電気学会論文誌●（●●●●●●●部門誌）
IEEJ Transactions on ●●●●●●●●●●●●●●●
Vol.●● No.● pp.●-●
DOI: ●.●●/ieejeiss.●●.●

Paper
Efficiency Evaluation of a Matrix Converterwith a Boost-Up AC Chopper in an Adjustable Drive System
Kazuhiro Koiwa＊a), Student Member,

Jun-ichi Itoh＊, Member(Manuscript received Jan. 00, 20XX, revised May 00, 20XX)
This paper proposes a circuit topology for a matrix converter with a boost-up AC chopper in the input stage in order to improvethe voltage transfer ratio, which is defined as the ratio between the input and output voltages. The proposed system is applied in
an IPMSM adjustable speed drive system where the application range of flux-weakening control is wide. In order to drive themotor at the rated speed in the high-torque region, there are three possible solutions: (i) applying flux-weakening control, (ii)boosting up the voltage by the AC chopper or (iii) a combination of both the solutions (i) and (ii). In terms of the total loss, theproposed system with the solutions (ii) or (iii) is compared with the conventional matrix converter by using solution (i).
Consequently, the chopper loss in the AC chopper and the copper loss of the motor are calculated theoretically to evaluate thetotal loss. In addition, the proposed system is demonstrated as a 3.7-kW prototype by experiments. In this paper, the input voltage
is degraded so that a larger boost-up ratio can be applied to the AC chopper. Further, the proposed system is compared to theconventional matrix converter by expanding the range of flux-weakening control, which depends on the input voltage. As a result,
it is confirmed that the converter efficiency of the proposed system reaches 94.8% at the maximum point. Furthermore, it isrevealed that the efficiency of the proposed system is higher when the rated motor voltage is greater than 107% of the input
voltage.
Keywords : matrix converter, V-connection AC chopper, flux-weakening control, IPMSM

reduced because the output current is increased. In other words,
the motor loss in an adjustable speed drive system inherently
increases owing to the implementation of flux-weakening control.
One of the solutions is to redesign the motor in order to reduce therated voltage for application in a conventional MC. However, thedevelopment cost increases, and the size of the winding is larger
owing to the larger amount of motor current. In addition, therestricted voltage transfer ratio also limits the applicability of theMCs. Therefore, boost-up functionality is important in order toextend the application of the MC.
In order to solve this problem, a matrix-reactance frequency
converter (MRFC), which consists of an MC and an AC chopper,
has been studied(7)(8). References [7] and [8] showed that theamplitude of the output voltage is controlled such that it is higher
than the input voltage. However, the MRFC requires many
components including a boost-up reactor and capacitor. In addition,
the control of the MRFC becomes complicated because regularsynchronization is required between the MC and the chopper.
On the other hand, another MC, which can only boost-up thevoltage, is connected in the previous stage of the MC(1). In otherwords, this circuit comprises a back-to-back configuration near thefilter capacitor. When the MC operates in the boost-up mode, highefficiency is obtained. However, the number of switching devices
is twice that of the conventional MC; thus, the cost increases.
The authors previously proposed a circuit topology thatconnects a V-connection AC chopper in the input stage of the MC,
which enables boost-up functionality in order to overcome theproblems incurred in the past works. The proposed system isapplied to an adjustable speed drive system where the application
range of flux-weakening control is wide. In the proposed system,
flux-weakening control is applied at the same rotating speed of the

1. Introduction
A matrix converter (MC), which directly converts an AC power
supply voltage into an AC output voltage of variable amplitudeand frequency without large energy storage devices such as
electrolytic capacitors have been actively studied recently(1)-(3).
The following advantages are realized as compared with aback-to-back (BTB) converter, which consists of a PWM rectifier
and a PWM inverter: (i) reduced size, low-weight, and long
lifetime owing to the absence of a large electrolytic capacitor in
the main circuit; (ii) high efficiency because of a lower number ofswitching devices in the turn-on current path; and (iii) use of MC
avoids the increase in temperature of the switching devices in
low-output-frequency operation. Future applications of the MC in
the renewable energy field, such as in hybrid electric vehicle
systems and wind power generator systems, are expected. In orderto render hybrid electric vehicle systems and home appliances
more efficient, a high terminal voltage of the motor is required.
However, one of the disadvantages of the MC is that the voltage
transfer ratio, which is defined as the ratio between the output
voltage and the input voltage, is reduced to 0.866(2). Consequently,
the amount of output current of the MC is greater than that of the
BTB system for the same output power. When the rated voltage ofthe motor applied in a conventional MC is similar to that of the
BTB system, flux-weakening control is applied at a lower rotating
speed when compared with that of the BTB system(3)-(6). However,there is a possibility that the total efficiency of the system isa) Correspondence to: Kazuhiro Koiwa. E-mail:newkoiwa@stn.nagaokaut.ac.jp＊
Nagaoka University of Technology
1603-1, Kamitomioka-machi, Nagaoka city, Niigata, Japan 940-2188© 200● The Institute of Electrical Engineers of Japan.

1Evaluation of Boost-up Matrix Converter in Drive system(Kazuhiro Koiwa et al.)

BTB system because the already insufficient output voltage isincreased by the AC chopper. However, the additional loss causedby the AC chopper occurs in the proposed system structure.
Further, it is confirmed that the efficiency of the proposed circuit
is higher than that of a BTB system on the basis of the loss
analysis(9). This is because the number of devices in the AC
chopper where the current passes through is 2/3 less than that of
the rectifier in a BTB system.
In this work, the validity of the proposed system in theadjustable speed drive system is evaluated in order to clarify theadvantage of the proposed system in comparison with theconventional MC. In order to drive the motor at the rated speed
and in the high torque region, there are three possible solutions: (i)application of flux-weakening control, (ii) boost-up of the voltage
by the AC chopper, or (iii) a combination of both the solutions (i)and (ii). In terms of the total loss, the proposed system withsolutions (ii) or (iii) is compared with the conventional MC byusing solution (i). A rated voltage of 180 V is used for the interior
permanent magnet (IPM) motor owing to the limitation in theexperimental conditions in order to verify the proposed converter.
In addition, the boost-up ratio of the AC chopper cannot be set
higher than 180 V. Therefore, flux-weakening control is necessary
in order to maintain the output voltage at the rated voltage in the
proposed system. Furthermore, the input voltage is degradedbecause the range of flux-weakening control in the proposedsystem is expanded when compared with the conventional MC. As
a result, the effectiveness of the proposed system is determined interms of the total loss.
The remainder of this paper is organized as follows. First, thechopper loss in the proposed system and the copper loss of the
motor in the conventional MC are described theoretically. Further,
the differences between the chopper loss and the copper loss are
determined through comparison, where flux-weakening control isimplemented in the motor control. Finally, the operation of the
proposed system is demonstrated with a 3.7-kW IPM motor
through simulation and experiment. In addition, the chopper loss
and copper loss are evaluated to clarify the validity of the
proposed system.

Fig. 1. Circuit configuration of a matrix converter with aboost-up chopper. In order to compensate the output voltage,a V-connection AC chopper is connected on the input side.
dominate the size and weight in comparison with the original
structure of an MC. In addition, the maximum output voltage ofthe proposed system is determined by the duty ratio of the AC
chopper in the boost mode. It should be noted that the switches in
the AC chopper do not operate when the output voltage is lower
than 0.866 times the input voltage. In other words, theV-connection AC chopper in the proposed system does not
generate switching loss in the low output voltage range.
However, conduction loss occurs in the AC chopper even when
the switching operation is disabled. Therefore, degradation of theconversion efficiency by adding the AC chopper is an issue ofconcern.
2.1 Conduction loss
In order to consider the influence of the chopper loss on the
proposed system, the chopper losses such as conduction loss andswitching loss are theoretically derived in this section.
First, the conduction loss of Sc1 is expressed as
Pcon _ S 1 

1



 0

vceir dt ...................................................... (2)where vce is the on-state voltage of Sc1, which is expressed by(3); and ir is the input current.

vce  k con1ir  k con 2 ............................................................ (3)2. Derivation of the chopper loss

It is noted that kcon1 and kcon2 are the coefficients defined fromthe on-state voltage characteristics mentioned in the datasheet ofthe switching device. In this paper, SK80GM063 manufactured by
SEMIKRON is used as the chopper device. The rated voltage andrated current of this IGBT are 600 V and 81 A, respectively. Fromthese equations, the conduction loss of Sc1 is introduced as

Fig.1 shows the proposed system in which a V-connection AC
chopper is connected in the input stage of the MC(10)(11). Eight
IGBTs are used in the AC chopper. Each of the bi-directionalswitches comprises two IGBTs. On the other hand, 18
reverse-blocking IGBTs (RB-IGBT) are used in the MC. The
relationship between the input voltage vin and the output voltage
vout is expressed as

Pcon _ S 1 

v out     mc  v in .............................................................. (1)k con1



2

I in 

2 2 k con 2

I in ................................... (4)where, Iin is the effective value of the input current. Similarly, theconduction loss of Sc2 is expressed bywhere mc is the voltage transfer ratio of the MC,  is the boost-up
ratio of the chopper and vin is the input voltage. Basically, thefunction of the AC chopper is to boost-up the input voltage.
Further, feedback control is not required for the filter capacitor
because the output of the chopper as in a PWM rectifier is not DC
voltage. Therefore, the capacitance and the inductance are notdominated by the voltage control response and the current
response from the input side, in contrast to those of a BTB system.
For this reason, it is not necessary to use a large inductor or an
additional inductor at the primary stage of the AC chopper. As aresult, the V-connection AC chopper and these components do not

Pcon _ S 2 (   1)k con1

2

I in 

2 2 (   1)k con2

I in ............. (5)It is noted that the equations concerning the conduction lossesof Sc4 and Sc3 are equivalent to (4) and (5), respectively.
2.2 Switching loss
Fig. 2 shows the integral period to calculate the switching loss.
The switching loss of the AC chopper is proportional to the
product of the capacitor voltage vcrs and ir. Moreover, the integral
period is different among the switching devices. In other words,
2

IEEJ Trans. ●●, Vol.●●, No.●, ●●●Evaluation of Boost-up Matrix Converter in Drive system(Kazuhiro Koiwa et al.)Table 1. Parameters used to calculate the chopper loss. The
parameters of the switching device are obtained from thedatasheet.

Fig. 2. Integral period of the switching loss of the AC
chopper. Switching loss occurs during different periods
among each switching device.
the integral period of Sc1 and Sc4 is from 5/6 to , whereas theintegral period of Sc2 and Sc3 is from /6 to . Thus, the switchinglosses Pton_s1 and Pton_s2 are expressed asv
1 
Pton _ S 1  5 eon f s rs dt

 6
Vs



2Vin f s(   1)[( 6  6)kton1I in  12( 3  2)kton 2 ]24Vs................................................................................................. (6)v
1 Pton _ S 2   eon f s rs dt
 6
Vs
(7)
2 Vin f s
[(5 6  3 2 ) kton1I in  12(1  3 )kton 2 ]24Vs

Fig. 3. Chopper loss, which includes the conduction loss
and switching loss, for the input current shown in thecalculation and simulation results. In order to evaluate thederived equation of the chopper loss, the calculation results
are compared with the simulation results.

where, Vs is the nominal voltage when the switching loss
characteristics mentioned in the datasheet are used, and fs is theswitching frequency of the AC chopper. Vin is the effective valueof the input voltage. In addition, eon is instantaneous switchingloss which is characterized by (8).

is necessary to apply flux-weakening control in motor control(3)-(6).
However, the copper loss of the IPM motor is increased because
the d-axis current flows according to flux-weakening control. In
this section, the control strategy of the proposed system, that is,flux-weakening control is explained. Additionally, the equation of
the copper loss, which is increased by the flux-weakening control,
is expressed corresponding to the d-axis and q-axis currents.
3.1 Control strategy of the proposed system
Fig. 4 shows the control block diagram of the proposed system.
First, the duty command of the chopper dc* for the V-connection
AC chopper is expressed byeon  kton1ir  kton 2 ............................................................. (8)It is noted that kton1 and kton2 are the coefficients defined fromthe switching loss characteristics mentioned in the datasheet of theswitching devices. Furthermore, the equations concerning theswitching loss of Sc4 and Sc3 are equivalent to (6) and (7),respectively.
In order to validate these equations, the calculation results arecompared with the loss simulation results, which are obtained by
PSIM. Table 1 lists the calculation parameters. In the loss
simulation, the circuit configuration includes only the AC chopper,
and the current source is used as the load. In addition, the strayinductance and stray capacitance are not taken into consideration.
Fig. 3 shows the conduction and switching losses of the AC
chopper obtained by theoretical calculation and simulation(12). It isnoted that the chopper loss shown in the calculation results is thesum of (4), (5), (6), and (7). As a result, the calculation results
agree well with the simulation results. Thus, the validity of thederived equations of the chopper loss is confirmed. In other words,
the chopper loss is easily calculated from the input current.

*

dc 

mc
vc

*

......................................................................... (9)where vc* is the voltage command, which is converted from therotating speed command. In this work, mc is considered as thelimitation of the voltage transfer ratio of the MC, which is 0.866.
Although, the voltage transfer ratio in the proposed system isimproved by the AC chopper, resonance distortion due to the input
filter occurs. Therefore, damping control is applied in the AC
chopper control(9).
On the other hand, the pulse pattern of the MC is generated by
the virtual indirect control method(13). The virtual indirect control
method is divided into input current control and output voltage
control. Thus, the conventional control method is applied for eachcontrol. The input current commands icd* and icq* are generated

3. Derivation of the copper loss of the IPM motor
As an IPM motor is driven in the high rotating speed region, it
3

IEEJ Trans. ●●, Vol.●●, No.●, ●●●Evaluation of Boost-up Matrix Converter in Drive system(Kazuhiro Koiwa et al.)p*  vcd  q*  vcq
2

vcd  vcq2p  vcq  q*  vcd

it.................................................. (10)*2vcd  vcq

2*
Chopperf/V Vccommand cal.
conv.
eq.(9)...................................................(11)**where, p is the active instantaneous power command and q is thereactive instantaneous power command. It is noted that p* is equal
to 1 p.u., and q* is equal to 0 p.u. in this work, in order to obtain
unity power factor. In addition, vcd and vcq are the d-axis andq-axis capacitor voltages, respectively.
In order to drive the IPM motor in a high rotating speed area
within the output voltage limitation of the MC, it is necessary toapply flux-weakening control in MC control. This is because theback electromotive force increases with increasing rotating speed.
The output voltage, which is necessary to control the motor, isdegraded by flux-weakening control. Therefore, the d-axis current
id for the flux-weakening control is introduced.
Fig. 5 shows the vector diagram of flux-weakening control,
where eq is the back electromotive force, and v and v’ are theterminal voltages in the IPM motor without and with
flux-weakening control, respectively. It is noted that the winding
resistance of the IPM motor Rw is not considered. The
flux-weakening control in the IPM motor equally weakens themagnetic flux in the permanent magnet from the d-axis armaturemagnetic flux. As a result, the rotating speed area is extended by
implementing flux-weakening control. As shown in Fig. 5, Vom,
which is the maximum output phase voltage of the MC, isexpressed by (12).
2

V om  v d  v q

Kd

pg

*

icq 

Damping control
dq i
cq
/
HPF
3

vcr
vct

vcd
icd**
vcq
imid*
icq
Input
current
2 command cal. 2 dq 3/
imid_sign*eq.(10), eq.(11)3 ir*
is
Fluxit*id *18
vd*
weakening
ACR
dq
control eq.(13)3/ 3**
vq* 3 vu*
v
u
ASR *
ACR
vv**
vv**
iq
vw**
vw
dq iq
/ i
d
3
Virtual indirectcontrol
Vector control(b) Matrix converterdq/
3Inverter
controliq

iu
iw

Sc1 Sc4
Sc2 Sc3

Carrier(a) AC chopper

Fig. 4. Control block diagrams of the (a) AC chopper and (b)MC. Damping control is applied to the AC chopper control tosuppress the input filter resonance. The motor is driven byvector control. In MC control, virtual indirect control isapplied. The MC with a boost-up chopper is easily controlled
because both chopper control and MC control are
independent.

2 (L q i q ) 2  (L d i d  e q ) 2

Dd
DC* +
+

Rectifiercontrol

*

icd 

ir

PWM Composition for MCfrom the capacitor voltage in order to maintain a constant output
power(14). Thus, these parameters are expressed as........................................ (12)Therefore, the d-axis current in the flux-weakening control at
the maximum voltage is calculated by (13).
 eq  Vom  (Lq i q ) 2
2

id 

Ld

....................................... (13)3.2 Copper loss caused by flux-weakening control
The motor is driven in the high rotating speed region byflux-weakening control. However, the motor current is increased
owing to flux-weakening control. As a result, the motor loss andthe converter loss increase. In order to validate the AC chopper, it
is evinced that the copper loss is decreased by the proposedsystem. In particular, the equation for the copper loss subject tothe input line voltage is calculated.
First, the torque of the IPM motor is expressed byT  Pn [eq

Fig. 5. Vector diagram of flux-weakening control. In orderto suppress the output voltage, the negative d-axis current
flows. The motor is driven at a high rotating speed byflux-weakening control.

iq  ( Ld  Lq )id iq ] ........................................ (14)where, Pn is the number of pole pairs. As shown in (14), the torqueof the IPM motor depends on the d-axis and q-axis currents.
As shown in (13) and (14), the d-axis and q-axis currents
depend on Vom. Additionally, Vom is determined by the input line
voltage and voltage transfer ratio. In other words, in order tocalculate the copper loss of the motor as Vin is changed, the q-axis
current is introduced for Vom. Thus, Vom is expressed by (15) using(13) and (14).

Vom  [

Ld
T Lq
1
(

eq iq ) ]2  (Lq iq ) 2 ...... (15)
( Ld  Lq ) Pn Ld
iq

It is noted that the q-axis current should be obtained to derive
the copper loss. However, (15) cannot obtain the q-axis current.
For this reason, the q-axis current is calculated by numericalanalysis. It should be noted that the q-axis current is limited by(16).
4

IEEJ Trans. ●●, Vol.●●, No.●, ●●●Evaluation of Boost-up Matrix Converter in Drive system(Kazuhiro Koiwa et al.)

iq 

Vom

Lq

Table 2. IPM motor parameters. The copper loss iscalculated from these parameters.

...................................................................... (16)On the other hand, the d-axis current is calculated by (13).
Therefore, the copper loss Pc is expressed by2

2

Pc  3Rw I o  3  Rw 

2(id  iq )2..................................... (17)where, Rw is the primary winding resistance of the IPM motor. In
addition, Io is the R.M.S. of the output current.
3.3 Comparison of the chopper loss with the copper loss
Fig. 6 shows the calculation results of the comparison between
the additional chopper loss and the additional copper loss due toflux-weakening control. It is noted that the copper loss iscalculated by the motor parameters, which are listed in Table 2.
The input line voltage Vin is changed. Furthermore, the additional
copper loss in Fig. 6 is obtained by subtracting the copper loss,
which occurs in the conventional MC PC_CMC, from that of the
proposed system PC_BMC. The copper loss of the proposed systemdoes not depend on the input voltage because the constant output
voltage of 180 V is controlled by the AC chopper. In addition,
application range of flux-weakening control in the IPM motor is
not wide. Therefore, in order to extend the application, the input
voltages of the proposed system and the conventional MC aredegraded. Further, it is possible to simulate the high rotating speedof the IPM motor. As a result, the range of the additional copper
loss (PC_CMC - PC_BMC) is negative. This is because the phase of the
motor current increases when controlling the d-axis current. As aresult, the power factor of the motor is improved, and the output
current decreases. Therefore, the copper loss in the conventional
MC is lower than that of the proposed system. Additionally, thechopper loss is greater than the copper loss when the ratio between
the rated motor voltage Vn and Vin (Vn/Vin) is less than 1.01 p.u..
On the other hand, as Vn/Vin is greater than 1.01 p.u., the chopper
loss is lower than the copper loss. This is because the motor
current and the copper loss increase owing to flux-weakening
control when Vn/Vin is higher.
Therefore, as the motor parameters and the switching device
characteristics are known, the effective region of the AC chopperis calculated by (4), (5), (6), (7), (13), and (15). In other words, it
is not necessary to analyze the total loss by experiment. In termsof efficiency, the effectiveness of the proposed system isdetermined by only referring to the motor and device parameters
without an experiment.

Fig. 6. Loss comparison between the additional loss byflux-weakening control and the AC chopper when the
input line voltage is changed. The rated motor voltage is
180 V and constant. When the motor and device
parameters of the chopper are well-known, theeffectiveness of the boost-up chopper can be calculated.
respectively. Accordingly, the motor is driven without
flux-weakening control by the proposed system because thevoltage is increased to 240 V. On the other hand, in order to drive
the motor at a high speed and in the high-torque region with theconventional MC, flux-weakening control is necessary because theoutput voltage of the conventional MC is limited to 173 V.
Fig. 8 shows the experimental acceleration tests conducted on
the IPM motor, which is driven by the proposed system with
vector control. It is noted that a four-step commutation sequence,
which uses the voltage of the filter capacitors, is applied to theexperiment(15). As shown in Fig. 8, the AC chopper operates while
the rotating speed * is greater than 360 r/min in order to suppress
the input filter resonance by damping control. Additionally, it isconfirmed that the input and q-axis currents are not drasticallychanged as the AC chopper begins operating. Therefore, theproposed system continuously improves the voltage transfer ratioof the MC.
Fig. 9 shows the steady operation of the IPM motor, which isdriven at a rated torque by the proposed system. It is noted that
damping control is applied in the AC chopper. Moreover, in orderto reduce commutation errors, a hybrid commutation which
combines voltage and current commutations, is adopted. In
addition, the boost-up ratio of the AC chopper and the input line
voltage are set to 1.15 and 180 V, respectively. Furthermore, inorder to confirm the fundamental operation of the proposedsystem, the motor speed is controlled at a rated rotating speed by
the load-side motor. In other words, an automatic speed regulator(ASR) is not used.

4. Simulation and experimental results
4.1 Fundamental operation of the proposed system by the
IPM motor load
In this section, the accelerated operation and the steady
operation of the IPM motor are implemented through simulationand experiment. Table 3 summarizes the conditions for thesimulation circuit and the experiment. It is noted that the output
line voltage is observed by a low-pass filter (LPF) with a 1.5-kHz
cut-off frequency in order to observe the low-frequency
component distortion.
Fig. 7 shows the operation waveforms of the proposed systemand the conventional MC. It is noted that the input line voltage is
200 V. In addition, the rated voltage of the motor is set to 240 V.
The rotating speed and the d-axis and q-axis currents arenormalized at the synchronous speed and rated current,
5

IEEJ Trans. ●●, Vol.●●, No.●, ●●●Evaluation of Boost-up Matrix Converter in Drive system(Kazuhiro Koiwa et al.)Fig. 7. Acceleration test and transient response of the load torque for (a) the conventional MC and (b) the proposed system
shown in the simulation results. The rotating speed of the motor is 2000 r/min. It is assumed that the rated voltage of the motor
is 240 V. The output voltages of the conventional MC and proposed system are limited to 173 V and 240 V, respectively.
Table 3. Simulation and experimental conditions.

Fig. 9-(a) shows the static operation waveforms of the proposedsystem. According to the waveforms, it is confirmed that thed-axis and q-axis currents are maintained at a constant value by
the automatic current regulator (ACR). On the other hand, the total
harmonic distortion (THD) of the input current is 6.6%.
Fig. 9-(b) shows the spectrum of the input current obtained by afast Fourier transform (FFT). It is noted that the input current
value is normalized to the fundamental current, which is equal to12.9 A. In addition, fi and fo are the input and output frequency,
respectively. According to the FFT results, large harmonic
distortion does not occur. However, the spectrum of the input
current occurs at 6fi - fi and 6fi + fi owing to the dead-time error.
Fig. 10 shows the output line voltage characteristic based on the
output power of the motor. In this work, flux-weakening control isapplied at a voltage within the rated voltage of the motor when theload torque is changed at the rated speed. It is noted that the input
line voltage is set to 180 V. The rated voltage of the IPM motor Vn
is 180 V. Thus, it is necessary to limit the output line voltage to
180 V by flux-weakening control. According to these results, it isconfirmed that the output line voltage is limited to 180V byapplying flux-weakening control. Thus, flux-weakening control isvalidated by the experimental results. When the load torque ischanged at the rated speed of the motor, flux-weakening control isapplied at an output power of the motor of 1.3 kW in the proposedsystem. On the other hand, flux-weakening control is applied at an
output power of the motor of 400 W in the conventional MC. In
other words, as soon the output power of the motor exceeds a
400-W load, the d-axis current increases owing to flux-weakening
control in the conventional MC. As a result, the copper loss of theIPM motor is increased owing to flux-weakening control.
Fig. 11 shows the converter efficiency characteristic and the
input power factor characteristic, proportional to the output powerof the MC. First, it is confirmed that the unity power factor is
obtained at an output power greater than 1 kW. On the other hand,the converter efficiency at the maximum point is 94.8% at an
output power of 2.3 kW.

Fig. 8. Experimental acceleration test by the MC with aboost-up chopper. The acceleration time is 0.3 s. The
boost-up AC chopper operates when the rotating speed isgreater than 360 r/min.
Fig. 12 shows the input current THD characteristic for the
output power of the converter. It is noted that the current-type
damping control is applied to the AC chopper in all regions.
Moreover, the hybrid commutation, which is a combination of the
6

IEEJ Trans. ●●, Vol.●●, No.●, ●●●Evaluation of Boost-up Matrix Converter in Drive system(Kazuhiro Koiwa et al.)Fig. 9. Steady operation at the rated torque by experiment. The hybrid commutation is applied in the AC chopper and the MC.
These figures show (a) the operation waveforms and (b) the spectrum of the input current by FFT. The spectrum of the input current
is normalized at 12.9 A. The polarity of the d-axis current is reversed. The input current THD is 6.6 %. The effective value of theoutput line voltage is 180 V owing to flux-weakening control. One of main causes of input current distortion is the dead time error.

Fig. 11. Converter efficiency and input power factor
characteristics of the proposed system. The converter
efficiency at the maximum point is 94.8 % at an output
power of 2.3 kW. The input power factor at the maximum
point is 0.994 at an output power of 1.8 kW.

Fig. 10. Output line voltage characteristic obtained with
flux-weakening control in the proposed system andconventional MC. The rated motor voltage and input line
voltage are 180 V. As a result, the output line voltage islimited to 180 V by flux-weakening control.
voltage commutation and the current commutation(15), is applied in
the AC chopper and MC. Furthermore, optimal design the gain isrequired for damping control.
From these results, the validity of the proposed system in theadjustable drive system is confirmed.
4.2 Loss analysis of the conventional MC and the
proposed system
In order to validate the proposed system in terms of efficiency,
the total loss characteristic of the proposed system is comparedwith that of the conventional MC through simulations andexperiments.
Fig. 13 shows the d-axis current and q-axis current
characteristics for Vn/Vin. It is noted that the experimental results
are obtained by the conventional MC. In order to validate theequation of the copper loss, the calculation results are comparedwith the experimental results. As shown in Fig. 13-(a), thecalculation results almost agree with the experimental results. On
the other hand, as shown in Fig. 13-(b), the error between thecalculation results and the experimental results is approximately
10%. This error is because the winding resistance of the IPM
motor is not considered in (13). However, the trend in thecalculation result almost agrees with the experimental result. Thus,

Fig. 12. Input current THD characteristic in the proposed system.
The damping gain Kd is 0.5 (p.u.). The input current THD is below
7 % in all regions. The minimum THD of the input current is
4.8 % at an output power of 2.6 kW.
the validity of the equations for the copper loss is confirmed.
Additionally, as Vn/Vin increases, the d-axis current increases. Thisimplies that the compensation value of flux-weakening control
increases with Vn/Vin. On the other hand, the q-axis current
decreases as Vn/Vin increases. According to (14), the q-axis current
decreases when the d-axis current increases when the torque is
7

IEEJ Trans. ●●, Vol.●●, No.●, ●●●Evaluation of Boost-up Matrix Converter in Drive system(Kazuhiro Koiwa et al.)Fig. 14. Loss property in the simulation results showing the total
loss comparison between the conventional MC (left side) and the
proposed system (right side) with/without flux-weakening control.
The rated voltage of the motor is 240 V. In comparison with theconventional MC, the total loss of the proposed system decreases
by 60 % because flux-weakening control is not applied.

Fig. 13. d-axis current and q-axis current comparison between thecalculation and the experimental results in the conventional MC.
The error between the calculation and experimental results iswithin 10 %. The calculation results of the d-axis current andq-axis current agree with the experimental results.
constant.
Fig. 14 shows the loss property determined through simulation.
It is noted that the rotating speed is 2000 r/min, the output powerof the motor is 2 kW, and the input line voltage is set to 200 V. In
practice, the output voltage of the converter cannot be higher
because it is assumed that the rated motor voltage is greater thanthat of the actual motor in the simulation. Therefore, the rated
motor voltage is set to 240 V in the simulation. According to theresults, the converter loss of the proposed system is increased
owing to the AC chopper. However, taking the IPM motor loss
into consideration, the total loss in the proposed system is lessthan that in the conventional MC. This is because the copper lossof the IPM motor, the conduction loss of the free wheeling diodes(FWDs) and the conduction loss of the IGBTs are increased owing
to flux-weakening control in the conventional MC. Therefore,
when the rated voltage of the motor is increased, the effective areaof the proposed system can be expanded.
Fig. 15 shows the total loss comparison between the proposedsystem and the conventional MC. It is noted that Vin is changed.
The total losses, as shown in Fig. 15, between the proposedsystem and the conventional MC are compared with regard to theeffective areas of both systems. Additionally, the iron loss and themechanical loss Pother are expressed by (18) in the experiment.

Fig. 15. Total loss comparison between the conventional MC andthe proposed system. The calculation results agree with theexperimental results. In the case that Vn/Vin is greater than 107 %,the total loss in the proposed system is less than that in theconventional MC. The validity of the proposed system isdetermined when the input line voltage is below 93.5 % of the
rated motor voltage.
flux-weakening control.
On the other hand, the AC chopper in the proposed systemeasily improves the already decreased input line voltage. For thisreason, high efficiency of the proposed system is achieved in theadjustable drive system.
According to the experimental results, when the ratio of the
input line voltage and the rated motor voltage is greater than 1.07
p.u., the total loss of the proposed system is less than that of theconventional MC. However, in comparison with Fig. 6, the turning
points in both the results are different. Further, the error between
the calculation results and the experimental results is 5.6 %. Thisis because the iron loss and mechanical loss is not taken into
consideration, as shown in Fig. 6. The iron loss depends on the
output line voltage and frequency. Therefore, the validity of thePother  125  (Vn / Vin )  308 ......................................... (18)
Accordingly, the total efficiency of the conventional MC, whichapplies flux-weakening control, becomes low as the input line
voltage decreases. This is because the conduction loss of theconverter and the copper loss of the IPM motor increase owing to
8

IEEJ Trans. ●●, Vol.●●, No.●, ●●●Evaluation of Boost-up Matrix Converter in Drive system(Kazuhiro Koiwa et al.)

(2)

(3)

(4)

(5)

(6)

Fig. 16. Relationship between the turning point of Vn/Vin and theoutput power of the motor Pm by calculation result. The turning(7)

point of Vn/Vin is the point that the total loss of the proposedsystem is lower than that of the conventional MC.

(8)proposed system is determined as the rated motor voltage exceeds
107 % of the input voltage.
Fig. 16 shows the relationship between the turning point of
Vn/Vin and the output power of the motor. From this result, it isobserved that the turning point of Vn/Vin, which denotes theeffectiveness of the proposed system, is reduced when the output
power of the motor is increased. This is because the total
efficiency of the conventional MC is drastically degraded incomparison with the proposed system when the output power ofthe motor is increased. Thus, when the output power of the motor
is increased, the effectiveness of the proposed system is expanded.
In particular, it is noted that the efficiency of the proposed system
is higher than that of the conventional MC at the rated output
power of the motor when the rated motor voltage is greater than
90 % of the input voltage.
Finally, when a high rated voltage of the IPM motor is applied,the effective region of the proposed system is theoreticallycalculated from the abovementioned equations.

(9)

(10)
(11)

(12)

(13)

(14)

(15)

Kazuhiro Koiwa(Student Member) received
his B.S. and M.S. degrees in electrical, electronics
and information engineering from Nagaoka
University of Technology, Nagaoka, Japan in 2010
and 2012, respectively. Since 2012, he has beenwith Nagaoka University of Technology as a PhD
degree student in electrical and electronics
engineering. His research interests include AC-AC
converters for renewable energy field and motor drive system. He is a
student member of the Institute of Electrical Engineers of Japan.

5. Conclusion
In this work, the validity of the proposed system was evaluatedin terms of the efficiency of the IPM motor drive system.
Consequently, the chopper loss and copper loss were derived
theoretically. Further, the calculation results of the chopper loss
agree with the simulation results. On the other hand, the error in
the copper loss between the calculation results and the simulation
results is less than 10%. As a result, it was confirmed that the
chopper loss is less than the copper loss with regard to theeffective area.
The proposed system was demonstrated with a 3.7-kW IPM
motor. As a result, it was confirmed that the converter efficiencyof the proposed system is 94.8 % at a mechanical output power of
2.3 kW. Moreover, the validity of the proposed system wasconfirmed as the input voltage is below 93.5 % of the rated motor
voltage.
In our future work, the damping gain will be optimized.
Moreover, the harmonic distortion in the input current will be
suppressed.

Jun-ichi Itoh

(Member) received his M.S.

and PhD degrees in electrical and electronicsystems engineering from Nagaoka University ofTechnology, Nagaoka, Japan in 1996 and 2000,
respectively. From 1996 to 2004, he was with Fuji
Electric Corporate Research and Development Ltd.,Tokyo, Japan. Since 2004, he has been with
Nagaoka University of Technology as an associate
professor. He received the IEEJ Academic Promotion Award (IEEJ
Technical Development Award) in 2007. His research interests include

References(1)

Electronics Vol. 49, No. 2, pp274-288, 2002.
Q. Lei, F.Z.Peng, B. Ge: "Pulse-Width-Amplitude-Modulated Voltage-Fed
Quasi-Z-Source Direct Matrix Converter with maximum constant boost", ,Vol. , No. , pp. 641-646 (2012)
D. Casadei, M. Mengoni, G. Serra, A. Tani, L. Zarri: "Assessment of an
Induction Motor Drive for High Speed Operation based on Matrix
Converter", EPE2007, Vol. , No. , pp. (2007)
Ki-Chan Kim : "A Novel Magnetic Flux Weakening Method of Permanent
Magnet Synchronous Motor for Electric Vehicles", IEEE Trans., Vol. 48,
No. 11, pp. 4042 - 4045 (2012)
Shinn-Ming, Sue, Ching-Tsai Pan: “Voltage-Constraint-Tracking-Based
Field-Weakening Control of IPM Synchronous Motor Drives", IEEE
Transactions on Industrial Electronics, vol. 55, no. 1, pp. 340-347, 2008
S. Chaithongsuk, B. Nahid-Mobarakeh, N. Takorabet, F. Meibody-Tabar:"Optimal Design of Permanent Magnet Motors to Improve
Field-Weakening Performances in Variable Speed Drives", IEEE Trans., Vol.
59, No. 6, pp. 2484-2494 (2012)
Zbigniew Fedyczak, Pawel Szczesniak, Igor Korotyeyev; “New Family of
Matrix-Reactance Frequency Converters Based on Unipolar PWM AC
Matrix-Reactance Choppers”EPE-PEMC 2008, P170 pp.236-24
Zbigniew Fedyczak, Pawel Szczesniak, Marius Klytta; “Matrix-ReactanceFrequency Converter Based on Buck-Boost Topology”, EPE-PEMC 2006,
pp.763-768
K. Koiwa, J. Itoh: "Experimental Verification of Effectiveness of Boost-up
Matrix Converter with V-connection AC Chopper", IEEJ Trans. D, Vol. 132,
No. 1, pp. 1-8 (2012)
J. Itoh, H. Tajima, H. Ohsawa: “Induction Motor Drive System using
V-connection AC Chopper”, IEEJ Trans., Vol.123, No.3, pp.271-277 (2003)
T.Shinyama, M. Kawai, A. Torii, A. Ueda: “Characteristic of an AC
Chopper Circuit with LC Filters in the Input and Output Side”, IEEJ Trans.,
Vol.125-D, No.3, pp.205-211 (2005)
J. Itoh, T. Iida, A. Odaka:" Realization of High Efficiency AC link
Converter System based on AC/AC Direct Conversion Techniques with
RB-IGBT" Industrial Electronics Conference, Paris, PF-012149,2006
J. Itoh, I. Sato, H. Ohguchi, K. Sato, A. Odaka and N. Eguchi: “A Control
Method for the Matrix Converter Based on Virtual AC/DC/AC Conversion
Using Carrier Comparison Method”, IEEJ Trans., Vol.124-D, No.5,
pp.457-463 (2004)
I. Sato, J. Itoh, H. Ohguchi, A. Odaka, and H. Mine: “An Improvement
Method of Matrix Converter Drives Under Input Voltage Disturbances”,
IPEC-Niigata, pp. 546–551 (2005)
K. Kato, J. Itoh: ”Development of a Novel Commutation Method which
Drastically Suppresses Commutation Failure of a Matrix Converter,”Trans.IEEJ,Vol.127-D,No.8,pp.829-836,2007

matrix converters, DC/DC converters, power factor correction techniquesand motor drives. He is a member of the Institute of Electrical Engineers

P. W. Wheeler, J. Rodriguez, J. C. Clare, L. Empringham: ”Matrix
Converters: A Technology Review” IEEE Transactions on Industryof Japan.

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