Model Predictive Control of Bidirectional AC-DC Converter for Energy Storage System

Transcription

1 J Elect Eng Technol.015;10(1): ISSN(Pint) ISSN(Online) Model Pedictive Contol of Bidiectional AC-DC Convete fo Enegy Stoage System Md. Pavez Akte*, Saad Mekhilef, Nadia Mei Lin Tan** and Hiofumi Akagi*** Abstact Enegy stoage system has been widely applied in powe distibution sectos as well as in enewable enegy souces to ensue uninteuptible powe supply. This pape pesents a model pedictive algoithm to contol a bidiectional AC-DC convete, which is used in an enegy stoage system fo powe tansfeing between the thee-phase AC voltage supply and enegy stoage devices. This model pedictive contol (MPC) algoithm utilizes the discete behavio of the convete and pedicts the futue vaiables of the system by defining cost functions fo all possible switching states. Subsequently, the switching state that coesponds to the minimum cost function is selected fo the next sampling peiod fo fiing the switches of the AC-DC convete. The poposed model pedictive contol scheme of the AC-DC convete allows bidiectional powe flow with instantaneous mode change capability and fast dynamic esponse. The pefomance of the MPC contolled bidiectional AC-DC convete is simulated with MATLAB/Simulink and futhe veified with 3.0kW expeimental pototypes. Both the simulation and expeimental esults show that, the AC-DC convete is opeated with unity powe facto, acceptable THD (3.3% duing ectifie mode and 3.5% duing invete mode) level of AC cuent and vey low DC voltage ipple. Moeove, an efficiency compaison is pefomed between the poposed MPC and conventional VOC-based PWM contolle of the bidiectional AC-DC convete which ensues the effectiveness of MPC contolle. Keywods: Model pedictive contol (MPC), Bidiectional AC-DC convete, Unity powe facto, Reactive powe, Enegy stoage system 1. Intoduction Renewable enegy souces ae playing an indispensable ole to satisfying the futue enegy demand. The powe povided by enewable enegy souces is inteuptible and unpedictable because these enegy souces depend on the weathe conditions [1]. Hence, an enegy stoage system is necessay to use in enewable enegy souces to povide a eliable powe supply and make it dispatch-able on demand [-4]. Fig. 1 shows an enegy stoage system which composes of a Li-ion battey bank, a bidiectional isolated DC-DC convete and a thee-phase bidiectional AC-DC convete [5]. The thee-phase bidiectional AC-DC convete is an essential pat of the enegy stoage system due to its bidiectional-powe-flow and synchonization capabilities [6]. This bidiectional AC-DC convete should to be highly efficient as it needs to pevent the poblems of poo Coesponding Autho: Powe Electonics And Renewable Enegy Reseach Laboatoy (PEARL), Dept. of Electical Engineeing, Univesity of Malaya, Kuala Lumpu, Malaysia. (saad@um.edu.my) * Powe Electonics And Renewable Enegy Reseach Laboatoy (PEARL), Dept. of Electical Engineeing, Univesity of Malaya, Kuala Lumpu, Malaysia. (pavez06005@gmail.com) ** Dept. of Electical Powe Engineeing, Univesiti Tenaga Nasional, Kajang, Malaysia. (nadia@uniten.edu.my) *** Dept. of Electical and Electonic Engineeing, Tokyo Institute of Technology, Tokyo, Japan. (akagi@ee.titech.ac.jp) Received: June 1, 014; Accepted: August 13, 014 powe quality such as high total hamonic distotion (THD), low powe facto, ac voltage distotion, ipple in DC cuent and DC voltage pulsations [7-9]. Theefoe, seveal topologies and contol methods have been investigated to impove the efficiency and pefomance of this bidiectional AC-DC convete. The classical contol of AC-DC convete is geneally based on voltage-oiented contol (VOC) scheme, which decomposes the active and eactive powe in stationay α-β coodinate and synchonize the powes with otating d-q efeence fames by chaacteizing the cuent contol loops using PI contolles [10]. Moeove, a vitual-flux-oiented contol has been poposed in [11], which also uses the PI contolles. The majo limitation of these contol schemes is tuning the PI contolles which futhe affect the coodinate tansfom accuacy. Futhemoe, diect powe contol (DPC) scheme [1, 13] has been applied fo gid-tied AC-DC convete based on diect toque contol (DTC) [14, 15] pinciple, which also uses the PI contolles. In ode to impove the pefomance of the convete, look-up table (LUT) based diect powe contol (DPC) scheme has been poposed in [16] and [17], in which the switching action of the convete is done with pedefined switching state table on the basis of active and eactive powe chaacteistics. This look-up table based DPC method has vaiable switching poblem, which poduces undesiable hamonic spectums. To ovecome this vaiable Copyight c The Koean Institute of Electical Enginees This is an Open-Access aticle distibuted unde the tems of the Ceative Commons Attibution Non-Commecial License ( licenses/by-nc/3.0/)which pemits unesticted non-commecial use, distibution, and epoduction in any medium, povided the oiginal wok is popely cited. 165

2 Model Pedictive Contol of Bidiectional AC-DC Convete fo Enegy Stoage System Fig. 1. An enegy stoage system [5] switching, a fuzzy-logic based switching state selection citeia has been pesented in [18] by avoiding pedefined switching table. Although the active and eactive powe ae smoothed in fuzzy-logic based DPC algoithm compaed with classical DPC, but its sampling fequency is little bit high. Theefoe, a sliding mode nonlinea contol appoach has been investigated in [19] fo active and eactive powe egulation of gid connected DC-AC convete, which is vey much dependent on vaiables. The pinciple featue of the model pedictive contol (MPC) scheme is to pedict the futue behavio of the contol vaiables. This MPC algoithm has become an attactive mode of contol technique fo bidiectional AC- DC convete compaing with all the classical solutions due to its simple and intuitive concept with fast dynamic esponses [0-]. Moeove, MPC algoithm is vey easy to configue with constaints and non-lineaity and also fo pactical implementation. The fast and poweful micopocessos ae available today to implement the pedictive contol algoithm vey easily as it equies highe numbe of calculations compaed with all the classical contols [6, 0]. Till to date, this algoithm is poposed fo an active font-end ectifie [3-5], indiect matix convete [6-8] and voltage souce invete []. Although model pedictive algoithm is an attactive altenative fo contolling the powe convetes, it has been used vey limitedly to contol powe flow of a bidiectional AC-DC convete. This pape poposes a model pedictive contol (MPC) algoithm that is applied in a bidiectional AC-DC convete fo enegy stoage system. The system configuation and woking pinciple of the bidiectional AC-DC convete ae elaboately descibed in section. The fomulation of MPC method with discete time model, the cost function used fo selection of switching states and a detailed explanation of contol scheme and algoithm ae in section 3. The pefomance of the poposed MPC method fo bidiectional AC-DC convete is tested with MATLAB/Simulink and the simulation esults ae pesented in section 4. The simulation esults ae futhe veified with a 3.0 kw expeimental configuation, which ae discussed in section 5. Section 6 descibes the efficiency compaison between the poposed MPC and conventional VOC-based PWM contolle of the bidiectional AC-DC convete. Finally section 7 daws the conclusion of the poposed MPC contolled bidiectional AC-DC convete fo enegy stoage system.. Bidiectional AC-DC Convete Topology.1 System configuation Fig. shows the thee-phase bidiectional AC-DC convete topology which tansfes powe between the thee-phase AC voltage supply and the DC voltage bus. The bidiectional AC-DC convete consists of six IGBT- Diode switches (S 1 -S 6 ), which is connected with theephase AC voltage supply though seies filte inductance (L s ) and esistance (R s ). A DC capacito (C dc ) is connected acoss DC voltage bus to keep the voltage (V dc ) constant. The bidiectional AC-DC convete opeates in two modes. The fist mode is ectifie mode, in which the bidiectional AC-DC convete opeates as a font end ectifie and allows powe tansfe fom the thee-phase AC voltage end to the DC voltage bus. The second mode is invete mode, whee the powe flows fom DC voltage bus to thee-phase AC voltage end and the convete acts as a voltage souce invete. n Thee Phase AC Voltage v sa v sb v sc i sa i sb i sc R s R s R s L s L s L s S 1 S 3 S 5 S v ao S 4 S 6 DC Voltage Bus Fig.. Thee-phase bidiectional AC-DC convete topology v bo v co C dc I dc o V dc 166 J Elect Eng Technol.015;10(1):

3 Md. Pavez Akte, Saad Mekhilef, Nadia Mei Lin Tan and Hiofumi Akagi. Woking pinciple Model pedictive contol (MPC) algoithm is applied to contol the powe flow of the thee-phase bidiectional AC- DC convete. The woking pinciple of MPC scheme is based on a finite numbe of possible switching states, which utilizes the discete behavio of a static powe convete. In the case of thee-phase bidiectional AC- DC convete, MPC algoithm utilizes the discete natue of filte inductances (L s ) to contol the powe flow by appopiate switching action. In ode to select the appopiate switching state to be applied fo fiing the convete switch, a selection citeion must be defined with a cost function which measues the eo between efeences and pedicted values. Then, the state that minimizes the cost function is selected fo the next sampling inteval. In ode to avoid shot cicuit, the two switches in each leg of the bidiectional AC-DC convete should be opeated in a complementay mode. Hence, the gating signals S a, S b and S c detemine the switching states of the thee-phase bidiectional AC-DC convete as follows: ïì 1, S 1 is on and S is off S a = í ïî 0, S 1 is off and S is on (1) ïì 1, S 3 is on and S 4 is off S b = í ïî 0, S 3 is off and S 4 is on () ïì 1, S5 is on and S 6 is off S c = í ïî 0, S5 is off and S6 is on (3) Theefoe, the switching function vecto ( S ) of the bidiectional AC-DC convete can be expessed as, S = ( S a + w S S c ) 3 b + w (4) whee, jp / 3 w = e, is the unity vecto. The output voltage space vecto ( v conv ) of the AC-DC convete fo both the ectifie and invete mode can be pesented with phase to neutal voltages (v ao, v bo and v co ) as, vconv = ( vao + w v bo + w vco 3 ). (5) This output voltage space vecto ( v conv ) can also be elated to the DC bus voltage (V dc ) and the switching function vecto ( S ) as, v conv = S V. (6) dc Thee ae eight possible voltage vectos can be obtained fom the eight consequence switching states of the switching signals S a, S b and S c. These eight voltage space Table 1. Voltage space vectos of the bidiectional AC-DC convete vectos ae listed in Table 1. The enegy stoage system allows bidiectional powe tansfe between thee-phase AC voltage side and enegy stoage device though the bidiectional AC-DC convete. Hence, the bidiectional AC-DC convete needs to be opeated in two modes, which ae specified as ectifie mode and invete mode. The opeating pinciple of the bidiectional AC-DC convete fo both the ectifie and invete modes ae elaboately descibed in the following subsection...1 Rectifie and invete modes of opeation Duing the ectifie mode of opeation, the bidiectional AC-DC convete acts as a font end ectifie that is connected to the thee-phase AC voltage souce though the input filte inductance L s and esistance R s as shown in Fig.. By applying Kichhoff s voltage law at the ac side of the ectifie, the elationship between the thee-phase AC voltage and ectifie input voltage vectos ae, dis æ ö vs = Ls + Rsis + çvao + wv bo + w vco dt 3 è ø æ ö - çvno + wvno + w vno. 3 è ø The space-vecto model of thee-phase AC voltage v s and cuent i s can be deived fom phase voltage and cuent as, and Switching states Voltage space vecto S a S b S c v conv v 1 = v = -( 1/ 3) V dc - j( 3 / 3) V dc v 3 = -( 1/ 3) V dc + j( 3 / 3) V dc v 4 = -( / 3) V dc v 5 = ( / 3) V dc v 6 = ( 1/ 3) V dc - j( 3 / 3) V dc v 7 = ( 1/ 3) V dc + j( 3 / 3) V dc v 8 = 0 vs = ( vsa + w v sb + w vsc 3 ) (7) (8) is = ( isa + w i sb + w isc), (9) 3 whee v sa, v sb, and v sc ae phase voltages; i sa, i sb, and i sc ae phase cuents of thee-phase AC voltage souce duing the 167

4 Model Pedictive Contol of Bidiectional AC-DC Convete fo Enegy Stoage System ectifie mode. The input cuent dynamics of the bidiectional AC-DC convete duing ectifie mode opeation can be evaluated fom (5) and (7) as, dis 1 = ( vs - vconv - Rsis ) (10) dt Ls The bidiectional AC-DC convete woks as a voltage souce invete duing the invete mode, which allows the powe tansfe fom the DC voltage bus to the thee-phase AC voltage end. Theefoe, the load cuent dynamics of the convete emains same as in (10). Howeve, it is 180 o out-of-phase with espect to the load voltage. 3. MPC Fomulation The fomulation of model pedictive contol (MPC) algoithm fo thee-phase bidiectional AC-DC convete is descibed in the following section. The MPC contolle is fomulated in discete time domain. Theefoe, it is necessay to tansfom the dynamic system of bidiectional AC-DC convete fo both ectifie and invete mode of opeation epesented in (10) into discete time model at a specific sampling time T s. 3.1 Discete time model fo pediction hoizon A discete time model is used to pedict the futue values of cuents and voltages in the next sampling inteval (k+1), fom the measued cuents and voltages at the k th sampling instant. The system model deivative dx / dt fom Eule appoximation can be expessed as: x( k) dx x -» (11) dt T s algoithm is to minimize the eo with fast dynamic esponse between the pedicted and efeence values of the discete vaiables. To achieve this objective, an appopiate cost function (e) is defined with a measuement of pedicted input eo. Hence, the cost function fo the ectifie and invete can be expessed with the absolute eo between the pedictive and efeence values of input and load cuent fo both the ectifie and invete mode of opeation as, e = i ef - ip (13) whee, e is the cost function. The efeence input and pedicted cuent ae i ef_ec and i p_ec, and i ef_inv and i p_inv fo the ectifie and invete modes, espectively. 3.3 Contol scheme Fig. 3 shows the poposed contol stategy of model pedictive contol (MPC) algoithm. At fist, the opeating mode of the bidiectional AC-DC convete is selected depending on chaging state of the enegy stoage device, which is detemined by the DC bus voltage V dc. If the chaging state (detemined by DC voltage) is less than theshold level, then it is opeated in ectifie mode, othewise it is opeated in invete mode. Duing the ectifie mode of opeation, thee-phase input AC cuent is ( k) is measued and the futue value of this cuent is is pedicted by using the discete time Eq. (1) fo each one of eight possible switching vecto ( S ) of Using the above appoximation, the discete time model of pedictive cuents and voltages fo the next (k+1) sampling instant of the bidiectional AC-DC convete in ectifie and invete mode can be deived. The discete time model of pedictive input cuents at the next sampling instant (k+1) fo the ectifie and invete mode of the bidiectional AC-DC convete can be evaluated fom (10) with the help of Eule appoximation as, v s i s i s Sa Sb Sc is æ ö + R T ç s L è s ø ( k ) s s i ( k) s 1 = ç1 - + { v ( k) - v ( k) } T Ls s conv. (1) i ef_inv v s i ef_ec V dc 3. Cost function V ef_dc V dc V dc The main objective of model pedictive contol Fig. 3. Poposed MPC contol scheme 168 J Elect Eng Technol.015;10(1):

5 Md. Pavez Akte, Saad Mekhilef, Nadia Mei Lin Tan and Hiofumi Akagi the convete. This futue value of thee-phase input AC cuent is is compaed with the efeence cuent i ef_ec of the ectifie mode by utilizing the cost function (e) of Eq. (13). The efeence cuent i ef_ec of the convete in ectifie mode is calculated fom the thee-phase input AC voltage vecto ( v s ) and DC bus voltage ( V dc ) by using PI contolle. Finally, the switching states of the bidiectional AC-DC convete which minimizes cost function, is selected fo next sampling time. Similaly, in invete mode of opeation, the futue value of the thee-phase AC load cuent ( is ) is pedicted by using the discete time Eq. (1). Hence, the optimizing switching states ae selected fo fiing the switches by using cost function (13). 3.4 Contol algoithm Fig. 4 pesents the contol algoithm of MPC method fo the thee-phase bidiectional AC-DC convete. The whole pedictive contol pocess completes the following steps fo selecting the optimized switching state of the convete in the next sampling inteval (k+1). The contol algoithm stats with measuing and sampling the thee-phase AC cuent is ( k) fo the k th sampling peiod. Afte sampling this thee-phase AC cuent, the futue value of this cuent is is pedicted by using the discete time equation of the convete in next (k+1) th sampling peiod. Then the efeence cuents fo the ectifie mode ( i ef_ec ) and invete mode ( i ef_inv ) ae calculated and set to coespond with the amount of desied powe flow. Theefoe, the cost function (e) of the thee-phase bidiectional AC-DC convete is calculated with the pedicted and efeence values of gid cuent. Finally, the switching state associated with the minimum cost function is finally selected fo fiing the convete in the next sampling time peiod (k+1). 4. Simulation Results The poposed MPC algoithm is caied out by using MATLAB/Simulink to validate the feasibility of the contol method. To veify the poposed contol method of bidiectional AC-DC convete fo enegy stoage system, both the ectifie and invete mode of opeations have been investigated fo powe tansfe between thee-phase AC voltage side and DC voltage bus. The paametes shown in Table ae used in the simulation of the ectifie and invete modes with the sampling time of 50 µs. Fig. 5 shows the thee-phase AC (phase-neutal) voltage and cuent of the bidiectional AC-DC convete in both the ectifie and invete modes with instant mode changing capability. Duing the ectifie mode, the convete is opeated as a font end ectifie. Theefoe, the efeence cuent is fixed with PI contolle to tansfe powe fom thee-phase AC voltage souce to DC bus by contolling the input cuent, in which the output DC voltage is fixed at 70 V. Results in Fig. 5(a) show that, the AC phase voltage and cuent ae exactly in phase, which ensue the unity powe facto. Again in invete mode, the bidiectional AC-DC convete allows powe tansfe fom DC voltage bus to AC voltage end by keeping the phase voltage and cuent in 180 o phase shift. Theefoe, the unity powe facto is also maintained vey accuately duing this opeating mode. Fig. 5(b) shows the phase-to-phase AC voltage geneated by the convete. On the othe hand, the thee- Table. Simulation and expeimental paametes Fig. 4. Poposed MPC contol algoithm Paametes values and unit Vaiables and Paametes Values Unit Powe Rating (P) 3.0 kw Thee-phase Gid Voltage (v g) 110 V (ms) Gid Fequency (f s) 50 Hz DC bus Voltage (V dc) 70 V Input Filte Inductance (L s) 5 mh Input Filte esistance (R s) 0.1 Ω Sampling Time (T s) 50 µs Load esistance (R Load) 50 Ω DC link Capacito (C dc) 1000 µf 169

6 Model Pedictive Contol of Bidiectional AC-DC Convete fo Enegy Stoage System phase AC cuent dawn by the convete in ectifie mode and injected by the convete in invete mode, is pesented in Fig. 5(c). Duing the ectifie mode, the cuent dawn by the convete is contolled using PI contolle at a value of 6 A (peak) fo each phase cuent. Fig. 5(c) shows that, each phase AC cuent is accuately tacking the efeence value, which veifies the feasibility of the model pedictive contol method. In invete mode, the efeence cuent is also fixed at a value of 6 A (peak) pe phase. Theefoe, the output cuent cooboates the accuacy of the poposed contol method by accuately tacking the efeence cuent. Futhemoe, the MPC algoithm effectively educes the THD of AC cuent by accuately tacking the sinusoidal efeence cuent, which is pesented in Fig. 5(e). The DC bus voltage and cuent ae depicted in Fig. 5(d). The DC voltage pulsations ae vey low in both the opeating modes. The instantaneous opeating-mode changing capability is one of the most attactive advantages of the convete with model pedictive contol method. The positive value (5.10 A) of DC cuent means that, the bidiectional AC-DC convete is woking in ectifie mode and the powe is tansfeing fom theephase AC souce to enegy stoage device. On the othe hand, the DC cuent goes to negative value ( 5.05 A) duing the invete mode of opeation. 5. Expeimental Veifications A 3.0 kw scaled down laboatoy pototype of the bidiectional AC-DC convete that has been developed fo the enegy stoage system. The expeimental setup is pesented in Fig. 6. The same paametes as in Table ae employed. Duing the expeimentation, a thee-phase potable powe supply [KOSIJAYA, MODEL: KA19530] was used fo voltage supply and STMICROELECTRONICS - STGW0NC60VD IGBT, 600V, 0A was used as powe devices. Moeove, inducto [SMP, MODEL: , S:0004] was used as filte inducto and esisto [TERCO, MODEL: MV1100] was used as a esistive load. The expeimental veification of the poposed model Fig. 5. Simulation esults of the bidiectional AC-DC convete fo both ectifie and invete mode: (a) AC phase voltage and cuent; (b) phase to phase AC voltage geneated by the convete; (c) theephase AC cuent; (d) DC bus voltage and cuent and (e) AC cuent tacking with efeence. Fig. 6. Expeimental system of the bidiectional AC-DC convete with model pedictive contol 170 J Elect Eng Technol.015;10(1):

7 Md. Pavez Akte, Saad Mekhilef, Nadia Mei Lin Tan and Hiofumi Akagi (e) Fig. 7. Expeimental esults: (a) AC phase voltage and cuent at ectifie mode; (b) AC phase voltage and cuent at invete mode; (c) DC bus voltage and cuent at ectifie mode; (d) DC bus voltage and cuent at invete mode; (e) THD of AC cuent at ectifie mode, and (f) THD of AC cuent at invete mode. (f) pedictive contolled bidiectional AC-DC convete is caied out by using the apid pototyping and eal-time inteface system dspace with DS1104 contol cad which consist of Texas Instuments TMS30F40 sub-pocesso and the Powe PC 603e/50 MHz main pocesso. This dspace contol desk woks togethe with Mathwok MATLAB/Simulink R011b eal-time wokshop and eal-time inteface (RTI) contol cads to implement the poposed MPC algoithm. The voltage is measued with diffeential pobe [PINTEK DP-5] and the cuent with cuent tansduce [LEM LA 5-NP]. Fig. 7(a) shows that the thee-phase AC phase voltage and cuent ae exactly in phase duing the ectifie opeation mode, which ensues the unity powe facto. Again in the invete mode, the convete allows powe tansfe with unity powe facto fom the DC voltage bus to AC voltage end by keeping the phase voltage and cuent with an 180 o phase shift, as pesented in Fig. 7(b). The DC bus voltage and cuent fo both opeating modes ae depicted in Figs. 7(c) and 7(d). The esults illustate that the DC voltage ipple and the pulsation in DC cuent ae vey low duing both opeating modes. Duing ectifie mode, the DC-link efeence voltage (V dc ) is vaied fom 70 V to 30 V to check the stability and tansient esponsiveness of the MPC contol algoithm. Figs. 7(a) and 7(c) show the expeimental esults of AC phase cuent, DC bus voltage and cuent that have been changed and eached its steady state level within vey shot time (less than 0 ms). This apid step change confims the fast esponse of the PMC method. Fig. 7(c) also shows that the steady state output of DC-link voltage and cuent 171

8 Model Pedictive Contol of Bidiectional AC-DC Convete fo Enegy Stoage System emain linea in wide ange of time with vey low voltage and cuent ipple, which ensue the stability and good pefomance of the poposed MPC algoithm. Similaly, the stability and esponsiveness of the poposed MPC method fo AC-DC convete have been tested with Figs. 7(b) and 7(d) by vaying the AC efeence cuent ( i ef_inv ), duing the invete mode of opeation. Finally, the hamonic analysis of thee-phase AC cuent fo both ectifie and invete mode is illustated in Figs. 7(e) and 7(f), which show that the total hamonic distotion (THD) is 3.3% and 3.5% in the ectifie and invete modes, espectively. The THD of gid cuent is measued with FLUKE 1735 Powe Logge. The accuacy of this powe logge is ±0.% of its full scale. 6. Efficiency Compaison The efficiency of MPC contolled bidiectional AC-DC convete is measued with FLUKE 1735 Powe Logge. The accuacy of this powe logge is ±0.% of its full scale. The efficiencies of AC-DC convete ae measued in MPC method against the powe tansfe anges fom 0.5 kw to 3.0 kw. In ode to confim the effectiveness of MPC algoithm, the efficiencies of MPC contolled bidiectional AC-DC convete ae compaed with conventional VOCbased PWM contolled bidiectional AC-DC convete fo both the ectifie and invete mode of opeation, pesented in Fig. 8 and Fig. 9. The VOC-based PWM method is applied in the 3.0 kw bidiectional AC-DC convete topology with employing the same paametes and measuement techniques as in MPC algoithm. Although, MPC algoithm has vaiable switching fequency poblem, the efficiencies associated with the MPC contol ae highe compaed to the VOC-based PWM contol method due to the elimination of eactive powe, minimized DC voltage ipple and low THD level. Fig. 8 shows the efficiency compaison of the convete in ectifie mode. The maximum efficiency is 96.8% using the MPC method and Fig. 9. Efficiency compaison between MPC and VOCbased PWM contol method duing invete mode of opeation. it is 95.6% using the VOC-based PWM method, at the powe tansfe of kw. On the othe hand, Fig. 9 descibes the efficiency compaison of poposed MPC contolled AC-DC convete with the conventional VOC-based PWM contolled convete duing the invete mode. The maximum efficiency associated with the MPC contol algoithm is 96%, while the highest efficiency associated with VOC-based PWM contolle is 95% duing the invete mode of opeation at.0 kw. It can be seen that the efficiencies of the bidiectional AC-DC convete decease with the incease of the powe tansfe. The flow of cuent inceases with the powe tansfe which esults the incease of conduction and switching loss. But, still the MPC algoithm shows the bette efficiency than the VOCbased PWM contol method fo the whole anges of powe tansfe. 7. Conclusion In this pape, a model pedictive contolled bidiectional AC-DC convete is pesented fo enegy stoage system to tansfe powe between thee-phase AC voltage souce and DC voltage bus. MPC is a poweful contol algoithm in the field of bidiectional AC-DC powe convetes which povides bidiectional powe flow with instantaneous mode changing capability and fast dynamic esponse. The most impotant outcomes of this investigation ae as follows: Fig. 8. Efficiency compaison between MPC and VOCbased PWM contol method duing ectifie mode of opeation. The thee-phase bidiectional AC-DC convete is opeated with unity powe facto in both the ectifie and invete modes of opeation. The total hamonic distotions (THD) ae 3.3% and 3.5% duing the ectifie and invete opeating modes, espectively, which ae within the accepted limit. The DC voltage and cuent ipples ae vey low duing both opeating mode. Highe efficiency achieved compaed to the VOC PWM method. 17 J Elect Eng Technol.015;10(1):

9 Md. Pavez Akte, Saad Mekhilef, Nadia Mei Lin Tan and Hiofumi Akagi The esults associated in this investigation ae vey much encouaging and will continue to play a stategic ole in the impovement of moden high pefomance bidiectional AC-DC convete in enegy stoage system and will open a new pospect in the powe electonics eseach. Acknowledgements The authos would like to thank the Ministy of Highe Education and Univesity of Malaya fo poviding financial suppot though HIR-MOHE poject UM.C/HIR/MOHE/ ENG/4 and UMRG poject No. RP006E-13ICT. Refeences [1] J. M. Caasco, L. G. Fanquelo, J. T. Bialasiewicz, E. Galván, R. P. Guisado, M. A. Pats, et al., Poweelectonic systems fo the gid integation of enewable enegy souces: A suvey, IEEE Tansactions on Industial Electonics, vol. 53, pp , 006. [] Y. Chen and K. Smedley, Thee-phase boost-type gid-connected invete, IEEE Tansactions on Powe Electonics, vol. 3, pp , 008. [3] X. Hu, K. Tseng, Y. Liu, S. Yin, and M. Zhang, A high fequency isolated cuent-fed bidiectional DC/ AC convete fo gid-tied enegy stoage system, in ECCE Asia Downunde (ECCE Asia), 013 IEEE, 013, pp [4] H.-T. Yau, C.-J. Lin, and Q.-C. Liang, PSO Based PI Contolle Design fo a Sola Chage System, The Scientific Wold Jounal, vol. 013, 013. [5] N. M. L. Tan, T. Abe, and H. Akagi, Design and pefomance of a bidiectional Isolated DC-DC convete fo a battey enegy stoage system, IEEE Tansactions on Powe Electonics, vol. 7, pp , 01. [6] P. Cotés, J. Rodíguez, P. Antoniewicz, and M. Kazmiekowski, Diect powe contol of an AFE using pedictive contol, IEEE Tans. Powe Electon., vol. 3, pp , 008. [7] A. Alias, N. A. Rahim, and M. A. Hussain, Bidiectional thee phase powe convete, in Clean Enegy and Technology (CET), 011 IEEE Fist Confeence on, 011, pp [8] B. Singh, S. Gaiola, B. N. Singh, A. Chanda, and K. Al-Haddad, Multipulse AC-DC convetes fo impoving powe quality: a eview, IEEE Tans. Powe Electon., vol. 3, pp , 008. [9] B. Singh, B. N. Singh, A. Chanda, K. Al-Haddad, A. Pandey, and D. P. Kothai, A eview of thee-phase impoved powe quality AC-DC convetes, IEEE Tans. Ind. Electon., vol. 51, pp , 004. [10] P. Vedelho and G. Maques, DC voltage contol and stability analysis of PWM-voltage-type evesible ectifies, IEEE Tans. Ind. Electon., vol. 45, pp , [11] M. Malinowski, M. P. Kazmiekowski, and A. M. Tzynadlowski, A compaative study of contol techniques fo PWM ectifies in AC adjustable speed dives, IEEE Tans. Powe Electon., vol. 18, pp , 003. [1] D. Zhi, L. Xu, and B. W. Williams, Impoved diect powe contol of gid-connected DC/AC convetes, IEEE Tansactions on Powe Electonics, vol. 4, pp , 009. [13] T. Noguchi, H. Tomiki, S. Kondo, and I. Takahashi, Diect powe contol of PWM convete without powe-souce voltage sensos, IEEE Tansactions on Industy Application, vol. 34, pp , [14] I. Takahashi and Y. Ohmoi, High-pefomance diect toque contol of an induction moto, IEEE Tansactions on Industy Application, vol. 5, pp , [15] C. Lascu, I. Boldea, and F. Blaabjeg, A modified diect toque contol fo induction moto sensoless dive, IEEE Tansactions on Industy Application, vol. 36, pp , 000. [16] S. Vazquez, J. A. Sanchez, J. M. Caasco, J. I. Leon, and E. Galvan, A model-based diect powe contol fo thee-phase powe convetes, IEEE Tans. Ind. Electon., vol. 55, pp , 008. [17] D. Zhi, L. Xu, B. W. Williams, L. Yao, and M. Bazagan, A new diect powe contol stategy fo gid connected voltage souce convetes, in Poc. Int. Conf. Elect. Machines and Syst. (ICEMS), 008, pp [18] A. Bouafia, F. Kim, and J.-P. Gaubet, Fuzzy-logicbased switching state selection fo diect powe contol of thee-phase PWM ectifie, IEEE Tans. Ind. Electon., vol. 56, pp , 009. [19] J. Hu, L. Shang, Y. He, and Z. Zhu, Diect active and eactive powe egulation of gid-connected DC/AC convetes using sliding mode contol appoach, IEEE Tans. Powe Electon., vol. 6, pp. 10-, 011. [0] S. Kouo, P. Cotés, R. Vagas, U. Ammann, and J. Rodíguez, Model pedictive contol - A simple and poweful method to contol powe convetes, IEEE Tans. Ind. Application, vol. 56, pp , 009. [1] J. Rodiguez, M. Kazmiekowski, J. Espinoza, P. Zanchetta, H. Abu-Rub, H. Young, et al., State of the At of Finite Contol Set Model Pedictive Contol in Powe Electonics, IEEE Tans. Powe Electon., 013. [] J. Rodiguez, J. Pontt, C. A. Silva, P. Coea, P. Lezana, P. Cotés, et al., Pedictive cuent contol of a voltage souce invete, IEEE Tans. Ind. Electon., vol. 54, pp , 007. [3] S. Muslem Uddin, P. Akte, S. Mekhilef, M. Mubin, 173

10 Model Pedictive Contol of Bidiectional AC-DC Convete fo Enegy Stoage System M. Rivea, and J. Rodiguez, Model pedictive contol of an active font end ectifie with unity displacement facto, in Poc. IEEE Int. Conf. Cicuits and Systems (ICCAS), 013, pp [4] D. E. Quevedo, R. P. Aguilea, M. A. Péez, P. Cotés, and R. Lizana, Model pedictive contol of an AFE ectifie with dynamic efeences, IEEE Tansactions on Powe Electonics, vol. 7, pp , 01. [5] M. Pavez, S. Mekhilef, N. M. Tan, and H. Akagi, Model pedictive contol of a bidiectional AC-DC convete fo VG and GV applications in electic vehicle battey chage, in Poc. IEEE Tanspotation Electification Conf. and Expo (ITEC), 014, pp [6] S. Muslem Uddin, S. Mekhilef, M. Rivea, and J. Rodiguez, A FCS-MPC of an induction moto fed by indiect matix convete with unity powe facto contol, in Industial Electonics and Applications (ICIEA), 013 8th IEEE Confeence on, 013, pp [7] M. Uddin, S. Mekhilef, M. Mubin, M. Rivea, and J. Rodiguez, Model Pedictive Toque Ripple Reduction with Weighting Facto Optimization Fed by an Indiect Matix Convete, Electic Powe Components and Systems, vol. 4, pp , 014. [8] M. Uddin, S. Mekhilef, M. Rivea, and J. Rodiguez, Pedictive indiect matix convete fed toque ipple minimization with weighting facto optimization, in Powe Electonics Confeence (IPEC-Hioshima 014-ECCE-ASIA), 014 Intenational, 014, pp Md. Pavez Akte was bon in Pabna, Bangladesh. He eceived the B.Sc. degee fom Chittagong Univesity of Engineeing and Technology (CUET), Chittagong, Bangladesh, in 011. In 011, He joined the Reseach and Development (R&D) depatment of the HAMKO Copoation Ltd, Bangladesh as an Executive Enginee. Cuently he is continuing the M.Sc. degee and woking as a eseach assistant with the Powe Electonics and Renewable Enegy Reseach Laboatoy (PEARL), Depatment of Electical Engineeing, Univesity of Malaya, Kuala Lumpu, Malaysia. His eseach inteest is on powe convetes and electical dives, bidiectional powe convesion techniques, pedictive and digital contol, enewable enegy, and wieless powe tansfe. Saad Mekhilef eceived the B.Eng. degee in Electical Engineeing fom the Univesity of Setif, Setif, Algeia, in 1995, and the Maste of Engineeing Science and Ph.D. degees fom the Univesity of Malaya, Kuala Lumpu, Malaysia, in 1998 and 003, espectively. He is cuently a Pofesso at the Depatment of Electical Engineeing, Univesity of Malaya, Kuala Lumpu. He is the autho o coautho of moe than 50 publications in intenational jounals and poceedings. He is a Senio Membe of the IEEE. He is actively involved in industial consultancy, fo majo copoations in the powe electonics pojects. His eseach inteests include powe convesion techniques, contol of powe convetes, enewable enegy, and enegy efficiency. Nadia Mei Lin Tan was bon in Kuala Lumpu, Malaysia. She eceived the B.Eng. (Hons.) degee fom the Univesity of Sheffield, Sheffield, U.K., in 00, the M. Eng. degee fom Univesiti Tenaga Nasional, Kajang, Malaysia, in 007, and the Ph.D. degee fom Tokyo Institute of Technology, Tokyo, Japan, in 010, all in electical engineeing. Since Octobe 010, she has been a Senio Lectue in the Depatment of Electical Powe Engineeing, Univesiti Tenaga Nasional. He cuent eseach inteests include powe convesion systems and bidiectional isolated dc dc convetes. D. Tan is a Gaduate Membe of the Institution of Enginees Malaysia (IEM) and a Membe of the Institution of Engineeing and Technology (IET). Hiofumi Akagi was bon in Okayama, Japan, in He eceived the B.S. degee fom the Nagoya Institute of Technology, Nagoya, Japan, in 1974, and the M. S. and Ph. D. degees fom the Tokyo Institute of Technology, Tokyo, Japan, in 1976 and 1979, espectively, all in electical engineeing. In 1979, he was with the Nagaoka Univesity of Technology, Nagaoka, Japan, as an Assistant and then Associate Pofesso in the Depatment of Electical Engineeing. In 1987, he was a Visiting Scientist at the Massachusetts Institute of Technology, Cambidge, MA, fo ten months. Fom 1991 to 1999, he was a Pofesso in the Depatment of Electical Engineeing, Okayama Univesity, Okayama, Japan. Fom Mach to August of 1996, he was a Visiting Pofesso at the Univesity of Wisconsin, Madison, and then the Massachusetts Institute of Technology. Since Januay 000, he has been a Pofesso in the Depatment of Electical and Electonic 174 J Elect Eng Technol.015;10(1):

11 Md. Pavez Akte, Saad Mekhilef, Nadia Mei Lin Tan and Hiofumi Akagi Engineeing, Tokyo Institute of Technology, Tokyo, Japan. His eseach inteests include powe convesion systems, ac moto dives, active and passive EMI filtes, highfequency esonant invetes fo induction heating and coona dischage teatment pocesses, and utility applications of powe electonics such as active filtes fo powe conditioning, self-commutated BTB systems, and FACTS devices. He has authoed o coauthoed moe than 80 IEEE Tansactions papes, and two invited papes in Poceedings of the IEEE. Accoding to Google Schola, the total citation index fo all his papes is moe than 6,000. He has made pesentations many times as a keynote o has been an invited speake intenationally. Since Januay 007, he has been the Pesident of the IEEE Powe Electonics Society (PELS). He was elected as a Distinguished Lectue of the IEEE Industy Applications Society (IAS) and PELS fo He eceived two IEEE IAS Tansactions Pize Pape Awads in 1991 and 004, and two IEEE PELS Tansactions Pize Pape Awads in 1999, and in 003, nine IEEE IAS Committee Pize Pape Awads, the 001 IEEE William E. Newell Powe Electonics Awad, the 004 IEEE IAS Outstanding Achievement Awad, and the 008 IEEE Richad H. Kaufmann Technical Field Awad