Patents by Inventor Kazuyori Tahata
Kazuyori Tahata has filed for patents to protect the following inventions. This listing includes patent applications that are pending as well as patents that have already been granted by the United States Patent and Trademark Office (USPTO).
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Publication number: 20240146066Abstract: In a power grid stabilization system, a second energy storage system has a larger energy storage capacity than a first energy storage system. A bidirectional AC/DC converter is connected between an AC power grid and a pair of input and output terminals of the first energy storage system. A first bidirectional DC/DC converter is connected between the pair of input and output terminals of the first energy storage system and a pair of input and output terminals of the second energy storage system.Type: ApplicationFiled: June 1, 2021Publication date: May 2, 2024Applicant: Mitsubishi Electric CorporationInventors: Frederick PAGE, Yoshiyuki KONO, Kazuyori TAHATA, Shuhei FUJIWARA, Shinji TOMINAGA, Masatoshi TAKEDA
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Publication number: 20240088673Abstract: An electric power control system includes a plurality of power converters connected in parallel. Each power converter, among the plurality of power converters, converts a direct-current power of an electricity storage device connected to the power converter into an alternating-current power, and outputs the alternating-current power to the power system. The electric power control system further includes: a power generator simulation unit to simulate characteristics of the synchronous generator based on an aggregate active power to generate a phase of the alternating-current voltage; a signal generation unit to generate a control signal for the power converter, based on the phase of the alternating-current voltage. The power generator simulation unit generates a first angular frequency based on a first difference between the aggregate active power and a target value for the aggregate active power, and generates, based on the first angular frequency, the phase of the alternating-current voltage.Type: ApplicationFiled: February 5, 2021Publication date: March 14, 2024Applicant: Mitsubishi Electric CorporationInventors: Kazuyori TAHATA, Yoshiyuki KONO, Shuhei FUJIWARA, Shinji TOMINAGA
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Patent number: 11909307Abstract: A power conversion device includes a power converter including a plurality of arms and a control device to control voltages of a plurality of sub modules by PWM control using a carrier signal for each sub module. The sub module includes a plurality of switching elements, a power storage element, a pair of output terminals, and a bypass switch. When the control device detects failure of a sub module in an arm, it performs stop processing for stopping a switching operation of the plurality of switching elements included in at least one sub module of the plurality of sub modules in the arm and has the sub module failure of which was detected bypassed. After the control device performs the stop processing, it equalizes intervals among phases of carrier signals of a plurality of normal sub modules in the arm caused by failure of the sub module.Type: GrantFiled: June 12, 2019Date of Patent: February 20, 2024Assignee: MITSUBISHI ELECTRIC CORPORATIONInventors: Kazuyori Tahata, Shuhei Fujiwara, Takuya Kajiyama, Toshiyuki Fujii
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Publication number: 20240022183Abstract: A power conversion device includes a power converter including a plurality of arms each having a plurality of converter cells cascaded to each other. A control device includes an AC current controller to control AC current flowing between the power converter and an AC circuit and a circulating current controller to control circulating current flowing between the arms of the power converter. The AC current controller reduces an effective value or amplitude value of AC current in a discharge operation mode in which a voltage of a power storage element of each converter cell is discharged, compared with in a normal operation mode. The circulating current controller increases an effective value or amplitude value of circulating current in the discharge operation mode, compared with in the normal operation mode.Type: ApplicationFiled: December 9, 2020Publication date: January 18, 2024Applicant: Mitsubishi Electric CorporationInventors: Takuya KAJIYAMA, Toshiyuki FUJII, Shuhei FUJIWARA, Kazuyori TAHATA
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Publication number: 20240014669Abstract: A power storage apparatus of one embodiment includes a storage bank including a plurality of power storage elements connected to each other; and one or plurality of first cells. The storage bank and the one or plurality of first cells are connected in series to each other. Each first cell includes a pair of input/output nodes, a bridge circuit including at least two semiconductor switching elements, and a power storage element connected to the pair of input/output nodes via the bridge circuit. A storage capacity of the power storage element of each first cell is smaller than a storage capacity of the storage bank.Type: ApplicationFiled: November 11, 2020Publication date: January 11, 2024Applicant: Mitsubishi Electric CorporationInventors: Yoshiyuki KONO, Shuhei FUJIWARA, Kazuyori TAHATA, Frederick PAGE, Shinji TOMINAGA, Masatoshi TAKEDA
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Patent number: 11750080Abstract: A power converter includes an arm in which a plurality of converter cells are connected in series, each of the converter cells including at least two switching elements, a power storage element, and a pair of output terminals. A control device controls the power converter. The converter cell includes a switch to have the converter cell bypassed. When the control device senses failure of the converter cell, it has the failed converter cell within the arm bypassed and controls a normal converter cell within the arm to suppress a ratio of a harmonic component in an arm current that increases due to the failure.Type: GrantFiled: December 25, 2018Date of Patent: September 5, 2023Assignee: MITSUBISHI ELECTRIC CORPORATIONInventors: Takuya Kajiyama, Toshiyuki Fujii, Shuhei Fujiwara, Ryosuke Uda, Kazuyori Tahata
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Patent number: 11722069Abstract: A power conversion system includes: a self-excited power converter to perform power conversion between a first AC system and a DC system; a first transformer having a primary side connected to the first AC system and a secondary side connected to the self-excited power converter; and a first impedance circuit connected between a ground and a neutral point on the secondary side of the first transformer, or between the ground and an AC line connecting the secondary side of the first transformer and the self-excited power converter. The first impedance circuit includes one of a reactor and another transformer.Type: GrantFiled: August 8, 2019Date of Patent: August 8, 2023Assignee: MITSUBISHI ELECTRIC CORPORATIONInventors: Kazuyori Tahata, Fuminori Nakamura, Shigeo Hayashi
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Publication number: 20220311328Abstract: A power conversion device includes a power converter including a plurality of arms and a control device to control voltages of a plurality of sub modules by PWM control using a carrier signal for each sub module. The sub module includes a plurality of switching elements, a power storage element, a pair of output terminals, and a bypass switch. When the control device detects failure of a sub module in an arm, it performs stop processing for stopping a switching operation of the plurality of switching elements included in at least one sub module of the plurality of sub modules in the arm and has the sub module failure of which was detected bypassed. After the control device performs the stop processing, it equalizes intervals among phases of carrier signals of a plurality of normal sub modules in the arm caused by failure of the sub module.Type: ApplicationFiled: June 12, 2019Publication date: September 29, 2022Applicant: Mitsubishi Electric CorporationInventors: Kazuyori TAHATA, Shuhei FUJIWARA, Takuya KAJIYAMA, Toshiyuki FUJII
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Publication number: 20220263424Abstract: A power conversion system includes: a self-excited power converter to perform power conversion between a first AC system and a DC system; a first transformer having a primary side connected to the first AC system and a secondary side connected to the self-excited power converter; and a first impedance circuit connected between a ground and a neutral point on the secondary side of the first transformer, or between the ground and an AC line connecting the secondary side of the first transformer and the self-excited power converter. The first impedance circuit includes one of a reactor and another transformer.Type: ApplicationFiled: August 8, 2019Publication date: August 18, 2022Applicant: Mitsubishi Electric CorporationInventors: Kazuyori TAHATA, Fuminori NAKAMURA, Shigeo HAYASHI
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Patent number: 11336169Abstract: A power converter includes an arm in which a plurality of converter cells are connected in series, each of the converter cells including at least two switching elements, a power storage element and a pair of output terminals. A control device controls the power converter. The converter cell includes a switch to have the converter cell bypassed. When the control device senses failure of the converter cell, it has the failed converter cell bypassed, estimates an output voltage lost by bypassing the failed converter cell, and has a normal converter cell supply the estimated output voltage of the failed converter cell.Type: GrantFiled: December 25, 2018Date of Patent: May 17, 2022Assignee: Mitsubishi Electric CorporationInventors: Takuya Kajiyama, Toshiyuki Fujii, Shuhei Fujiwara, Ryosuke Uda, Kazuyori Tahata
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Patent number: 11283369Abstract: A control device for controlling a power source connected to an alternating-current (AC) power system includes: a frequency control unit that controls a frequency of the power source operating in a constant-voltage constant-frequency control scheme; a power calculation unit that calculates, when the frequency control unit varies a frequency of the power source, a variation of an effective power output from the power source; an arithmetic unit that calculates a frequency characteristics constant of the AC power system, based on a variation of the frequency of the power source and the variation of the effective power output from the power source; and a selection unit that selects a control scheme for the power source, based on the frequency characteristics constant of the AC power system.Type: GrantFiled: June 7, 2018Date of Patent: March 22, 2022Assignee: MITSUBISHI ELECTRIC CORPORATIONInventors: Shuhei Fujiwara, Yoshiyuki Kono, Kazuyori Tahata, Masashi Shigemitsu, Shota Midorikawa
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Publication number: 20220029524Abstract: A power converter includes an arm in which a plurality of converter cells are connected in series, each of the converter cells including at least two switching elements, a power storage element, and a pair of output terminals. A control device controls the power converter. The converter cell includes a switch to have the converter cell bypassed. When the control device senses failure of the converter cell, it has the failed converter cell within the arm bypassed and controls a normal converter cell within the arm to suppress a ratio of a harmonic component in an arm current that increases due to the failure.Type: ApplicationFiled: December 25, 2018Publication date: January 27, 2022Applicant: Mitsubishi Electric CorporationInventors: Takuya KAJIYAMA, Toshiyuki FUJII, Shuhei FUJIWARA, Ryosuke UDA, Kazuyori TAHATA
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Publication number: 20220014114Abstract: A power converter includes an arm in which a plurality of converter cells are connected in series, each of the converter cells including at least two switching elements, a power storage element, and a pair of output terminals. A control device controls voltages of the plurality of converter cells by phase shift PWM control using a carrier signal for each converter cell. The converter cell includes a switch to have the converter cell bypassed. When the control device senses failure of the converter cell within the arm, it has a failed converter cell within the arm bypassed and rectifies uneven intervals among phases of carrier signals of a plurality of normal converter cells within the arm caused by failure of the converter cell.Type: ApplicationFiled: December 25, 2018Publication date: January 13, 2022Applicant: Mitsubishi Electric CorporationInventors: Takuya KAJIYAMA, Toshiyuki FUJII, Shuhei FUJIWARA, Ryosuke UDA, Kazuyori TAHATA
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Publication number: 20210408895Abstract: A power converter includes an arm in which a plurality of converter cells are connected in series, each of the converter cells including at least two switching elements, a power storage element and a pair of output terminals. A control device controls the power converter. The converter cell includes a switch to have the converter cell bypassed. When the control device senses failure of the converter cell, it has the failed converter cell bypassed, estimates an output voltage lost by bypassing the failed converter cell, and has a normal converter cell supply the estimated output voltage of the failed converter cell.Type: ApplicationFiled: December 25, 2018Publication date: December 30, 2021Applicant: Mitsubishi Electric CorporationInventors: Takuya KAJIYAMA, Toshiyuki FUJII, Shuhei FUJIWARA, Ryosuke UDA, Kazuyori TAHATA
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Patent number: 11031882Abstract: A power conversion device includes power conversion circuitry including a plurality of submodules connected in series to each other. The power conversion device further includes: a signal reception unit configured to receive a signal representing a voltage of a capacitor in each of the submodules; a time calculation unit configured to calculate at least one of a charging time of the capacitor and a discharging time of the capacitor based on the signal; and a determination unit configured to determine whether the capacitor has degraded or not based on at least one of a first result of comparison of the charging time with a reference charging time serving as a reference for determining degradation of the capacitor, and a second result of comparison of the discharging time with a reference discharging time serving as a reference for determining degradation of the capacitor.Type: GrantFiled: May 26, 2017Date of Patent: June 8, 2021Assignee: MITSUBISHI ELECTRIC CORPORATIONInventors: Kazuyori Tahata, Yoshiyuki Kono, Kenichi Kuroda, Shuhei Fujiwara, Ryosuke Uda
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Publication number: 20210099102Abstract: A power conversion device includes power conversion circuitry including a plurality of submodules connected in series to each other. The power conversion device further includes: a signal reception unit configured to receive a signal representing a voltage of a capacitor in each of the submodules; a time calculation unit configured to calculate at least one of a charging time of the capacitor and a discharging time of the capacitor based on the signal; and a determination unit configured to determine whether the capacitor has degraded or not based on at least one of a first result of comparison of the charging time with a reference charging time serving as a reference for determining degradation of the capacitor, and a second result of comparison of the discharging time with a reference discharging time serving as a reference for determining degradation of the capacitor.Type: ApplicationFiled: May 26, 2017Publication date: April 1, 2021Applicant: Mitsubishi Electric CorporationInventors: Kazuyori TAHATA, Yoshiyuki KONO, Kenichi KURODA, Shuhei FUJIWARA, Ryosuke UDA
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Publication number: 20210021210Abstract: A control device for controlling a power source connected to an alternating-current (AC) power system includes: a frequency control unit that controls a frequency of the power source operating in a constant-voltage constant-frequency control scheme; a power calculation unit that calculates, when the frequency control unit varies a frequency of the power source, a variation of an effective power output from the power source; an arithmetic unit that calculates a frequency characteristics constant of the AC power system, based on a variation of the frequency of the power source and the variation of the effective power output from the power source; and a selection unit that selects a control scheme for the power source, based on the frequency characteristics constant of the AC power system.Type: ApplicationFiled: June 7, 2018Publication date: January 21, 2021Applicant: Mitsubishi Electric CorporationInventors: Shuhei FUJIWARA, Yoshiyuki KONO, Kazuyori TAHATA, Masashi SHIGEMITSU, Shota MIDORIKAWA
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Patent number: 10403449Abstract: A direct-current circuit includes: a breaker that is inserted into the direct-current line and becomes a path for direct current when in a steady state; a resonance circuit connected in parallel with the breaker and superimposing resonance current on the direct current; and a first disconnector and a second disconnector connected to first and second connection points of the breaker and the resonance circuit, respectively, and forming a path for the direct current together with the breaker. The resonance circuit includes a series circuit that includes a capacitor and a reactor and generates the resonance current, a charging resistor for charging the capacitor with a direct-current potential of the direct-current line, a high-speed switch connected in series with the series circuit on the capacitor side and superimposing the resonance current on the direct current, and an arrester connected in parallel with the capacitor and the high-speed switch.Type: GrantFiled: June 10, 2015Date of Patent: September 3, 2019Assignee: MITSUBISHI ELECTRIC CORPORATIONInventors: Shiken Ka, Hiroki Ito, Kunio Kikuchi, Makoto Miyashita, Kazuyori Tahata, Sho Tokoyoda, Kenji Kamei
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Publication number: 20190027327Abstract: A direct current circuit breaker used in a self-commutated direct current power transmission system includes a high-speed circuit breaker and a low-speed circuit breaker connected in series. The high-speed circuit breaker includes a high-speed circuit breaker interruption unit to interrupt a DC current flowing through a direct current line when a fault has occurred, and a current limiting element connected in parallel therewith. The low-speed circuit breaker includes a low-speed circuit breaker interruption unit to interrupt a DC current when a fault has occurred. A time required for the high-speed circuit breaker interruption unit to interrupt the DC current is shorter than a time required for the low-speed circuit breaker interruption unit. The low-speed circuit breaker interruption unit completes interruption of the DC current before a voltage applied to the current limiting element becomes lower than a minimum voltage allowable for the system.Type: ApplicationFiled: February 5, 2016Publication date: January 24, 2019Applicant: MITSUBISHI ELECTRIC CORPORATIONInventors: Kazuyori TAHATA, Kunio KIKUCHI, Makoto MIYASHITA, Kenji KAMEI, Sho TOKOYODA
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Patent number: 10184452Abstract: A wind power generation system according to the present invention includes: a DC bus; a plurality of feeders connected to the DC bus for transmitting DC powers to the DC bus; a plurality of wind power generators; a plurality of AC/DC converters connected one by one to each of the wind power generators for converting AC powers generated by the connected wind power generators, into DC powers, and outputting the DC powers to the feeders; and a DC breaker and a diode, which serve as a current limiting unit installed on each of the feeders for preventing a DC current from flowing from the DC bus into the feeder.Type: GrantFiled: September 16, 2014Date of Patent: January 22, 2019Assignee: MITSUBISHI ELECTRIC CORPORATIONInventors: Kazuyori Tahata, Kunio Kikuchi, Makoto Miyashita, Kenji Kamei, Sho Tokoyoda