Bidirectional step-up/step-down DC-DC converter with magnetically coupled coils

Transcription

1 Biirectional step-up/step-own DC-DC converter with magnetically couple coils Frivalský M.*, Dobrucký B.*, Scelba G.**, Špánik P.*, Drgoňa P.* * University of Zilina, Department of Mechatronics an electronics, 26 Zilina, Slovakia ** Universita egli stui i Catania, Dipartimento i ingegneria, Catania, Italy michal.frivalsky@fel.uniza.sk Abstract. The paper is focuse on biirectional up/own DC-DC Converter with magnetically couple coils (MCC), which can be utilize as a part of power semiconuctor system in traction, automotive, or inustrial applications like renewable energy sources. Propose solution of main circuit of biirectional converter shoul serve for energy transfer from source to loa, an vice versa, whereby parameters of electrical variables like voltage, current an power are able to be aapte base on the current requirements of application. Their values can be increase or ecrease in first (energy transfer from source to loa) or in thir (energy transfer from loa to source) quarant of converter's operation. The boost effect of output voltage can be increase - if it is not sufficient one - by appropriate ratio of number of inuctor winings. Keywors: DC-DC power converter, biirectional step-up/step-own converter, uty cycle factor, transfer function, parasitic parameters, steay-state operation.. Introuction Process of energy recuperation is well known phenomena, especially in the fiel of traction applications. Nowaays, the recuperation of energy is use almost in the inustrial, commercial an also in the consumer sector. The main factor, which allows this breakthrough, was evelopment of technology in prouction of power semiconuctor structures an research of new topologies of main circuit of switche moe power supplies (SMPS), which are working in two-quarant (2Q biirectional) operation[]-[3]. Although, there are now a variety of schemes of DC/DC biirectional converters, the isavantage of these solutions is high complexity, or lack of versatility, which is associate with limite utilization of mentione topologies. The main reason of this, are specific requirements for their properties, particularly possibility of change of electrical values as wie as possible. Another isavantage of existing solutions in terms of universal utilization is relatively high material costs. Nowaays, the existing solutions of biirectional converters can by ivie as follows:the first group inclues cascae DC/DC converters in buck-boost topology, secon group are non-isolate half-brige topologies, in another group the multi-tank non-isolate Cuk an Sepic topologies are presente an last group involves so-calle split topologies, using pi-filters at the input an output of converter. The mentione rawback in the comparison with propose solution is consierably higher number of components in the system resulting in higher complexity of topology, lack of versatility an insufficient ynamical range of input an output parameters

2 2. Biirectional step-up/step-own converter with MCC The main circuit of propose converter, base on boost DC-DC converter [4]-[6], composes from three main parts (Fig.). The first is given by primary capacitive filter together with primary transistor T. Secon part consists from most important part of converter - bifilarly woune coil, whose winings are connecte in orer to create auto-transformer with common groun on the primary an seconary sie. If target application requires total galvanic isolation between primary an seconary sie, it is possible to realize propose converter as isolate biirectional converter. This approach can be also one by simple moification of main circuit with the use of auxiliary switch. The last, thir part of propose converter is compose from seconary transistor T2, from filter an from loa/appliance. Fig. Block scheme of propose biirectional DC-DC converter with MCC [7] From fig. can be seen, that primary as well as seconary part of converter have in principle the same functionality. Base on this property both parts can behave as input or output of converter (the seconary sie is issymmetrical to primary sie), an therefore the energy transfer from source to loa an vice versa can be simply an effectively realize. Simultaneously the moification of the electrical variables magnitues (increase or ecrease) can be one in wie regulation range. Base on the operating conitions, the converter functionality is hel in first- or thir quarant of operating characteristic. The main avantages compare to other solution of biirectional DC/DC converters are: - extra-wie regulation range of electrical variables at given output (step-up/step-own) - low complexity of main circuit, within achievement of high universality - possibility of isolate an non-isolate version The analysis of propose converter The propose converter, whose principal schematic is shown infig. is classifie as DC-DC converter. The following analysis is oriente on the etermination of state space variables an on the investigation of voltage-transfer characteristic in both irect an recuperative moe of operation.

3 The operation of converter both for irections (energy transfer from source into loa) an for recuperative (energy transfer from loa into source) moe can be ivie into two operating intervals: - interval I<t - t >: transistor T (T 2 ) close, transistor T 2 (T ) open; - interval II<t - T>: transistor T (T 2 ) open, transistor T 2 (T ) close. Fig.2 shows schematics of propose converter, whereby parasitic resistances are consiere, an ue to fact, that their presence is influencing voltage transfer characteristic. This impact is negative, an therefore must be accepte uring state space moel setting an its consequent erivation. Fig. 2 Block scheme of propose biirectional DC-DC converter with MCC The state space moel for propose converter is erive for the operating conition, when converter operates at irect moe. Here it must be note, that consiering recuperative operating moe, the state space will be the same, whereby only one change apply specifically for the input/output arguments in the case of voltages an currents (input will act as output an vice versa). Interval I<t - t > where: Interval II<t - T> = + is the current in the primary sie isoutput capacitor voltage is the sum of series parasitic resistances is the parallel parasitic resistances is value of primary inuctance is input voltage is loa resistance +, () = + + (2) The voltage transfer characteristic can be erive from the comparison of ripple current uring first an secon interval. The analysis outgoes from the equation of inuctor's voltage: =. $ $ After linearization, next formula is vali for ripple current: (3) ' =.(.), (4)

4 where: ( is uty cycle ) is switching perio of converter Comparing the value of ripple current uring interval when transistor T is close with the ripple current from the interval when transistor T is open leas to:.(.) =.( ().). (5) When L = L 2, thus N = N 2, where N an N 2 are number of primary respectively seconary turns an all parasitic resistances are neglecte, then next equation for approximate computation of voltage transfer function can be written: ( = ( (). (6) Fig. 3 is showing graphical interpretation of voltage transfer characteristic with ieal waveform (without parasitic ones), an voltage transfer waveform, when parasitic resistances are being consiere. 3. Simulation investigations of propose converter s properties In this chapter we woul like to investigate the voltage transfer functions of propose converter base on parametrical simulations from OrCAD/Pspice. Base on this, an after comparisons with theoretical assumptions it is possible to emonstrate existing eviations in voltage transfer function. Next figure is showing voltage transfer function of propose converter whose input/output parameters are as follows: -. = 24 V, 2 = 5 khz, = = 3 μh (7 = 7 ), 89: = var., ' 89: = var, > 89: = max.25 W, loa resistance = 48 Ω, Parasitics =.24,.48,.96 an.44 Ω: U2/U rs=.48ω rs=.96ω rs=.44ω rs=.24ω rs=ω uty cycle Fig. 3 Voltage transfer function of propose converter at % power loaing an various parasitic resistances from to.44 Ohm

5 Loa, 2 an 2%, R=48, 24 an 24 Ω: U2/U % loa 2% loa 2% loa uty cycle Fig. 4 Voltage transfer function of propose converter at 2, an 2 % of power loaing There is evient from Figs. 3 an 4 that - iealize relation of voltage transfer ration on uty cycle( (i.e.= ( ( ) is not vali for entire range of uty cycle ( ; ; - consequently, voltage transfer characteristic is not monotonic one but it has a local extreme at which erivative of the transfer is changing;it is critical point of characteristic; - control system use shoul be acting just in secure range from to critical value of uty cycle( LMNO, otherwise it must have variable structure. 4. Experimental verification of biirectional step-up/step-own converter with MCC The experimental set/up was built (Fig. 5) with parameters: -. = 24 V, 2 = 5 khz, = = 3 μh (7 = 7 ), C loa resistance = 48,24,24 Ω, > 89: = var.25 Was maximum, epening on loa resistance. Fig. 5 Experimental set-up of proposebiirectional step-up/step-own converter

6 There are results carrie-out by measurement on experimental set-up of the converter at 2-, -, an 2 % of the loa uner resistive loaing. U2/U % loa 2% loa 2% loa uty cycle Fig. 6 Experimental voltage transfer functions of propose converter at 2-2 % loa Output power can be calculate from the carrie-out transfer characteristics in Fig. 6 > 89: = > QRS = (x24) 48 > QRS = (.4x24) 48 : > QRS = (2x24) 48 = = = = 48 W at ( =.75; = 2 W at uty cycle ( =.5; = 24 W at uty cycle ( =.625; Requeste power (24 W) is possible to calculate also uner 24 Ω loa resistance > QS = (x24) 24 = = 24 W at uty cycle ( =.65. So, for fair esign of converter elements, it is necessary to etermine at what output voltage we want the requeste power. Possible improvements of operation an efficiency of the converter are to be reache by works [8]-[]. 5. Conclusion The biirectional step-up/step-own converter has been presente in the paper. Simulation experiment results, worke-out using OrCAD/PSpice programming environment, have shown that voltage transfer characteristics feature by two parts: the first one with positive erivative part, an the secon one with negative erivative part. Maximal output voltage oesn t epen only on uty cycle of electronic switches but also on the parasitic parameter values of the converter circuit elements. The experimental set/up measurements have verifie results of simulation an theoretical assumes. Presente solution of biirectional converters base on buck-boost DC/DC topologyconsists of substantial lesser components as classical cascae DC/DC converters or non-isolate half-brige topologies,an features: by extremely wieregulation range of output voltage, low complexity of main

7 circuit, within achievement of high universality, an possibility of isolate an non-isolate version. Such a converter system can be utilize as a part of power semiconuctor system in traction, automotive, or inustrial applications like renewable energy sources. As a future works we suppose the investigation of transient behavior -, efficiency analysis- an control system esign of that type of biirectional step-up/step-own converter. Acknowlegement The authors wish to thank for the financial support to Slovak Research an Development Agency project No. APVV 38 an R&D operational program Centre of excellence of power electronics systems an materials for their components No. OPVaV-28/2./-SORO, ITMS fune by European regional evelopment fun (ERDF). References [] LUO, F.L., YE, H.: Power Electronics Avance Conversion Technologies. CRC Press, Boca Raton (USA, FL), 2, ISBN [2] SZYCHTA, E.: Multi-Resonant ZVS Converter of DC/DC Voltage Type (in Polish). Monograph, Oficyna Wyawnicza Uniwersytetu Zielonogórskiego, 26. [3] BERES, T., DUDRIK, J., EOTVOS E.: Biirectional step-up/step-own DC-DC converter for Hybri Battery (in Slovak).EE-Journal for Electrical Engineering an Electro-Energetics,Vol. 7, No. (Feb. 2), pp. 3-32, ISSN [4] HIMMELSTOSS, F. A., VOTZI, H. L.: Combine Forwar-Flyback-Converter with Only Two Dioes Function An Moelling.Communications-Scientific Letters of ZU, 2a/2, pp [5] LUFT, M., SZYCHTA, E., SZYCHTA, L.: Metho of esigning ZVS boost converter // 3th Power Electronics an Motion Control Conference - EPE-PEMC Poznan (PL), 28 P [6] DOBRUCKY, B., HRABOVEC, L., POPRENDA, J.: Power Supply of Increase Exciting Voltage of Static Exciter for Traction Generator GPA-6 (in Slovak), Research Report No. V- 767/88, EVPU a.s., Nova Dubnica (SK), March 988. [7] FRIVALDSKY, M.,DOBRUCKY, B., SPANIK, P.: Biirectional step-up/step-own DC-DC converter with magnetically couple coils(in Slovak), Application on Inustrial TemplatePÚV No. N/A, submitte: Apr. 8, 23. [8] DUDRIK, J., TRIP, N. D.: Soft- Switching PS-PWM DC-DC Converter for Full-loa Range Applications, IEEE Transactions on Inustrial Electronics, Vol. 57, no. 8 (2), p [9] DOBRUCKY, B., SPANIK, P., SUL, R.:Improvement of Power Electronic Structure Characteristics Using SiC Technology An Overview.Communications-Scientific Letters of ZU,/26, pp [] SPANIK, P., DOBRUCKY, B., FRIVALDSKY, M., DRGONA, P.: Experimental analysis of commutation process of power semiconuctor transistor structures, ActaTechnica CSAV, Vol. 52 (27), No. 4., pp , ISSN -743.