Verification of Effectiveness of a Matrix Converterwith Boost-up AC Chopper by Using an IPM Motor
Kazuhiro Koiwa

Jun-ichi Itoh

Electrical, Electronics and Information Engineering
Nagaoka University of Technology
Nagaoka, Japan
newkoiwa@stn.nagaokaut.ac.jp

Electrical, Electronics and Information Engineering
Nagaoka University of Technology
Nagaoka, Japan
itoh@vos.nagaokaut.ac.jp

Abstract— This paper describes the matrix converter thatfeatures boost-up functionality. The proposed circuit topology
connects a V-connection AC chopper at the input side of thematrix converter to achieve the boost-up function. The matrix
converter and the V-connection AC chopper are controlled
independently, where a virtual indirect control method isapplied to the matrix converter, and an open-loop control isapplied to the V-connection AC chopper. However, theefficiency of the proposed circuit is low due to the extra loss
from the V-connection AC chopper. In this paper, the efficiencyof the proposed circuit and the conventional matrix converter isevaluated by using a 3.7kW IPM motor in the simulation andthe experiment. The simulation results confirm that byimplementing field-weakening control in the conventional
matrix converter, the losses are lower than that of the proposed
circuit topology, where the proposed circuit improves theefficiency by 12%. According to the experimental results, it isobtained that the proposed circuit can improve the efficiency of
13% in compare with the conventional matrix converter.

I.

INTRODUCTION

Matrix converters (MC) which can convert an AC power
supply voltage directly into an AC output voltage of variable
amplitude and frequency without the large energy storages,
such as electrolytic capacitors, have been actively studied
recently [1-15]. The following shows the advantages of thematrix converters comparing with the back-to-back converter
system (BTB system), which is consist of a PWM rectifier anda PWM inverter; (i) light-weight and long-life due to no large
passive components in the main circuit and (ii) high efficiency
because of fewer switching devices are connected in thecurrent path. The MC is expected to apply in the renewableenergy field such as the hybrid electric vehicle systems, wind
power generator systems and others.
However, the MC has a drawback in the voltage transfer
ratio, which defines as the ratio between the output voltage
and the input voltage, is being constrained to 0.866.
Consequently, the output current of the MC is higher than thatof the BTB system, under the same output power. Even the
motor can drive at rated frequency as the field-weakening
control is applied. However, the output current is increased
and the efficiency of the system is reduced. Further, the motor
loss increases due to the high input motor current. Besides, therestricted voltage transfer ratio also limits the applications of
the MCs.
There are many literatures which discuss on improving thevoltage transfer ratio of the MCs. One of the easy solutions is
to connect a transformer between the power supply and theMC. However, the commercial frequency transformer applies
in the power grid frequency gives penalty in term of weightand size.
There are papers studied to apply over-modulation in the
MC and successfully improved the voltage transfer ratio from
0.866 to 0.94 [13][14]. However, the input current and theoutput voltage contain large amount of harmonic components
due to the square waveforms. Additionally, the amplitude of
output voltage is lower than the input voltage. In other words,
the MC cannot apply for the high voltage application.
Therefore, in considering of applying the MC in the near
future of power electronics fields, the boost-up functionality
stands an important role.
On the other hand, a Matrix-Reactance Frequency
Converter (MRFC), which consists of a MC and an AC
chopper, has been studied in [12]. Reference [12] shows that,the amplitude of the output voltage can control to extend
which is higher than the input voltage. However the MRFC
requires many components due to the insertion of the boost up
reactor and capacitor. In addition, the control becomescomplicated due to the requirement of regular synchronizing
between the MC and the chopper.
This paper demonstrates the matrix converter circuit
topology which connects the V-connection AC chopper at the
input side of the MC [3][15]. The additional component of thiscircuit is only consisting of the bi-directional switches because
the reactors in the input filter are being used as boost-up
reactors in this method. Also, the automatic voltage controller

(AVR) for the chopper is not required in this system. As aresult, the value of the capacitor needed in the boost-stage issmaller than that of the DC capacitor in a BTB system.
Moreover, the origin advantages of the MC remain in the
proposed circuit because the V-connection AC chopper isideal (no switching operation) when the output voltage islower than the maximum value of the voltage transfer ratio(0.866). However, the proposed circuit has two problems suchas following. At first, the input current distorts due to the input
filter resonance. Secondary, in comparison with theconventional MC, the efficiency of the proposed circuit isdegraded due to the chopper loss.

Fi
gure 1. Circuit configuration of the proposed circuit.

In this paper, the proposed circuit is simulated andexperimented by using a 3.7kW-Interior Permanent Magnet
motor (IPM motor). At first, in order to suppress the input
filter resonance, the input current stability control is applied in
the chopper. Secondary, in the simulation, the control applies
with the field-weakening control, and compares the efficiencyof the system by using the proposed circuit with theconventional MC. Finally, the validity of the simulation
results will be confirmed by experiment.
II.

CIRCUIT TOPOLOGY

Figure 1 shows the proposed circuit diagram. The
proposed circuit connects a V-connection AC chopper at the
input side of the MC. The additional components are based oneight IGBTs that are mainly constructed by silicon and diodes.
The relationships between the input voltage vin and the output
voltage vout is expressed by vout   chop  mc  vin where, mc is the modulation index of the MC, chop is theboost-up ratio of the chopper and vin is the input voltage. The
proposed circuit does not require a voltage control for the
input capacitor. Therefore, the capacitor value does not
dominant by the voltage control response and the current
response for the input side. As a result, the V-connection AC
chopper and the components do not dominate the size and theweight in comparison to the origin structure of a MC.
The maximum output voltage of the proposed circuit isdecided by the duty ratio of the V-connection AC chopper. It
should be noted that the switches in the V-connection AC
chopper is ideal (no operation) when the voltage transfer ratio
is lower than 0.866 of the input voltage. That is, at the rangeof low output voltage, the switching losses does not occur.
Besides, since the MC uses bi-directional switches, arerequired to apply with commutation pattern to prevent thesource and load from open circuit and short circuit. In thispaper, the 4-step commutation method is applied in the
proposed circuit. Moreover, the voltage of the filter capacitors
is used in this commutation [8].

Figure 2. Control diagram in the chopper.

III.

CONTROL STRATEGY

A. Boost-up Chopper Control
Figure 2 shows the control diagram in the chopper with thedamping control. The voltage command Dc* for the Vconnection AC chopper is expressed by


*

Dc 

mc
Vc

*





where, Vc* is the voltage command which is converted
from the rotating speed command.
In order to suppress the oscillation in the input current
from the resonance of the input filter, a stabilization control
for the matrix converter has been proposed in Reference [5][6]. In these papers, the distortion component of the terminal
voltage is removed by using a band pass filter (BPF). After
that, the distortion components are subtracted by the input
current command. In this paper, the input current stability
control is applied to the chopper instead of the matrix
converter. The damping control is implemented on the d-q
frame of the AC chopper control. The fundamental frequency
component on the d-q frame becomes a constant value, i.e. DC
signal. In addition, the harmonics components are appeared as
ripple components. The distortion component of the input
current icq is extracted by using a high pass filter (HPF). After
that, the distortion component is added to the choppercommand Dc*.
The damping control operates for the distortion component
as the feedback regulator. On the other hand, the fundamental
component is not affected. For this reason, the chopper control
does not require the high speed response [10]. It means thatthe filter capacitor and the boost-up reactor are not dominatedFigure 3. Control block diagram of the proposed circuit.

by the control response of the input current and the capacitor
voltage.

1
1  sTi

B. Matrix Converter Control
Figure 3 shows the control block diagram of the MC. In
this paper, the vector control is constructed from the ACR(Automatic Current Regulator) and the ASR (Automatic
Speed Regulator). In addition, the pulse pattern of the MC isgenerated by the virtual indirect control method [2]. The input
current command icd* and icq* are generated from the capacitor
voltage [5]. Thus, they are expressed by (3) and (4),respectively.




*

icd 

*

icq 

p  vcd  q  vcq
2

vcd  vcq2

vcd  vcq1  sTi
sTi

1Ra  sLa

1  sTsp

1
sJ m

sTsp

Figure 4.Vector control diagram of the MC.

K sp K T

p  vcq  q  vcd
2



Ks

KI

2





where, p is the active power command, q is the reactive
power command.



G ASR *

Tsp J m
K
K
K sp K T
sp T
2
s 
s
Jm
Tsp J m

where, the transient response of the ACR is faster than the
ASR and the equation (6) is calculated by equaling the gain
Figure 4 shows the vector control block diagram of the of the ACR to 1. Also, Ksp and Tsp are the proportional gain
MC. Figure 4-(a) and 4-(b) show the control block diagram of and the integrated time of the ASR, respectively. KI and TI are
ACR and ASR, respectively. The transfer function of the ACR the proportional gain and the integrated time of ACR,
and the ASR are expressed by (5) and (6), respectively.
respectively.
C. Field-weakening Control
KI
Figure 5 shows the vector diagram of the field-weakening
Ti La
I


 control where eq is the back electromotive force, v and v’ are
G ACR  * R  KIKI
the terminal voltage in the IPM motor without the fields2  as Iweakening control and with the field-weakening control.
La
Ti La
Field-weakening control in the IPM motor can equally
weaken the magnetic flux in the permanent magnet from thed axis armature magnetic flux. As a result, the rotation speed
area can be extended by implementing the field-weakening
control. From the figure 5, it is expressed by (7).

2

Vom  v d  v q2

 (Lq iq ) 2  (Ld id  eq ) 2

6-(a), q-axis current is decreased in comparison with Figure 6 (b) due to the d-axis current. Besides, it is confirmed that theoutput voltage is higher in compared with the conventionalMC.
Figure 7 shows the operation waveforms of the proposed
circuit. Figure 7-(a) shows the operation waveform without
applying the input current stability control method in the
chopper. Then, the total harmonic distortion (THD) of the
input current and output voltage THD are 18.9% and, 7%
respectively. It is confirmed that the resonance distortionoccur in the input current waveform. On the other hand,where, Vom is the limited value of the output voltage.
Therefore, d axis current is calculated by (8).



id 

eq



V
 ( om ) 2  ( Lq iq ) 2



Ld



Table 1 shows the parameter of the IPM motor in thispaper.
IV.

SIMULATION AND EXPERIMENTAL RESULTS

A. Operation of the proposed circuit
Figure 6 shows the operation waveforms of the proposed
circuit and the conventional MC (CMC). Table 2 provides theconditions for the simulation circuit and the experiment. The
rotating speed, d and q axis current are standardized at thesynchronous speed and the rated current, respectively.
According to Figure 6-(a), it is confirmed that field-weakening
control is applied in the MC at the high rotation speed area.
On the other hand, in Figure 6-(b), the d-axis current showsthat the field-weakening control is not applied in the highrotation speed. The torque occurred by the IPM motor isexpressed by (9).
T  Pn [ aiq  ( Ld  Lq )id iq ] Figure 5.Phaser vector diagram on the field-weakening control.
TABLE 1 MOTOR PARAMETERS.

where, Pn is pole of the motor. In addition, a is themagnetic flux by the permanent magnet. According to thisequation, the torque of the IPM motor is not only depended on
the q-axis current but also the d-axis current. Thus, in Figure

Figure 6. Operation waveforms in the simulation result.

TABLE 2 SIMULATION PARAMETERS.

TABLE 3 EXPERIMENTAL PARAMETERS.

Figure 7. Effectiveness of stability control.

Figure 7-(b) shows the operation waveform, where thedamping controls is applied in the AC chopper to suppress theresonant distortion. For these results, it is confirmed that theoutput voltage can increase to 27 V. Furthermore, the input
current THD and output voltage THD can be improved to
7.8% and, 1% respectively.
Figure 8 shows the acceleration and deceleration tests for
the IPM motor by using the proposed circuit. Table 3 showsthe experimental parameters. In Figure 8(a), the AC chopper isoperating while the rotating speed command * is over 0.9pu
because the voltage transfer ratio of the MC is started limitingfrom this period. In other words, the voltage transfer ratio of
the system is increased by the AC chopper. According to
Figure 8(a), it is confirmed that the input and q-axis current
are not drastically changed due to operation of the AC chopper.
Therefore, the proposed circuit can improve the output voltage
continuously. On the other hand, according to the deceleration
test shown Figure 8-(b), the IPM motor can be decelerated
without large current from the input and q-axis current.
Figure 9 shows the experiment operation waveforms of the
proposed circuit. Note that the proposed circuit operates the
IPM motor in case of load torque equal to 20%. In other words,
the mechanical power is equal to 720W. Additionally, thedamping resistor and the damping control are not applied in
the input filter and chopper. The resonant distortion in the
input filter is suppressed due to the loss of the chopper. For
this reason, the input current stability methods are applied inthis prototype. According to Figure 9, it is confirmed that thevoltage transfer ratio can be improved. The input current of
the experiment is more distorted than that of the simulation. In
the experimental, it is necessary to commutate the switching

Figure 8. Acceleration and deceleration test of the IPM motor.

Figure 9. Steady operation test.

pattern to prevent the source and the load from short circuit oropen circuit. As a result, the input current has distortions dueto the voltage error which is caused by the switchingcommutation. Besides, there are commutation failures in theswitching pattern because of the voltage detection error.
Figure 10 shows the total efficiency and the converter
efficiency characteristics of the system by using the proposed
circuit. It should be noted that the total efficiency is included
the conversion efficiency and the motor efficiency. In addition,the motor efficiency is calculated from the rotating speed andthe detected torque. As a result, it is confirmed that the total
efficiency and the converter efficiency at maximum point are
80.1% and 93.5% respectively.
Figure 11 shows the input and output current THD
characteristics based on the mechanical power of the IPM
motor. It is confirmed that the output current THD is less than
12 %. On the other hand, the input current THD is less than
10 %. The input current and output current THD becomespoor as the mechanical power decrease. This is because eventhe mechanical power reduces, although the harmonic
distortion of the input and output current amplitude is constant,the fundamental amplitude of the input and output current
becomes smaller.

Figure 13 is a simulation result shows the loss property.
Note that the rotating speed is 1.11pu and the mechanicalpower is 2kW. According to this result, the loss of the
proposed circuit is increased by the AC chopper. However,taken into consideration of the IPM motor loss, the loss of the
proposed circuit is less than that of the conventional MC. Thisis because the copper loss of the IPM motor, the conduction
loss of the Free Wheeling Diodes (FWD) and the conduction
loss of the IGBTs are increased due to field-weakening control
in the conventional MC.
Figure 14 shows the experimental efficiency comparison
between the proposed circuit and the conventional MC. The
torque is 12% and 20% in the experimental. However, thefield-weakening control in the IPM motor is not capable ofwide range of application. There, in order to extend the range
of application, the input voltage of the proposed circuit and theconventional MC are degraded. As a result, high rotating
speed of the IPM motor can be simulated. Accordingly, thetotal efficiency of the conventional MC which applied thefield-weakening control becomes low as the input voltage
decrease. This is because the conduction loss of the converter
and the primary order copper loss of the IPM motor are
increased to be larger due to the field-weakening control.
On the other hand, the AC chopper in the proposed circuit
can improve the input voltage which has been decreased. Thus,
the field-weakening control is not necessary to apply in the
proposed circuit. For this reason, high efficiency of the

THD (%)

B. Loss Analysis
Figure 12 is a simulation result shows the total efficiency
characteristics [7]. The number in the column () in this figure
shows the maximum voltage which is able to output by theconverter. Note that the filter loss and the iron loss are notconsidered in this graph. In addition, the mechanical power isconstantly equal to 2kW. The maximum efficiency of the
proposed circuit is 91.1% at 1.11pu rotating speed. Thus, theefficiency of the proposed circuit is higher by 12% comparing
with the conventional MC. The motor current in theconventional MC is increased due to the implementation of
the field-weakening control. On the other hand, the motor
current in the proposed circuit is not increased because thefield-weakening control is not applied in the matrix converter.
As a result, the efficiency of the proposed circuit is higher
than that of the conventional MC.

Figure 10. Efficiency characteristics of the proposed circuit.

Figure 11. THD characteristics.

Figure 12. Total efficiency characteristics by the simulation result.

proposed circuit can be achieved. According to Figure 14, theefficiency of the proposed circuit can be improved by 13% incase of the input voltage is equal to 140V in comparing withthe conventional MC. Therefore, high efficiency can beachieved without the field-weakening control and the validityof the simulation results are confirmed by experiment. Beside,
when the rotating speed of engine generator is slow which
results the supply voltage becomes low, the motor canefficiently to be driven, in order to implement the proposed
circuit without the field-weakening control.
V.

CONCLUSIONS AND FUTURE WORKThis paper discussed a circuit topology constructed from
the MC and the V-connection AC chopper. The advantages ofthe proposed circuit are following;The proposed circuit has the advantages of the origin
MC such as small size, light-weight and long life-time,even an AC chopper is added into the input side.

The MC and the V-connection chopper can becontrolled independently.

In this paper, the proposed circuit was modeled with a
3.7kW IPM motor in simulation and has proven theeffectiveness of the proposed control. The simulation results
confirmed that the proposed circuit could achieve a maximum
efficiency of 91.1%. Additionally, the efficiency is shown byimproving 12%. This is because the motor load current isincreased due to the field-weakening control. Field-weakening
control is applied at high rotating speed area that the converter
fails to deliver high output voltage.
The proposed circuit was tested experimental by using the
3.7kW IPM motor. In the acceleration test, it is confirmed thatthe input and q-axis current are not drastically changed due tooperation of the AC chopper. The proposed circuit achieves aunity input power factor and the voltage transfer ratio could be
improved by the boost-up operation. The input current THD
and output current THD are 7.5% and 3.53% respectively
when the mechanical power is equal to 720W. The
experimental results confirmed that the proposed circuit could
achieve a maximum converter efficiency and total efficiencyof 93.5 % and 80.1%, respectively. Therefore, thefundamental operation of the proposed circuit is confirmed by
the experimental results. It was confirmed that the efficiency
of system is affected by the field-weakening control in theexperimental, where the input voltage decreases and the fieldweakening control is implemented. As the result, the proposed
circuit could improve the efficiency of 13% in case of the
input voltage is equal to 140V in comparing with theconventional MC. Therefore, high efficiency of the drive
system for the IPM motor could be achieved without the fieldweakening control and the validity of the simulation results
were confirmed by experiment.
In future works, the validity of these simulation results will
be confirmed by using the IPM motor at the rated torque.
Besides, in term of the converter and motor loss, the proposed
circuit will compare with the BTB system.

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