IEEJ Journal of Industry ApplicationsVol.9 No.4 pp.428–434 DOI: 10.1541/ieejjia.9.428

Paper

Proposal for Universal Direct Converter Based on Matrix Converterfor Three-phase AC and DC Source

Daiki Yutaka∗ Student Member, Masato Koyama∗a)Member

Naoki Yamamura∗ Member, Muneaki Ishida∗∗ Fellow

(Manuscript received Oct. 28, 2019, revised Feb. 14, 2020)

Recently, power converters have been used in various electric machines, electric devices, etc. However, dependingon the power sources, it is necessary to change the circuit topology to DC/AC, AC/DC, or AC/AC. In some applicationssuch as the AC and DC dual locomotive, the power converter should be applicable for both AC and DC sources. Forthe applications, a converter that combines AC/DC and DC/AC is conventionally used. On the other hand, this paperpresents a direct converter that is applicable for any source, utilizing the topological common point between the three-level inverter and the matrix converter and developing a modulation method. By using the modulation method andthe matrix converter (MC) circuit, it is possible to achieve either DC/three-phase AC or three-phase AC/three-phaseAC power conversion with a common duty calculation scheme. In addition, the proposed system allows two features.First, a control of the neutral point fluctuation, and second, dead time compensation is not required because currentcommutation can be applied for the three-level DC/AC. The numerical simulations and experiments have validated theconversion and enabled the authors to propose a new concept for a power conversion system.

Keywords: matrix converter, three-level inverter, direct converter, universal power conversion

1. Introduction

Recently, energy saving technologies have attracted an at-tention from the viewpoint of global warming and energyshortage. In consequence, power converters have been morewidely used such as regenerative energies, EVs, and oth-ers. However, for each application, it is necessary to installa power converter corresponding to the kind of the powersource (DC/single-phase AC/three-phase AC). For example,there is an universal (AC-and-DC-dual) locomotive, an un-interruptible power supply and so on. Depending on theDC or AC source, the circuit topology should be changedto an inverter or a converter-inverter (1)–(3). Additionally, forthe single- or three-phase AC, the converter should have adifferent topology.

Because of the reasons, generally, the AC/AC converterconsists of a converter-inverter system called as an indirectpower converter. On the other hand, from 1980’s, a directpower converter has been studied, the converters are a cyclo-converter and a Matrix Converter (MC). The MC realizes di-rect conversion from AC to AC by switching of nine bidi-rectional switches and has no DC-link and a large capacitorfor an energy buffer. Since MC can improve the compactness,the life-time and the conversion efficiency of the indirect con-verter (4)–(8), it has gathered an attention.

Meanwhile, for the DC/AC conversion, there are some

a) Correspondence to: Masato Koyama. E-mail: koyama@ekc.mie-u.ac.jp∗ Mie University

1577, Kurimamachiya-cho, Tsu, Mie 514-8507, Japan∗∗ Chubu University

1200, Matsumoto-cho, Kasugai, Aichi 487-8501, Japan

three-level inverter topologies (9) (10). One of them is T-type what is composed of a two-level inverter containsbidirectional switches for the neutral-point voltage control.This circuit is realized by providing switches for the cur-rent paths of each phase on the source side and load side,as with the MC. Although the circuit topology is similar tothe MC, in the studies, the similarity has not been discussed.If each conversion can be realized by the identical topologywith changing the control function, it becomes a new powerconversion system for all power source types. In other word,by the system, replacing the circuits depending on the powersource types will be not necessary. Otherwise, in the studiesof the three-level inverter, the neutral-point voltage controlmethod has been discussed well to suppress the output dis-tortion caused by the neutral-point voltage fluctuation. Oneof the studies has introduced a feedback system for the volt-age control (11) (12).

This paper presents the new universal direct conversionsystem for three-phase AC or DC source using the MC topol-ogy. Even if the three-phase AC or the DC source is con-nected, the converter can output the modulated three-phasevoltage. In this paper, the control method is proposed basedon the Ishiguro, et al’s method (4) which is equivalent withVenturini’s method (5) introduced the virtual DC-link concept.Thanks to the virtual DC-link concept, it is possible to ap-ply the input current control by the switching. Utilizing thisfeature, for the DC or the three-phase AC, the three-level in-verter or the general MC operation can be conducted withthe identical MC topology, respectively. For the DC/AC, itcan operate the MC circuit as a three-level inverter by chang-ing the input current reference. When the three-level inverteroperation, the proposed system can control the neutral-point

c© 2020 The Institute of Electrical Engineers of Japan. 428

Proposal for Universal Direct Converter（Daiki Yutaka et al.）

voltage without any feedback controls since the averaged in-put current is controlled by the switching. On the other hand,in the MC, the switching methods that rectify currents whilepreventing short circuit and load release have proposed (13)–(15).By realizing the three-level inverter with the MC topology,the MC commutation method can be applied and prevent thesource short-circuit without the deadtime insertion.

Chapter 2 explains the topology of the proposed system.Next, Chapter 3 describes how to respond when the source ischanged with proposed modulation method. Then, the veri-fication result by simulation is shown in Chapter 4. Further-more, Section 5 shows the results of experiments using theproposed method on experimental machines. From these re-sults, it is validated that the proposed method can operate theMC circuit as the MC or the three-level inverter with onlychanging the reference. Section 6 examines the proposedmethod can perform the inverter and MC operation with theone completely identical circuit including the filters.

2. Universal Direct Converter

2.1 Topology of Universal Direct Converter Thetopology of the universal direct converter is illustrated inFig. 1. The topology for connecting a three-phase AC sourceor a DC source are shown in Figs. 1(a) and (b), respectively.The (a) and (b) are operated as the general MC and a three-level inverter what is similar to the T-type three-level inverter,respectively. Since the main purpose of this paper is to verifythe basic switching operation using the identical main circuit,the input filters are conformed to the conventional MC andthree-level inverter, respectively. In the future, using the cir-cuit that all part is identical, it is reported about the validationof the proposed method.

(a) Three-phase AC source connection.

(b) DC source connection.

Fig. 1. The topology of the universal direct converter in this paper

2.2 Commutation Sequence The main circuit con-sists of nine bidirectional switches that are anti-parallelIGBTs with freewheeling diodes. To avoid the short-circuit inthe input side and open-circuit in the output side, the switch-ing of the IGBTs are performed with the commutation se-quence (13). In this paper, the current commutation is applied,and the sequence is designed with each output phase-currentdirection.

3. Modulation Method of the Proposed System

The proposed system refers the conventional modulationmethod (4). For the MC control, there are several meth-ods which are Venturini’s (5), virtual indirect (6), direct space-vector (7), and other modulations. In them, the method (4) canbe regard as Venturini’s modulation introduced the virtualDC-link. Hence, based on three- to two-phase voltage con-version of the input and output side, the method can generatethe duty signal for MC. In this paper, for the three-phase ACsource and the MC operation, the modulation is given from (4).On the other hand, for the DC source and the three-level in-verter operation, this paper proposes changing the referenceof the input side.3.1 The Duty Ratio of Each Switch The duty ratio

of the switch S xy in the Fig. 1 is defined as

dxy =(ON time of S xy)

Ts· · · · · · · · · · · · · · · · · · · · · · · · · (1)

x ∈ {u, v,w}, y ∈ {r, s, t}where Ts is the carrier period.

Here, let us show the constraint conditions of the duty.⎧⎪⎪⎪⎨⎪⎪⎪⎩

dur + dus + dut = 1dvr + dvs + dvt = 1dwr + dws + dwt = 1

· · · · · · · · · · · · · · · · · · · · · · · · · · · · (2)

which means the total ON-time should be Ts.The averaged output phase-voltage v̄x in Ts is given by⎡⎢⎢⎢⎢⎢⎢⎢⎣v̄u

v̄v

v̄w

⎤⎥⎥⎥⎥⎥⎥⎥⎦ =⎡⎢⎢⎢⎢⎢⎢⎢⎣dur dus dut

dvr dvs dvt

dwr dws dwt

⎤⎥⎥⎥⎥⎥⎥⎥⎦

⎡⎢⎢⎢⎢⎢⎢⎢⎣vr

vs

vt

⎤⎥⎥⎥⎥⎥⎥⎥⎦ · · · · · · · · · · · · · · · · · · · · · · (3)

where vy is the input phase-voltage to the MC.3.2 Basic Concept of the Modulation The proposed

system uses the virtual DC-link from the input-side space-vector, it means the dq-axis voltage of the input (4). From thed- or q-axis of the input voltage, the virtual DC-link voltageEconst is derived, and the conversion from this voltage to theoutput voltage can be derived as follows:

Econst =[X1 X2 X3

]⎡⎢⎢⎢⎢⎢⎢⎢⎣vr

vs

vt

⎤⎥⎥⎥⎥⎥⎥⎥⎦ · · · · · · · · · · · · · · · · · · · · · (4)

⎡⎢⎢⎢⎢⎢⎢⎢⎣v̄u

v̄v

v̄w

⎤⎥⎥⎥⎥⎥⎥⎥⎦ = A

⎡⎢⎢⎢⎢⎢⎢⎢⎣Y1

Y2

Y3

⎤⎥⎥⎥⎥⎥⎥⎥⎦ Econst · · · · · · · · · · · · · · · · · · · · · · · · · · · · · (5)

where A is the amplitude modulation rate. The X function inEq. (4) is the conversion vector for the d- or q-axis, the axisis decided to get the in-phase component of the input volt-age vector. The Y function in Eq. (5) is the normalized outputphase-voltage command.

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Proposal for Universal Direct Converter（Daiki Yutaka et al.）

In the case of changing the source between AC to DC, onthe Eq. (4), it can be dealt as that the conversion vector forgetting the in-phase component should be changed. For thethree-phase AC and the DC source, the output voltage is de-rived in next subsections, respectively.3.3 Connecting Three-phase AC Source (4) In the

case of the three-phase AC source is connected, the sourcephase-voltage (vri, vsi and vti) and the input phase-voltage (vr,vs and vt) can be written as follows:⎡⎢⎢⎢⎢⎢⎢⎢⎣vri

vsi

vti

⎤⎥⎥⎥⎥⎥⎥⎥⎦ = Vi

⎡⎢⎢⎢⎢⎢⎢⎢⎣cos(ωit)

cos(ωit − 2π/3)cos(ωit + 2π/3)

⎤⎥⎥⎥⎥⎥⎥⎥⎦ · · · · · · · · · · · · · · · · · · · · · (6)

⎡⎢⎢⎢⎢⎢⎢⎢⎣vr

vs

vt

⎤⎥⎥⎥⎥⎥⎥⎥⎦ = V

⎡⎢⎢⎢⎢⎢⎢⎢⎣cos(ωit − δ)

cos(ωit − δ − 2π/3)cos(ωit − δ + 2π/3)

⎤⎥⎥⎥⎥⎥⎥⎥⎦ · · · · · · · · · · · · · · · · · · (7)

where Vi is the source phase-voltage amplitude, V is the MCinput phase-voltage amplitude, ωi is the source voltage angu-lar frequency and δ is the lag caused by the input filter.

The X function for getting the virtual DC-link voltage isexpressed by

⎡⎢⎢⎢⎢⎢⎢⎢⎣X1

X2

X3

⎤⎥⎥⎥⎥⎥⎥⎥⎦ =⎡⎢⎢⎢⎢⎢⎢⎢⎣

cos(ωit + ϕi)cos(ωit + ϕi − 2π/3)cos(ωit + ϕi + 2π/3)

⎤⎥⎥⎥⎥⎥⎥⎥⎦ · · · · · · · · · · · · · · · · · · · · (8)

where ϕi is the input-current lag reference.The Y function due to make the output voltage a symmet-

rical three-phase AC is given by

⎡⎢⎢⎢⎢⎢⎢⎢⎣Y1

Y2

Y3

⎤⎥⎥⎥⎥⎥⎥⎥⎦ =⎡⎢⎢⎢⎢⎢⎢⎢⎣

cos(ωot + ϕo)cos(ωot + ϕo − 2π/3)cos(ωot + ϕo + 2π/3)

⎤⎥⎥⎥⎥⎥⎥⎥⎦ · · · · · · · · · · · · · · · · · · · (9)

where is ωo is the output voltage angular frequency and ϕo isthe output-voltage phase lag reference.

Substituting Eq. (4) into (5), the duty ratio are given as fol-lows:⎡⎢⎢⎢⎢⎢⎢⎢⎣dur dus dut

dvr dvs dvt

dwr dws dwt

⎤⎥⎥⎥⎥⎥⎥⎥⎦ = A

⎡⎢⎢⎢⎢⎢⎢⎢⎣Y1

Y2

Y3

⎤⎥⎥⎥⎥⎥⎥⎥⎦[X1 X2 X3

]· · · · · · · · (10)

However, the constraint of Eq. (2) is not satisfied since thesum of three-phase voltage is zero. Thus, introducing the hfunction (zero phase component), it can be rewritten as a fol-low:⎡⎢⎢⎢⎢⎢⎢⎢⎣dur dus dut

dvr dvs dvt

dwr dws dwt

⎤⎥⎥⎥⎥⎥⎥⎥⎦=A

⎡⎢⎢⎢⎢⎢⎢⎢⎣Y1

Y2

Y3

⎤⎥⎥⎥⎥⎥⎥⎥⎦[X1 X2 X3

]+

⎡⎢⎢⎢⎢⎢⎢⎢⎣hr hs ht

hr hs ht

hr hs ht

⎤⎥⎥⎥⎥⎥⎥⎥⎦

· · · · · · · · · · · · · · · · · · · (11)

hr + hs + ht = 1 · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · (12)

The h function has various cases that satisfy the aboveEq. (12). Even though the maximum voltage-utility-rate ofMC can be up to 0.866 by the special h in Ref. (4), in this pa-per, the h function is defined as a follow to set the zero-phasevoltage is zero[V].

hr = hs = ht =13· · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · (13)

From Eq. (11), the proposed system can output the mod-ulated three-phase AC. To convert the duty ratio given byEq. (11) to the switching pulse, a PWM algorithm for MCproposed in (4) is used. In the algorithm, using a sum of theduties at each output-phase, it can easily modulate the dutyto the pulse. About more details of this PWM, please referto (4). Then, for the simulations and experiments in this pa-per, the carrier signal is a triangular wave that the frequencyis 10 kHz.3.4 Connecting DC Supply When the sources is DC

and let us assume the input side filter consists of only capac-itors to simplify the calculation, the capacitor phase voltage(vr, vs and vt) of the input filter is expressed by⎡⎢⎢⎢⎢⎢⎢⎢⎣vr

vs

vt

⎤⎥⎥⎥⎥⎥⎥⎥⎦ =⎡⎢⎢⎢⎢⎢⎢⎢⎣

E/20−E/2

⎤⎥⎥⎥⎥⎥⎥⎥⎦ · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · (14)

where E is the DC voltage.In the three-level inverter, the neutral point voltage vs is

not fixed due to that the fluctuation is depending on the phasecurrent flow. Hence, if any controls are not applied, the out-put voltage will be distorted. For this reason, it is importantto control the neutral point voltage. In this system, it is con-trolled by setting the X function that is not only the transformfunction to get the in-phase component of the input voltage,but also the input phase-current command. Thanks to thisfunction, the neutral point current is kept at zero[A]. There-fore, the X function is given by⎡⎢⎢⎢⎢⎢⎢⎢⎣X1

X2

X3

⎤⎥⎥⎥⎥⎥⎥⎥⎦ =⎡⎢⎢⎢⎢⎢⎢⎢⎣

10−1

⎤⎥⎥⎥⎥⎥⎥⎥⎦ . · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · (15)

The Y function is set as same as Eq. (9). Similarly, the dutyratio and the h function are defined as Eqs. (11) and (13), re-spectively. Then, the three-level inverter operation is con-ducted.

Due to that, this paper has proposed the control system foroperating both of the three-phase AC to AC and the DC to ACconversion. As described above, since the identical main cir-cuit and the modulation method with the MC, the MC com-mutation method can be used for the three-level inverter op-eration.

4. Numerical Simulations

In this simulation, the account of the proposed control sys-tem is verified. The universal direct converter is simulatedby Myway plus, PSIM, version 11.1.3. Note that, the carrierwave is the triangular wave, and the commutation method isthe current commutation.4.1 Connecting Three-phase AC Source In this sub-

section, the three-phase AC source is connected. The simu-lation parameters in Fig. 1(a) are listed in Table 1. In orderto set the input power factor to 1, the input-current lag ref-erence ϕi is given as zero[deg]. In addition, since simulatingthe voltage drop of IGBTs and diodes, the datasheet of eachelement is referred and a series-resistor 1.6Ω is inserted toeach switch to emulate the drop. The results of the simula-tion is shown as Fig. 2. Figure 2(a) is the input line to linevoltage (vrs, vst, vtr), (b) is the input current, (c) is the outputline-to-line voltage, (d) is the output current, (e) and (f) are

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Table 1. Simulation parameters when connecting three-phase AC supply

Fig. 2. Simulation results (three-phase AC supply)

Fig. 3. FFT analysis of the simulated output current(three-phase AC supply)

the voltage across and the current through S ru. From (b), theharmonics of the MC input current are removed by the inputfilter on the source current. It can be seen from (c) that aPWM waveform is generated in the output line-to-line volt-age. The three-phase AC output is confirmed from the outputcurrent of (d). From (e) and (f), the voltage and current at theswitch don’t have surges, over-voltages, and -currents. Al-though this paper only shows the S ru, other switches havesimilar responses. Hence, in the numerical simulation, theproposed system can correctly perform the conversion. Fur-thermore, Fig. 3 shows the FFT analysis result of the outputcurrent. From this result, it can confirm the output currentwith the command frequency.4.2 Connecting DC Supply The simulation parame-

ters for Fig. 1(b) are listed in Table 2. In order to set the inputpower factor to 1, the input-current lag reference is given aszero[deg]. As the same manner with the previous subsec-tion, to emulate the drop voltage, the equivalent resistor is

Table 2. Simulation parameters when connecting DC supply

Fig. 4. Simulation Results (DC supply)

Fig. 5. FFT analysis of the simulated output current(DC supply)

inserted. Figure 4(a) is the input line-to-line voltage, (b) isthe raw and filtered input current from the neutral-point thatthe cutoff frequency is 500 Hz to remove the switching com-ponent, (c) is the output line-to-line voltage, (d) is the outputphase-current, (e) is the switch voltage, and (f) is the switchcurrent of S ur.

From (b), the filtered neutral-point current is kept atzero[A]. Hence, in (a), the input line-to-line voltage is main-tained. It can be seen from (c) that a PWM waveform isgenerated in the output line-to-line voltage. Thanks to thismaintaining, three-phase AC is obtained as shown in (d). Forthe frequency component analysis, Fig. 5 shows the FFT re-sult of the output current in Fig. 4(d). From this, it can con-firm that the output has only the command frequency com-ponent. From (e) and (f), similarly with the Figs. 2(e)(f), theswitch does not have a surge, over-voltage, and over-currentresponse. Consequently, it can confirm that the proposed uni-versal direct converter conducts the inverter (DC/AC) opera-tion without any over-voltage and -current.

From this result, using the MC topology, both the

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Fig. 6. Comparison of the output current in the three-level inverter mode, where [A], [B], and [C] are under theideal switching, switching with the dead-time, and withthe commutation, respectively

three-phase AC/AC and the three level DC/AC conversioncan be achieved. Here, to confirm the account of using thecommutation when the three-level inverter operation, the u-phase output current under the following three conditions iscompared with the simulation.[A] No short circuit prevention measures[B] Dead time applied w/o any voltage compensation[C] Commutation applied w/o any voltage compensation

Figure 6 shows the comparison of the u-phase output cur-rent under each condition. The dead time and the commu-tation time are 2 [μs]. Since the commutation can avoidthe current-path is lost, the load is always connected to thesource. On the other hand, with the deadtime, generally, theswitching time is only considered and the current-path is notkept. Hence, using the proposed system and the commuta-tion which is developed for the MC, the voltage error in thethree-level inverter can be suppressed.

Next, for validating the simulation results, the experimentis mentioned by using the product.

5. Experimental Results

In order to validate the numerical simulation, using an ex-perimental setup consists of MC circuit, PE-Expert3 (DSPand FPGA) (Myway Plus), the experiment under same con-dition with the simulations is conducted. Figure 7 shows theexperimental machine.5.1 Connecting Three-phase AC Source In the ex-

periment, the parameters are shown in Table 1.Figure 8 shows the experimental result with connecting

three-phase AC source: (a) is the input line-to-line voltage.(b) is the output current. Furthermore, Fig. 9 shows the FFTanalysis result of the output current. From these results, aswith the simulation, it can confirm the three-phase AC/ACconversion is achieved.5.2 Connecting DC Source In the case of the DC

source, the parameters are given from Table 2.Figures 10(a) and (b) show the input line-to-line voltage.

the output current, respectively. Furthermore, Fig. 11 showsthe FFT result of the output current. From these results, it canconfirm that the output current is controlled at the commandfrequency. Besides, the neutral-point voltage is maintainedas same as the simulation.

The aforementioned experimental results are in good

Fig. 7. Experimental setup (Myway Plus, PE-Expert3 and MC)

Fig. 8. Experimental Results (three-phase supply)

Fig. 9. FFT analysis of the experimental output current(three-phase supply)

Fig. 10. Experimental Results (DC supply)

Fig. 11. FFT analysis of the experimental output current(DC supply)

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Fig. 12. The topology for the DC source using the iden-tical input-filter with the circuit for the three-phase ACsource

Table 3. Simulation parameters using the identicalinput-filter with the circuit for the three-phase AC source

agreement with the simulation results, and the validity of theexperimental results can be confirmed.

6. Verification When using the Identical Filter asMC

In this section, using the whole identical circuit includingthe filter part, it examines the proposed method can performthe inverter and MC operation with the one circuit.6.1 The Topology with the Same Filter Figure 12

shows the topology using a DC source. Unlike Fig. 1(b), theinput filter of Fig. 12 is identical with the circuit of Fig. 1(a)un-connects to the s-phase.6.2 Numerical Simulations The simulation parame-

ters for Fig. 12 are shown in Table 3. In order to set the inputpower factor to 1, the input-current lag reference ϕi is givenas zero[deg]. In addition, for considering the voltage dropof IGBTs and diodes, the series-resistor 1.6Ω is inserted toeach switch to emulate the voltage drop referred from thedatasheet of each element. Figure 13(a) is the input line-to-line voltage, (b) is the raw and filtered input current from theneutral-point that the cutoff frequency is 500 Hz to removethe switching component, (c) is the output line-to-line volt-age, (d) is the output phase-current, (e) is the switch voltage,and (f) is the switch current of S ru. From (b), the filteredneutral-point current is kept at zero[A]. Hence, in (a), the in-put line-to-line voltage is maintained. It can be seen from(c) that a PWM waveform is generated in the output line-to-line voltage. Thanks to this maintaining, three-phase AC isobtained as shown in (d). For the frequency component anal-ysis, Fig. 14 shows the FFT result of the output current inFig. 13(d). From this, it can confirm that the output has onlythe command frequency component. From (e) and (f), it canbe confirmed that no surge has occurred in the switch.

Fig. 13. The simulation result of applying the DCsource with the identical filter

Fig. 14. FFT analysis of the simulated output current(applying the DC source with the identical filter)

Fig. 15. Experimental Results (applying the DC sourcewith the identical filter)

Fig. 16. FFT analysis of the experimental output current(applying the DC source with the identical filter)

From these results, in the simulation using the completelyidentical circuit, the proposed system can perform the in-verter operation as same as Fig. 4.6.3 Experimental Results In the experiment, the pa-

rameters are set from Table 3. Figures 15(a) and (b) showthe input line-to-line voltage, the output current, respectively.Furthermore, Fig. 16 shows the FFT result of the output cur-rent. From these results, it can confirm that the output current

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Proposal for Universal Direct Converter（Daiki Yutaka et al.）

is controlled at the command frequency.The aforementioned experimental results are in good

agreement with the simulation results, and the validity ofthe experimental results can be confirmed. Therefore, fromthese numerical simulations and experimental results, withthe three-phase AC and DC source, this paper established theproposed system can realize the inverter and MC operationusing the one completely identical converter circuit.

7. Conclusions

This paper has proposed the power converter that can han-dle both three-phase AC/AC and three-level DC/AC conver-sion using the identical main circuit and the control methodbased on Ref. (4). Furthermore, it was found that there isthe following significance by the proposed method when con-necting DC power.• Capacitor neutral point potential fluctuation can be con-

trolled by the input side transform vector X.• The commutation sequence developed for MC can re-

duce the output voltage error compared to using the deadtime, thanks to the proposed system can apply the com-mutation.

From the simulations and experiments, the features of theproposed universal direct converter are validated. Addition-ally, it showed the simulation and experiment using the com-pletely identical circuit including the filter part. From theseresults, this paper can establish the realization of the univer-sal direct converter.

As one of future works, for introducing a single-phase ACsource to the proposed system, the authors will work about apower pulsation compensation for the proposed system.

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Daiki Yutaka (Student Member) received the B.E. degree in electricand electrical engineering from Mie University, Mie,Japan, in 2018, where he is currently working towardthe M.E. degree. His research interests include powerelectronics.

Masato Koyama (Member) received the B.E. degree in electricand electrical engineering from National Institute ofTechnology, Kisarazu College, Kisarazu, Japan, in2012, and M.E., and Ph.D. degrees in electrical andcomputer engineering from Yokohama National Uni-versity, Yokohama, Japan, in 2014 and 2017, respec-tively. Since 2017, he has been with the Faculty ofEngineering, Mie University, where he is currently anAssistant professor. His research interests includesactuators, power electronics, motor drives, and mo-

tion control. Dr. Koyama is a member of IEEJ, IEEE, SICE, and RSJ.

Naoki Yamamura (Member) received the B.S. degree and M.S. de-gree from Nagoya Institute of Technology in 1989and 1991, respectively, both in Electrical Engineer-ing. He received the Dr.Eng. degree from Nagoya In-stitute of Technology in 1993. Since 1993, he hasbeen associated with the Department of ElectricalIntelligence Engineering, Nagoya Institute of Tech-nology, where he was an Assistant Researcher from1993. Since 1998, he has been associated with theDepartment of Electrical and Electronic Eng. Mie

University, as an Assistant Professor. He was promoted to associate pro-fessor in 2008. His present research is development of power conversionsystem using natural energy, and matrix converter system. Dr. Yamamura isa member of the IEEE, JIPE and IEE of Japan.

Muneaki Ishida (Fellow) received the B.S., M.S. and Dr.Eng. De-grees in Electrical and Electronic Engineering fromNagoya University in 1975, 1977 and 1980, respec-tively. From 1980 to 1987, he was with the Dept. ofElectrical and Electronic Eng., Nagoya University asan Assistant Professor. From 1987 to 2018, he waswith the Dept. of Electrical and Electronic Eng., MieUniversity, as an Associated Professor (1987–1996)and a Professor (1996–2018). Since 2018, he hasbeen with the Dept. of the Astronautics and Aero-

nautics in Chubu University as a Professor. His research interests includeelectrical actuator drives, power converters, etc. Dr. Ishida is a member ofJSASS, JSME, IEEE, IEEJ and SICE.

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