal year, the authors started to research improving whole generation efficiency at a site. We are developing to balance it among all the residences through voltage control, including power conditioning systems of a clustered residential grid-interconnected PV with the developed simulation software. For the subject, we have already demonstrated that 25 percent of the output suppression loss was eliminated with reactive power control when 225 residential PV are grid-interconnected to a simple single distribution line. In this research, a complex single distribution line, where 2160 residential PV are grid-interconnected, is set. We develop suitable voltage control for both simple and complex distribution lines.


Miyamoto Y.,Kandenko Co. | Hayashi Y.,Waseda University
Conference Record of the IEEE Photovoltaic Specialists Conference | Year: 2011

Installation zero-emission power sources, including photovoltaic power systems (PV), is necessary to cut greenhouse gasses to reduce global warming. In Japan, the target capacity for installed PV in 2020 has been set at 28 GW, which is 20 times the 2005 capacity. PV should be installed in 70 percent of new houses to reach this target. The PV output (active power) must be suppressed to sustain adequate voltage (within 101±6 V), due to voltage increases by inverse power from PV when clustered residential PV systems are grid-interconnected on a distribution line, even if there is sufficient irradiance. Simulation software was developed to analyze voltage increases when clustered PV were grid-interconnected on a large-scale demonstration research in Ota City in Japan. From the previous fiscal year, the authors started to research how to improve whole generation efficiency at a site and balance it among all the residences through voltage control including power conditioning systems of a clustered residential grid-interconnected PV with the developed simulation software. For the subject, we have already demonstrated that 25 percent of the output suppression loss was eliminated with reactive power control when 225 residential PV are grid-interconnected to a single distribution line. In this research, we have evaluated the influence of increasing and decreasing active and reactive power rate in residential PV voltage control on voltage deviation. © 2011 IEEE.


Tsuchida T.,Kandenko Co. | Tsuchida T.,Nagaoka University of Technology
IEEJ Transactions on Industry Applications | Year: 2012

An increasing number of voltage-driven-type PWM inverters have begun to be used recently for electrical equipment in buildings owing to energy conservation considerations. However, common-mode currents originate from this type of inverters, and problems due to such common-mode currents flowing in grounding systems of buildings have increased with their increased use. While it is necessary to study countermeasures to overcome these problems by considering the entire circuit in question (since common-mode currents flow in the whole circuit including power-supply and grounding systems), there seem to have been very few such studies. In this study, the author constructed a test circuit comprising a PWM inverter, an induction motor, and grounding electrodes, and he studied measures to suppress common-mode currents by using shielded cables and a grounding system. He also studied a method for grounding the shielding of the shielded cables used for the power supply from the inverter to the motor suppressing common-mode currents. © 2012 The Institute of Electrical Engineers of Japan.

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