IEEJ Journal of Industry Applications
Vol.8 No.3 pp.421–429
DOI: 10.1541/ieejjia.8.421

Paper

Control of Starter Generator in a UAV with a Micro Jet Engine
Jun-ichi Itoh∗a)
Keisuke Kusaka∗
Hiroyuki Koshikizawa∗∗∗

Senior Member,
Member,Non-member,

Kazuki Kawamura∗
Yoshiya Ohnuma∗∗Kazuyuki Abe∗∗∗MemberMemberNon-member(Manuscript received June 25, 2018)

A control method of a starter generator, which are for a jet engine for an unmanned aerial vehicle (UAV) system is
proposed in this paper. Both the jet engine and the propellers that are powered by the jet engine via a starter generator
generates the thrust power. Using the jet engine for obtaining the thrust, it is possible to extend a flight range since
the energy density of the jet engine of the developed system is higher than the energy density of the battery in theconventional system. The miniaturization is also achieved by connecting the starter generator to the jet engine because
high-frequency operation makes the starter generator compact. The proposed control strategy achieves the starting,powering, and cooling operations using the starter generator. Each operation is demonstrated with a 3-kW prototype.
As the results, the maximum conversion eﬃciency of 92.7% is observed. Moreover, the minimum total harmonic
distortion of the generator current is 16.5% at the rated operation speed (70000 r/min). Further, the exhaust nozzle
temperature is stabilized within the maximum deviation of 2% of the command in a steady state.
Keywords: starter generator, jet engine, unmanned aerial vehicle (UAV), V/f control

1.

is low. Due to the low speed, a volume of the generator tends
to be large in a high-power UAV system.
A UAV system with a jet engine and its control strategy ofthe starter generator are proposed in this paper. In the system, only the starter generator have the role of starting andcooling operation without an APU. Furthermore, the starter
generator is directly connected to the jet engine without a reduction gear and rotated at high speed for miniaturization.
The challenge in the study is achieving the stable operationand mode shift among the operation modes; starting mode,
powering mode, and cooling mode, by the proposed control
scheme. In particular, the synchronous frequency command
limiter and output power limiter is implemented for the stable operation in the proposed control method. Additionally,
new modulation method using a modified carrier via the estimated intersection phase based on synchronous PWM is experimentally demonstrated. The experimental results showthat the prototype achieves a maximum conversion eﬃciencyof 92.7%, and the minimum THD of the generator current
is 16.5% at a rotation speed of 70000 r/min. Additionally,a temperature of an exhaust nozzle is controlled within the
maximum deviation of 2% in comparison with the command
temperature in the steady state.

Introduction

In recent years, UAVs have been actively studied for
rescue activities in natural disasters (1)–(4) . Specifically, themulticopter-type UAV has two features: the multicopter UAV
does not require a designated landing space, the unmanned
operation makes it possible to approach danger zones. In
UAVs, which had been previously developed, the multicopter
UAV is generally powered by batteries (2) . Due to the limitation of the battery energy density (5) , a loading weight and aflight range are limited. In order to overcome this disadvantage, a UAV with a jet engine has been developed (6) . Thrustis generated via both the jet engine and propellers that are
powered by the jet engine through the starter generator in thedeveloped UAV system. Using the jet engine as a thrust generator, the flight range can be extended because the energy
density of the jet engine and fuel is greater than the energy
density of the battery. Furthermore, the jet engine with remaining fuel can be used as an emergency power supply using the starter generator after the flight.
An auxiliary power unit (APU) is generally used for starting and cooling the jet engine (7) (8) . The use of APU has the
problem, which causes the increases in the cost and size ofthe system because the rotation speed of the generator, whichis connected via reduction gears (9) (10) to the jet engine, in APU

2.

Figure 1 shows the configuration of the UAV system,
which is developed in this paper. The feature of this system is that it has no reduction gears between the jet engine
and the starter generator. The jet engine supplies power tosix propellers through the starter generator. For the aerial applications, weight reduction of the starter generator is important issue from the view of extending a flight range. Thus, thehigh rotation speed is required for miniaturization and weighta) Correspondence to: Jun-ichi Itoh. E-mail: itoh@vos.nagaoka
ut.ac.jp∗
Nagaoka University of Technology
1603-1, Kamitomioka, Nagaoka, Niigata 940-2188, Japan∗∗
Nagaoka Power Electronics Co., Ltd.
2085-16, Fukasawa, Nagaoka, Niigata 940-2135, Japan∗∗∗YSEC Co., Ltd.
8460-1, Urushiyama, Nishi-kanku, Niigata 953-0054, Japanc 2019 The Institute of Electrical Engineers of Japan.


System Configuration of UAV System

421

Generator Control in UAV with a Jet Engine（Jun-ichi Itoh et al.）The system is operated with the powering operation within
the rotation speed range from 50000 to 70000 r/min, and thebattery is charged. The jet engine controls the speed while
the starter generator controls the output power.
E. Stop Mode
The engine output is halted then the starter generator decelerates and cools the jet engine. The operation of the power
converter continues till the temperature of the exhaust nozzleof the jet engine cool down to 50◦ C or lower. Subsequently,
the operation mode is shifted to the all-oﬀ mode.

Fig. 1. System configuration of the developed UAV system

3.

Modulation for Suppressing Even-order Harmonic Components

3.1 Continuous PWM
The generator current composes the low-order harmonic components and beat components because the carrier frequency and the fundamental frequency are closed owing to the direct connection of the generator and the jet engine. For the high-frequency operation,
the nine-pulse synchronous PWM technique is implemented
during the Run Mode.
Figure 3 shows the voltage command of the continuous
PWM. In this figure, the waveforms with a modulation index of 0.8 and a triangular carrier with a frequency ratio ofnine are illustrated. As shown in Fig. 3(a), PWM signal isgenerally generated by comparing the voltage command vu ∗and the triangular carrier. Figure 3(b) shows the modulationindex command V m ∗ and modified carrier umc . The modified
carrier is used for the carrier comparison. The modified carrier umc is expressed by(a) Flowchart of the mode change of the proposed UAV system.

umc =

um
sin θ

(θ  0 deg, 180 deg)· · · · · · · · · · · · · · · (1)where θ denotes the phase of voltage command and um denotes the triangular carrier.
The intersection phase of the modulation signal and thecarrier is estimated by using a look-up table of the modified carriers in a DSP in the proposed modulation method.
Then a voltage command based on the estimated intersection
phase is output. The proposed control can be implemented toa micro-controller because the proposed modulation method
does not need a change of the hardware.
Table 1 shows the estimated intersection phase patterns of
the continuous PWM. Due to the synchronous PWM, the estimated intersection phases of sectors zero and nine are determined as 0◦ and 180◦ , respectively as shown in Table 1. The
relationship between the phase and modulation index command of the modified carrier umc of sectors 1, 2, 3, and 4 is(b) Mode transition of the jet generator.

Fig. 2. Diagram of the mode transition for the developed
UAV system

reduction.
Figure 2 is the diagram of the mode transition of the UAV
system. An operation mode is selected by a host controller.
There are five operation modes as shown below.
A. All oﬀ Mode
The mode is a stationary state. The power converters are
not activated. It means that all of the switches are oﬀ.
B. Standby Mode
The DC-DC converter is activated. The DC-DC converter
boosts the DC-link voltage from the battery voltage to 300 V.
In this mode, the AC/DC converter is not activated.
C. Startup Mode
The AC/DC converter is activated. The starter generator
assist in both the ignition of the jet engine and acceleration up
to 50000 r/min. The host controller controls the starter generator speed in the aforementioned state. The temperature of
the exhaust nozzle of the jet engine is also controlled.
D. Run Mode

Fig. 3. Waveforms of the voltage commands and carriers
with the continuous PWM
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Generator Control in UAV with a Jet Engine（Jun-ichi Itoh et al.）Table 1. Estimation of phase patterns with the continuous
PWM

Table 2. Estimation of phase patterns with the discontinuous PWM

It should be noted that in the section exceeding 60 deg. insector three, the intersection phase is set to 60 deg. when themodulation index is 0.577 or lower.
Table 2 lists the estimated intersection phase patterns of
the discontinuous PWM. The relationship between the phaseand modulation index command of the deformed carrier umd
of sectors one, two, and three is defined as given in look-up
Tables 1, 2, and 3. By referring the phases α1 , α2 , and α3 via
the modulation index from the look-up tables, the intersection
phase of the carrier and modulation signal in each sector isestimated by the relationship shown in Table 2. By using themethod, the symmetry of the PWM signal is ensured even in
the discontinuous modulation, and the even-order harmoniccomponents is not appear on the generator current.

Fig. 4. Waveforms of the voltage commands and carriers
with the discontinuous PWM

shown in Tables 1, 2, 3, and 4. It should be noted that α1 , α2 ,α3 , and α4 correspond to the estimated intersection phases
referred to the look-up tables. With respect to sector five andabove, it is not necessary to prepare the tables to estimate
the phase by using the symmetry at every 90 deg. The proposed modulation method obtains the estimated intersection
phase in each sector using the phase according to look-up tables 1 to 4 and the relationship in Table 1 and outputs a voltage command based on the estimated intersection phase. The
generated PWM signal is equivalent to that generated via theanalog control. Therefore, even-order harmonic components
are not composed on the generator current.
3.2 Discontinuous PWM
Figure 4 shows the carriercomparison of discontinuous PWM when a frequency ratioof the carrier signal to the modulation signal is nine. The
waveforms with a modulation index of 0.8 is illustrated inthig figure. The discontinuous PWM signal v xd ∗ shown in
Fig. 4(a) is calculated by adding the following oﬀset to thethree-phase modulation signal v x :4.

Control Scheme for Starter Generator

Figure 5 shows the configuration of the power converters.
The system has an interleaved DC-DC converter with fourlegs and a three-phase inverter. The DC-DC converter is usedbecause the battery voltage is approximately 50 V. The DC
voltage must be boosted to 300 V for the drive of the inverter.
Figure 6 shows the control block diagram of the DCDC converter. The DC-DC converter regulates the DC
link voltage V dc to the voltage command. The current is
independently controlled in each leg to suppress the currentv∗xd = v∗x + v∗oﬀset , (x = u, v, w)

1 − |vmax | if |vmax | ≥ |vmin |,∗voﬀset =· · · · · · · · · (2)−1 + |vmin | if |vmin | < |vmax |,v= max[v∗u , v∗v , v∗w ]and max
vmin = min[v∗u , v∗v , v∗w ]Fig. 5. System configuration of the starter generator andinterleaved DC-DC converter

A modified carrier umd shown in Fig. 4(b) is used as mentioned in Section A. The intersection phases in sectors zeroand four are defined as 0 deg. and 90 deg., respectively, inadvance. Therefore, the modified carriers of sectors one,
two, and three are only required to estimate the intersection
phases. The modified carrier umd is calculated by (2) in the
discontinuous PWM.
um + 1(10◦ ≤ θ < 60◦ )· · · · (3)umd =sin θ − sin(θ − 120◦ )Fig. 6. Block diagram of the interleaved DC-DC converter
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Generator Control in UAV with a Jet Engine（Jun-ichi Itoh et al.）Fig. 7. Control block diagram of the 3-phase inverter

imbalance among four legs. The carrier for two legs is phaseshifted by half the switching period. Thus, the current ripple
is reduced to half (11) of the non-interleaved DC/DC converter
because the switching frequency is equivalently doubled.
Figure 7 shows the control block diagram of the AC-DC
converter. The V/f control is employed except the run mode.
In the run mode, a power control is necessary for stable operation of the jet engine.
The rotation speed of the jet engine may suddenly decreaseat the mode change from the V/f control to the output power
control or exhaust nozzle temperature control when the output power of the jet engine is not suﬃciently high. Hence,the stable operation of the jet engine at a low speed is diﬃcult. In order to overcome the problem, a synchronous frequency command limiter is applied. By the frequency command limit, the speed is maintained at constant until the jetengine output becomes suﬃciently high. Besides, the generator torque may suddenly changes during the startup mode. In
order to prevent the converter from the overcurrent during theoperation, an output power limiter is implemented. The synchronous frequency command is compensated to avoid thesudden change in the torque. Around the rated speed, discontinuous PWM is employed to achieve the operation in an
over-modulation region.
5.

Fig. 8. Relation between the rotation speed and thrust of
the jet engine

Fig. 9. Control block diagram of the output power withthe jet engine

the response of the rotation speed control for the jet engine issuﬃciently slower than the response of the output power control. Assuming that the loss can be ignored, the total powerof the jet engine P jet is calculated as follows:

Stabilization Analysis of the Power Generation
Output Control

P jet = Pth + Pout · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · (5)Figure 8 shows the relation between the rotation speed andthe thrust of the jet engine. A thrust of 68.0 N is obtainedat the rotation speed of 70000 r/min. Assuming that the atmospheric temperature and air density are constant under theatmospheric pressure, the thrust of the jet engine depends on
only the rotational speed irrespective of the output power.
The thrust of the jet engine is proportional to the cube of
the rotational speed, and thus, the thrust F obtained by themeasured value is approximated by the cube of the rotational
speed as follows:

where Pth is the thrust power of the jet engine. The thrust
power is added to the shaft power Pout that drives the propeller. The shaft power is determined by the flight speed andthrust of the aircraft. However, if the aircraft is stationary
as in the test, the shaft power cannot be calculated from theflight speed. In this case, the stationary shaft power Pth s is
calculated as follows:
F× 736· · · · · · · · · · · · · · · · · · · · · · · · · · · · · · (6)Pth s =
11.2
Substituting (4) into (6), the stationary shaft power (12) iscalculated as follows
736kF 3Pth s =
ω = kth ω3 · · · · · · · · · · · · · · · · · · · · · · · · (7)11.2
with the coeﬃcient kth :The rotation angular velocity is linearized to analyze thestability of the control around the steady state by (8).

F = kF ω3 · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · (4)where k F denotes the coeﬃcient obtained from the experiment, and ω denotes the rotation speed of the jet engine.
Figure 9 shows the block diagram of the output power control system with the jet engine. In the proposed system, synchronous angular frequency ωg of the generator is generated
via the diﬀerence between the output power command Pout ∗and detected output power Pout . In addition, it is assumed thatPth s = 3kth ω0 2 ω· · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · (8)424

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Generator Control in UAV with a Jet Engine（Jun-ichi Itoh et al.）Fig. 10. Roots locus with changing the initial angularvelocity ω0

Fig. 11. Step response of output power with the changeof output power command from 0.3 p.u. to 0.5 p.u

It should be noted that ωo denotes the initial angular velocity at the steady-state point. Thus, the transfer function from
input to output of the control system is expressed as follows:

and this corresponds to the low-speed range. However, thistype of large overshoot does not occur because the power
generation operation is only performed in the high-speed
range in the system.

9K p kvf 2 kth ω0 2
Ki r 2 J
G(s) =
2
2
9K p kvf 2 kth ω0 2
9K
k
k
ω
p
vf
th
0 s
−
s2 −
r2 J
Ki r 2 J· · · · · · · · · · · · · · · · · · · · (9)−6.

Experimental Results

6.1 Modulation Method for Even-order Harmonic
Component Suppression
Figure 12 shows the experimental system. Table 3 shows the specification of the starter
generator. In this test, the induction motor is mechanicallyconnected to the generator to emulate the jet engine. Additionally, a small-capacity DC power supply is connected to
the DC-ling via the diode. The DC power supply is used tosupply the excitation current at the time of starting instead of
the battery because the starter generator is an induction generator.
Figure 13 shows a block diagram of the three-phase PWM
converter. The control system adjusts the slip angle frequency and controls the DC-link voltage. In the high-speed
range, the modulation scheme is shifted from the asynchronous PWM to the synchronous PWM. The discontinuous
PWM is selected around the rated speed to keep the operationeven in the over-modulation region.

where r2 denotes the secondary winding resistance of thegenerator, J is the total inertia of the jet engine and generator, kvf is the voltage coeﬃcient in the v/f control, K p is the
proportional control gain, and K i is the integral control gain.
Furthermore, the gain K i and K p are expressed as functionsof the response angular frequency ωn and damping coeﬃcientζ.
2ξωn r2 J· · · · · · · · · · · · · · · · · · · · · · · · · · · (10)9kvf 2 kth ω0  2
2ξ
· · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · (11)Ki =ωnKp = −It should be noted that ω0 is the initial speed. The angularspeed should be set accordingly to the detection value of theangular speed. However, the angular velocity detection is not
employed in the test, and thus, the value is predetermined asfollows.
Figure 10 shows the roots locus with changing the initial
angular velocity ω0 . In the system, the powering operationis performed in the rotation speed range from 0.7 to 1.0 p.u.
Therefore, the initial angular velocity setting value ω0 ’ is
0.7 p.u. The damping coeﬃcient ζ is designed to be 0.7. The
response angular frequency ωn is designed for making overshoot time 0.05 s; this is 1/10 of the control period of the jetengine. As shown in Fig. 10, the control system is on the instability threshold when the rotation speed is 0 p.u. because
the poles are located on the imaginary axis. The control system is always stable because the poles move to the negative
half plane when the rotation speed exceeds 0 p.u.
Figure 11 shows the step response of output power when
the output power command changes from 0.3 p.u. to 0.5 p.u.
As shown in Fig. 11, the response equals or exceeds the design response time at rotation speeds of 0.7 p.u. and 1.0 p.u.
The response time is delayed, and a large overshoot occurs
in output power at the rotation speeds of 0.4 p.u. and 0.1 p.u.,

Fig. 12. Experimental setup
Table 3. Specifications of the starter generator

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Generator Control in UAV with a Jet Engine（Jun-ichi Itoh et al.）Fig. 13. Control block diagram of the three-phase PWM
converter(a) Conventional method.

(b) Proposed method.

Fig. 16. Operation waveforms of PWM converter withthe discontinuous PWM(a) Conventional method.

(b) Proposed method.

Fig. 14. Operation waveforms of PWM converter withthe continuous PWM(a) Conventional method.

(b) Proposed method.

Fig. 17. Harmonics analysis of the generator current
with the discontinuous PWM(a) Conventional method.

is reduced by 99.2% in comparison with the conventional
method. Besides, total harmonic distortion (THD) of the generator current is reduced by 9.99% compared to that in theconventional method.
Figure 16 shows the operation waveforms of the discontinuous PWM at a rotation speed of 1.0 p.u. The frequency
ratio of the carrier frequency to the output frequency is nine.
The modulation index is 1.08, and the conventional method
and proposed method control the output voltage at a constantvalue at 300 V.
Figure 17 shows the result of a harmonic analysis of thegenerator current with the discontinuous PWM. As shown in
Fig. 17(b), the proposed method is eﬀective to suppress low
even-order harmonic components, such as the second, eighth,and tenth order components, which are generated by the conventional method. Additionally, the eighth harmonic component is reduced by 99.1% in comparison with that in theconventional method. Beside, THD of the generator current
is reduced by 7.14% compared to that in the conventional
method.
From the above experiments, the eﬀectiveness of the proposed modulation methods in both the discontinuous PWM
and the continuous PWM are verified.
6.2 Control Strategy for Starter Generator
Table 4(b) Proposed method.

Fig. 15. Harmonics analysis of the generator current
with the continuous PWM

Figure 14 shows the operation waveforms of the AC/DC
converter with continuous PWM. The frequency ratio of thecarrier frequency and the output frequency is nine and therotation speed of 0.8 p.u. The waveforms are the input voltage of AC-DC converter, generator current, and output DC
voltage. The modulation index is 0.871, and the conventional
and proposed methods control the output voltage at constant(300 V).
Figure 15 shows the harmonic analysis of the generator
current of the continuous PWM. As shown in Fig. 15(b),the proposed method is eﬀective to suppress low evenorder harmonic components, such as the second, eighth, andtenth order components, which are generated by the conventional method. In addition, the eighth harmonic component
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Generator Control in UAV with a Jet Engine（Jun-ichi Itoh et al.）Table 4. Specification of the jet engine

Fig. 21. THD characteristics of the generator current

Fig. 18. Developed jet engine and generator

Fig. 22. Eﬃciency characteristics of the power converter

Fig. 19. Operation waveforms when the generator is operated in the Run Mode
Fig. 23. Characteristics of the exhaust nozzle temperature relative to rotation speed and output power and output power command based on rotation speed

even-order low harmonic components are less than 0.2%, andthis is suﬃciently smaller than the fundamental component.
Figure 21 shows the characteristics of the generator current THD relative to output power. As shown in Fig. 21, a
minimum current THD of 16.5% is achieved with an output
power of 2.98 kW at the rotation speed of 70000 r/min. Thisis because the fundamental component of the generator current increases when the output power increases.
Figure 22 shows the eﬃciency characteristics of the proposed system. Figure 22 shows that a maximum eﬃciencyof 92.7% is achieved with an output power of 2.98 kW at a
rotation speed of 70000 r/min.
Figure 23 shows the temperature characteristics of the exhaust nozzle relative to rotation speed, and the output power
when the ambient temperature is 26◦ C. The output power increases with increasing in the rotation speed of the jet engine at the same exhaust nozzle temperature. Additionally,
the system exhibits highest eﬃciency when the exhaust nozzle temperature is approximately 800◦ C. Therefore, an output power command depending to the rotation speed should

Fig. 20. Harmonic components on the generator current
during the Run mode shown in Fig. 19

and Figure 18 and shows the specifications of the jet engine and the prototype of the jet generator, respectively. The
starter generator and the jet engine are mechanically connected without a reduction gear.
Figure 19 shows the experimental waveforms of the ACDC converter during the Run Mode. The rotation speed isa rated speed of 70000 r/min. The output power is 2.98 kW.
The DC link voltage is regulated at 300 V. Moreover, a stable
power generation operation is achieved because the battery
current is constant at any rotation speed.
Figure 20 shows the harmonic components on the generator current, which is shown in Fig. 19. As shown in Fig. 20,
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Generator Control in UAV with a Jet Engine（Jun-ichi Itoh et al.）without decelerating and overcurrent among the operation
modes is achieved using the synchronous frequency command limiter and the output power limiter. Additionally, thesuppression method of the low even-order harmonic components, which is caused when the output frequency and thecarrier frequency is closed, are demonstrated. The proposed
modulation method uses the estimated intersection phase forthe synchronous PWM. The 3-kW prototype system achieves
minimum generator current THD of 16.5% at a rated rotational speed of 70000 r/min. At the rotational speed, a maximum conversion eﬃciency of the prototype is 92.7%. Additionally, the exhaust nozzle temperature is controlled within
the maximum deviation corresponding to 2% of the command value.
Acknowledgment
The paper is organized based on the results obtained from a
project subsidized by New Energy and Industrial Technology
Development Organization (NEDO) of Japan.

References(1)Fig. 24. Experimental results of operation of jet generator
(2)

(3)

be determined on the dotted line in Fig. 23.
Figure 24 shows the experimental results of the jetgenerator operation with the exhaust nozzle temperature control. The exhaust nozzle temperature command is 800◦ C. The
jet engine is accelerated to 60000 r/min, 65000 r/min, and70000 r/min in the run mode. Subsequently, the jet engine isdecelerated to 60000 r/min. As shown in Fig. 24, even when
the rotation speed accelerates or decelerates, the exhaust nozzle temperature converges to the command value. The exhaust nozzle temperature can be controlled within the maximum deviation of 2% of the command value in the steadystate. Around the 300 s, the exhaust nozzle temperature at
70000 r/min decreases from 800◦ C to 700◦ C because the inflow current of the battery is limited for the protection. From
this result, the proposed control method achieves the starting, powering, and cooling operations. Transition without
the deceleration is achieved via the synchronous frequency
command limiter when the startup mode changes to the runmode.
The output power gradually approaches zero after the transition because the starter generator maintains the rotation
speed until the output power of the jet engine becomes suﬃciently high. The acceleration without overload is achieved in
the startup mode via an output power limiter, and this limits
a command to 1 kW. Furthermore, the starter generator decelerates by a free run when the operation mode transitions
to the stop mode from the run mode. Subsequently, the inverter restarts at a rotation speed of 1000 r/min. The starter
generator simultaneously performs the cooling operation.
7.

(4)

(5)
(6)
(7)

(8)

(9)

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Conclusion

In the study, the control method of the starter generator fora UAV with a jet engine has been proposed. Stable transition
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Generator Control in UAV with a Jet Engine（Jun-ichi Itoh et al.）Jun-ichi Itoh (Senior Member) was born in Tokyo, Japan, in 1972. Hereceived his M.S. and Ph.D. degree in electrical andelectronic systems engineering from Nagaoka University of Technology, Niigata, Japan in 1996, 2000,
respectively. From 1996 to 2004, he was with Fuji
Electric Corporate Research and Development Ltd.,Tokyo, Japan. He was with Nagaoka University ofTechnology, Niigata, Japan as an associate professor.
Since 2017, he has been a professor. His research interests are matrix converters, dc-dc converters, power
factor correction techniques, energy storage system and adjustable speed
drive systems. He received IEEJ Academic Promotion Award (IEEJ Technical Development Award) in 2007. In addition, he also received Isao Takahashi Power Electronics Award in IPEC-Sapporo 2010 from IEEJ, 58th
OHM Technology Award from The Foundation for Electrical Science andEngineering, November, 2011, Intelligent Cosmos Award from Intelligent
Cosmos Foundation for the Promotion of Science, May, 2012, and Third
prize award from Energy Conversion Congress and Exposition-Asia, June,
2013. Prizes for Science and Technology (Development Category) from theCommendation for Science and Technology by the Minister of Education,
Culture, Sports, Science and Technology, April 2017. Dr. Itoh is a senior
member of the Institute of Electrical Engineers of Japan, the Society of Automotive Engineers of Japan and the IEEE.

Yoshiya Ohnuma (Member) received his M.S. and Ph.D. degrees
in electrical, electronics and information engineering from Nagaoka University of Technology, Niigata,Japan in 2010 and 2013, respectively. Since 2013,
he has been working at Nagaoka Power Electronics
Co., Ltd. His research interests include power conversion system especially matrix converters, DC-DC
converters and high-frequency techniques for power
converters. He is a member of IEEE and IEEJ.

Hiroyuki Koshikizawa (Non-member) was born in Japan, in 1987.
He received his B.S. degree in mechanical and control engineering from Niigata Institute of Technology,
Niigata, Japan in 2008. Since 2010, he has been withYSEC Co., LTD. He has been worked on designingand developing a micro jet engine for UAV, medical
equipment, and a food factory line.

Kazuyuki Abe (Non-member) was born in Japan, in 1971. He graduated Niigata prefectural maki high school in 1989.
From 1989 to 2009, He was with KEISEI MEDICALINDUSTRIAL Co., LTD. Since 2009, he has beenwith YSEC Co., LTD. He has been worked on designing and developing a micro jet engine for UAV,and medical equipment.

Kazuki Kawamura (Member) was born in Japan, in 1993. He received his B.S. degree from National Institute ofTechnology, Niihama College, Japan in 2016. In
2018, he received his M.S. degree in electrical, electronics and information engineering from Nagaoka
University of Technology, Niigata, Japan in 2018.
Since 2018, he has been with Daikin Industries Ltd.,
Japan.

Keisuke Kusaka (Member) received his B.S. and M.S. degrees from
Nagaoka University of Technology, Niigata, Japan in
2011, 2013, respectively. From 2015 to 2016, he waswith Swiss Federal Institute of Technology in Lausanne (EPFL), Switzerland as a trainee. In 2016,
he received his Ph.D. degree in energy and environment science from Nagaoka University of Technology. From 2016 to 2018, he was with Nagaoka University of Technology as a researcher. He is currently
an assistant professor at Nagaoka University of Technology. His current research interests include an inductive power transfer
system and high-frequency converters. He received the second prize paper
award in IPEC-Niigata 2018.

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IEEJ Journal IA, Vol.8, No.3, 2019