Three-phase diode rectifier with the current modulator based on multi-channel converter in a DC circuit

Transcription

1 ichał GWÓŹDŹ, ichał KRYSTKOWIAK 1 Politechnika Poznańka, Wydział Elektryczny, Intytut Elektrotechniki i Elektroniki Przemyłowej, Zakład Energoelektroniki i Sterowania (1) Three-phae diode rectifier with the current modulator baed on multi-channel converter in a DC circuit Abtract. In thi paper a 3-phae power diode rectifier ytem with quai-inuoidal input (power grid) current i preented. In order to benefit from it, the current modulation in a DC circuit of rectifier i ued. The eential part of the current modulator i a wide-band power electronic controlled current ource baed on a multichannel converter. Work of a modulator control ytem i baed on the Generalized Sampling Expanion a an extenion of the Whittaker-Kotelnikov-Shannon (WKS) ampling theory. The current modulator control algorithm repect impact of aliaing phenomena at ytem tability uing the method propoed by one of author. The paper include the rectifier ytem decription and rule of work of the current modulator. Alo, ome reult of reearch on both a full rectifier imulation model and a current modulator laboratory prototype are preented. Keyword: control method of electrical ytem, diode rectifier, Generalized Sampling Expanion, multi-channel converter, PW Introduction The power rectifier belong to a very widely utilized group of power electronic converter. Unfortunately, a tandard diode and thyritor rectifier work i the reaon for ditortion of current and voltage in a power grid. It ha caued a very eriou problem for the energetic ytem for many year thu, improving quality of input (power) grid current of rectifier i often neceary. A one of olution obtaining it i rectifier baed on uing a paive or active filter at the input [1,]. The following way relie on uing of o call active rectifier, which i built with tranitor (IGBT) inverter witched at frequency which i everal time higher than frequency of voltage ource in a power grid [3]. Alo, to correct the waveform of the power grid current the rectifier built with diode (or thyritor) being interconnected by mean of coupled inductor can be ued [4]. Another, an advanced olution of rectifier ytem, include of a voltage modulator in the DC circuit of the rectifier. The modulator i built with thyritor and a pecial inductor with everal tap. It ha been conidered e.g. in [5]. All mentioned olution are relatively expenive one. Thu, in thi paper another poible olution being able to hape the waveform of power grid current toward the inuoidal waveform i preented. Thi one i baed on the current modulation in the DC circuit [5, 6]. Such a rectifier ytem i built with two 6-pule diode rectifier, which are upplied by two 3-phae tranformer with the connection tar-tar and tar-delta. In thi way 30 el. deg. phae hift of tranformer output voltage i obtained. Additionally, in a DC circuit a pecial power electronic converter called a current modulator i placed. The current modulator i reponible for haping of the rectifier input current Fig. 1. In fact the tar-tar connected tranformer i not neceary for proper work of the modulator although it help to cale the voltage level of both rectifier in the laboratory prototype of the rectifier ytem [5].

2 Fig. 1. General block diagram of the 3-phae diode rectifier with the current modulator in a DC circuit. The rectifier ytem conit of the following block: two tranformer connected in the tar-delta (TR1) and tar-tar (TR) manner, two tandard 6-pule diode rectifier (DRCT1 and DRCT) with DC circuit connected in parallel, the active (tranitor) rectifier (TRCT) and the current modulator block (CB). The CB i connected to the DC circuit acro the pule tranformer (PT). Rectifier power a common receiver, expreed by. The current modulation conception aume a very large time Z REC contant of the receiver impedance. Similarly like the TR tranformer, the tranitor rectifier i not neceary in the rectifier circuitry too. It role depend on control the voltage level in the DC link of the modulator only without any impact on the modulator output current [5]. Thank to thi rectifier input current are better matched in the inuoidal waveform. The preented olution of the rectifier ytem make it poible to improve ignificantly the quality of rectifier power grid current, and. I.e. waveform of thee are cloe to the inuoidal hape. The current modulator work a a power electronic controlled current ource being connected to the DC circuit of rectifier acro a wide-band pule tranformer with two tap on a primary ite. The i C output current of the modulator i added (with a ign of plu or minu ), with the aid of the PT, to the output current i D1 and of each rectifier in term of the following equation: i D ( i i N i N D D1) 1 N (1) id1 ( irec ic ) N1 1 N id ( irec ic ) N1 N 1 where, equation quantitie are a follow: the PT winding turn ratio, i REC the N receiver current and i C the CB output current. 1 C i A i B i C

3 Thi i the way in which waveform of input current of two rectifier are modified. In conequence, reultant waveform of power grid current of the rectifier ytem (,, and i C ) are modified a well. The power of each, the active rectifier and the current modulator i only 3 % of the total power at the output of the DC circuit. Thi i a great advantage of thi idea of the rectifier ytem. Thank to utilization of an active rectifier the reultant ytem energy efficiency i omewhat improved too. What i alo important, in cae of diabling of the modulator (e.g. due to damage of it) a ytem i able to continue it work a a tandard 1-pule diode rectifier. In order to obtain the inuoidal hape of the power grid current, the modulator current hould atify the following equation [6]: () i C i A i B i C ( t) 3 3 π I REC g co t I REC co(6kgt) co(6kgt co(6k t) co(6k t g g π ) 6 π ) 6 N N 1 : k 0,1,,... However, the complex current form of the equation () can be replaced by a current with triangular hape, with only a mall deterioration of the THD factor of a rectifier input current [6]. The fundamental frequency of the modulator current ha to be equal to 6-time of power grid frequency, i.e. 300 Hz: 4 in(3 6gt) in(5 6gt) (3) ic ( t) IREC in(6 gt)... π 3 5 where g i the fundamental frequency of the voltage in the power grid. THD With uch replacement, auming the power grid i a ymmetrical one, a factor of a power grid current i equal to about 1% [5, 6]. Thu, the current modulator ha to include in it own tructure a wide-band power electronic controlled current ource which would be able to match preciely an output (modulator) current in the reference ignal [7]. Thi feature of the modulator i eential for proper working of the rectifier ytem becaue it determine directly the quality of it input current. Initially, in the current modulator the tandard (i.e. one-channel) inverter ha been implemented. Thi one ha been a part of the laboratory prototype of rectifier ytem [5]. The preent article i focued mainly on utilizing in a current modulator a wide-band power electronic controlled current ource baed on a multi-channel (interleaved) converter [8, 9]. The whole text i divided into 6 ection. The firt one deal with the general rectifier conception. The econd one how a baic decription of the wide-band power electronic controlled current ource baed on a multi-channel converter. In the third ection, an iue of controlled ource tability i conidered. The fourth ection preent mainly, among other item, a imulation model of the rectifier ytem. In the fifth ection

4 elected reult of reearch on a laboratory prototype of the current modulator are preented. The lat part i dedicated to concluion. Wide-band power electronic controlled current ource Dynamic change of parameter of energy ource and receiver are the reaon for decreaing exactitude of output ignal toward reference ignal. In order to improve thee parameter often more advanced olution of power electronic converter are neceary. They can be exemplified by a wide-band power electronic voltage controlled voltage ource (VCVS) or voltage controlled current ource (VCCS). Such a converter hould match an output ignal preciely in a reference waveform o that both a modified electrical tructure of a converter and an effective control algorithm are neceary. It ha many application in a power electronic equipment. In Fig. a general tructure of the VCCS i hown. It i baed on the conception of a multi-channel converter where a total output current i proportional to the um of current i i : i 0,1,..., 1 in individual channel of a converter. L, i L The VCCS i a ytem which work in a cloed, voltage type, negative feedback loop. Inverter in an execution block of the VCCS are controlled in PW mode with the contant value of a carrier frequency [7]. One of the fundamental block of the VCCS i a paive low-pa filter at the output of power tage coniting of a et of connected in parallel inductor. Thi filter ha two baic tak to do, namely it obtain the uitable value of the output impedance of a converter and minimize amplitude of PW carrier component in the output current, making it poible for the converter to meet requirement of EC. Fig.. Block diagram of the VCCS. The general tructure of the VCCS i baed on two module, the control module (C) and the execution module (E). The control module include the following internal block: adder (A), producing the error ignal uerr uref ufb, regulator of the output current with the gain factor of, -order multi-dimenional ample-and-hold ytem (SHS) coniting of connected in parallel ample-and-hold amplifier. The execution module conit of: -connected in parallel half-bridge type inverter, output filter ( L i : i 0,1,..., 1 ), E, current tranducer (CT), producing the feedback voltage u fb, being proportional to the VCCS output current i L. k 0

5 The E i loaded by the controlled by the reference voltage Z L impedance and ZL j LL R at the input of the C. u ref L. The VCCS i The ampling moment and PW carrier ignal in individual channel of the converter are hifted with each other by T, where T i a mater ampling period. In reult, from the point of view of ytem tability, the converter tranfer function i preferably modified [10]. Thank to thi, the regulator gain in the VCCS control ytem can be increaed compared to an one-channel converter. It ha a very poitive impact on the performance of the VCCS becaue a control algorithm let more accurately match the VCCS output current in a reference one. Owing to hifting alo by time T of carrier ignal in individual channel of the E the effective carrier frequency in the output ignal i hifted -time toward higher frequencie. In conequence, the amplitude of current ripple in the converter output current, caued by pule modulation, i reduced ignificantly a well. In thi particular cae of work of the VCCS in a rectifier ytem, the tructure of the VCCS ha been lightly modified. It ha been neceary due to way of including the pule tranformer in thi ytem baed on a virtual ground. A a reult, the x-channel modified inverter in the E of the VCCS ha been ued. The block cheme of the VCCS i preented in Fig. 3. Fig. 3. Block diagram of the VCCS for driving the pule tranformer. The modulation ued in pule modulator i two-ided and aymmetric. The load of the VCCS the pule tranformer i included in the circuit in a differential manner. I.e. voltage at the output of the INV inverter pair ha to be in anti-phae with repect to 0, x the voltage at the output of the INV pair. Becaue of =, ampling moment in the T SHA 1 and SHA 0 hould be hifted with each other by a 1, x time. Taking into account the pule modulation parameter mentioned above, the period hould be equal to a T and carrier ignal in a T c PW x, A modulator and in T c T PW x, B modulator hould be hifted with each other by a time =. 4

6 Stability iue of a controlled current ource One of the mot important apect of the current modulator work i it tability. Thi analyi will include an important factor that occur in the operation of a real ytem, which uually i not repected. Thi i an aliaing phenomenon characteritic for ampled-data ytem. The mathematical model of a control ytem of a multi-channel converter for the tability analyi ha been propoed e.g. in [10]. Thi decription i baed on the extenion of Whittaker-Kotelnikov-Shannon (WKS) ampling theory the Generalized Sampling Expanion (GSE) being formulated by Papouli [11]. Aume ignal x t L, the pace of quare-integrable function, where real number domain, and it Fourier tranform X j exit. Aume alo that ampling of x t i uniform and ideal (i.e. with utilization of Dirac erie π y t i the ignal at δ t nt : T, where T i the ampling period) and n AX output of a ample-and-hold amplifier (SHA) a an 0-order extrapolator of a ampled ignal. The relationhip between and apart a tatic (time invariant) X j π component, alo contain a dynamic (time variant) component X j n, o n T the formal tranfer function of the SHA doe not exit. The dynamic component i alo related to the aliaing effect, by which the high frequency pole are folded back into lower frequencie. Although repecting the tatic part only of equivalent tranfer function of SHA give, in mot cae of the ytem tability analyi, atifying reult, the crucial knowledge i that the aliaing mechanim can caue lo of tabilization at critical frequencie [10,1,13,15]. From the point of view of the GSE, general etting i that a ignal Y j xt i proceed by a linear multi-dimenional ampling ytem (SS). Suppoe now that i a common input to ampling ytem and each individual ampling ytem i a ub-ytem of the SS Fig. 4. xt Fig. 4. SS with a ingle ZOH block a a ignal extrapolator (E) at the output. Each ub-ytem ample at a rate of T individual delay i i : i 0,1,..., 1 x * t 1, the t by uing the invere Fourier tranform formula: time of the Nyquit rate. Auming x can be retrieved from it ample

7 (4) x t 1 AX 1 n i0 x n i T AX AX e j t n i T d The overall ampling rate till atifie the Nyquit criterion [11]. The SS, being the conequence of GSE, make it poible to reduce the required ampling frequency to 1, comparing to one-dimenional ampling ytem (WKS ampling theorem), working at the ame ampling rate. Conidering the ytem from the other ide, when it ampling at a rate of 1 T it effective ampling rate i equal to T. A Nyquit band i now -time extended. In the cae of a control ytem of a real multi-channel converter an eential difference in relation to GSE aumption appear. It conit in the fact that each individual converter channel include a ingle SHA and individual channel output ignal are ummed at the output of the converter. Thi modification of the original GSE concept i neceary due to the different poition in the ytem of a ignal umming node. The econd reaon reult from the limitation of dynamic parameter of real power electronic device ued in inverter. In other word, witching frequency ha to be limited due to energy lo in tranition tate of power electronic witche. Thu, the VCCS control ytem include now the multidimenional ample-and-hold ytem (SHS) intead of the SS [10]. The propoed mall-ignal (linear) model of the VCCS with the nd order SHS, being the object of further conideration, i hown in Fig. 5. Fig. 5. Small-ignal model of the VCCS baed on a -channel converter. The propoed model i an IO, SISO and LTI one and can be completely decribed in term of a continuou-time ytem with a tranfer function IL j Kj G j. The ytem tability analyi take advantage of U ref j 1 Kalj Nyquit criterion [14]. Hence, a characteritic equation R j 1 Kalj 0 of the model, repecting (4), take the following form: (5) Rj 1 r k N AX CT 0 nn AX KHS j n n L L j E L R L 0

8 K HS j where: ignal, r CT frequency and N AX 1 a tatic component in a relationhip of the SHS input and output the gain factor of CT, N AX k 0 gain of the regulator, π T a ampling i a number of repected aliae. The function (7) poee ingular point at the frequency n Reearch of the VCCS mall-ignal model have defined the tatic component in the relationhip of input and output ignal of the SHS a follow:. T Sa e T T Sa e T j (6) K (j) Sa coat HS T j : 1 e T j : :, a a T 1 1, 4 4 The Nyquit diagram for the general form of the equation (5) i.e. R j 1 K j, repecting (8), i hown in Fig. 6. It concern the following al exemplary parameter of the mall-ignal model: T =50 μ and in with the period of π n, T L L =5 mh, r CT =1 V/A, L k 0 =10. Since the general form of the equation (5) i a periodic function T π T. n 1 : NAX n NAX E R L =0,, the (P,Q) diagram i alo periodic in interval Fig. 6. Nyquit diagram for the characteritic equation of the mall-ignal model of the VCCS while = and a =var.

9 For the mentioned-above hypothetical model parameter and exemplary cae of the a factor: 0.10, 0.15, 0.0 and 0.5, the (P,Q) phae curve encircle the Nyquit point on the right ide indicating that the ytem i table. The characteritic effect of the nd order ampling i decreaing gain of the SHS while frequencie are cloe to the Nyquit frequency. The gain minimizing effect i maximal wherea ampling i orthogonal (i.e. a =1/4) [10]. It i very intereting and crucial for further utilization of multi-channel inverter concept to determine the maximal regulator gain ( ) to make the ytem table. In order to determine thi value it i neceary to determine amplitude of phae value arg al j π k 0 K al j for the critical K. It occur for the frequency π π, n n 1 : n 0, 1,,.... Having olved the equation (5), the maximal regulator T gain can be expreed by the following formula: (7) where L L E L. L k 0,AX L : 1, a 0 r CTT L : a 1/ 4 rctt The maximal theoretical value of the regulator gain occur in the cae of = and a =1/4. It i -time over the gain of the regulator in cae of a one-channel converter. It give higher quality matching a VCCS output current in a reference ignal. Firt of all, thi cae of the VCCS control ytem parameter will be taken into account in the final conideration. The repone of the VCCS mall-ignal model for the quare-wave reference ignal i hown in Fig. 7. The regulator gain i cloe to the maximal value in term of the expreion (7) and model parameter lited earlier. a) b) Fig. 7. Waveform of characteritic ignal the output current i L and the reference voltage u ref in the mall-ignal model of the VCCS while: a) =1 (or: =, a =0), k 0 =95 and b) =, a =1/4, k 0 =190.

10 A it can be oberved, both ytem are cloe to the un-tability boundary but the value of the regulator gain in cae of a two-channel converter i twice over a gain of a tandard converter. Simulation model of the rectifier ytem A complex imulation model of the 3-phae 1-pule diode rectifier ytem with the current modulation in the DC circuit ha been invetigated in detail. The fundamental block of the current modulator i the VCCS baed on a -channel converter. The nd - order SHS ha been ued in the current regulator. In many cae, the reult of the tudy alo relate to the VCCS baed on a one-channel converter for comparion parameter of both ytem. Selected waveform in the imulation model for the target hape (i.e. triangular) of the reference ignal are hown in the following Figure. Thee are alo related to the two cae of an order of the SHS i.e. =1 and =. The PW carrier frequency T c =100 μ, a PW kind i two-ided and aymmetric, the nominal amplitude value of the reference voltage =10 A, and LE,0, A LE,0,B LE,1,A LE,1, B =1. mh. Value of parameter of the imulation model are conitent with parameter of the real ytem, which i decribed in the next ection. A ref,n a) b) Fig. 8. Waveform of the reference voltage u ref, modulator current for the cae of triangular hape of reference ignal and: a) =1, k 0 =40. Alo current in individual channel of the VCCS ( i L,0,A and i C, and the error ignal k 0 =35, b) i L,0,B Amplitude of the reference ignal i equal to the nominal one. =, a =1/4, u err ) are hown Fig. b). In the cae of the two-channel VCCS hape of the modulator current and reference ignal almot coincide, in contrat to the tandard VCCS, where thee ignal clearly differ from each other. For the VCCS in a two-channel verion the firt pule modulation component in the modulator current i at 4 T c frequency, intead of T c and it amplitude i over 3-time lower compared to a one-channel converter. A very adequate and reliable criterion of the quality of a converter output ignal can be the converter control error given by the following equation: uerr uref ufb (8) CTR 100% 100% u u ref ref

11 CTR =5.88 %: CTR =3.63 %: Auming nominal condition of the imulation model work, the value i a follow: =1, =. Thu, in ene of thi criterion a twochannel VCCS make it poible to improve the quality of the output current about 6 % compared to a one-channel VCCS olution. The reearch on the rectifier ytem ha been baed mainly on it imulation model in the ORCAD/PSpice environment. The baic electrical tructure of the model i introduced in Fig. 9. It repect all fundamental feature of an exemplary real ytem, e.g. non-zero power grid impedance, non-zero winding reitance and leakage inductance of power tranformer and the pule tranformer [16]. Alo, witching procee in rectifier diode and in IGBT ued in the inverter, being execution part of the VCCS, are repected. However, the active rectifier (the TRCT block) ha not been taken into conideration. The imulation model ha been powered by 3x30 V, 50 Hz grid. The nominal DC output power of the rectifier ytem ha been et at 6 kw. P DC,n Fig. 9. Rectifier ytem imulation model (the main block) in the ORCAD/PSpice environment. The following Figure i a typical one. It preent power grid current in a tandard 1- pule diode rectifier and, alo, in the introduced rectifier ytem while a current modulator i diabled. In accordance with the lited parameter of the rectifier imulation model and the nominal output power, the THD value for the power grid current (, and i C ) i approx. equal to 1.5 % in a 5 khz band. i A i B

12 Fig. 10. Waveform of power grid current i A, i B and i C in the rectifier imulation model while the output power i equal to nominal one and the current modulator i diabled. In Fig. 11, in contrat to the previou ituation, the current modulator i enabled. In reult, deformation of power grid current are now of an over order le i.e. THD =1.35 % while the output power i equal to the nominal value and THD =.93 % while the output power i equal to the 10% of thi one. a) b) Fig. 11. Waveform of power grid current i A, i B and i C in the rectifier imulation model while the current modulator i enabled and: a) the output power i equal to the nominal value, b) the output power i equal to 10% of the nominal value. The impact of the number of converter channel on the quality of power grid current can be evaluated on the bai of the error. Thi one i related to the difference of a i A ( i B, i C i ) current and it 1 t harmonic imilarly to the converter control error (10). A value of thi error i function of both, the rectifier output power PDC i, f : 1,. The graph of thi function i hown in Fig. 1. Alo, the PDC,n relationhip of i, and i,1 i preented. P DC and :

13 Fig. 1. Curve of i and a reciprocal relationhip of error function while =1 and =. The quality of the power grid current in cae of utilization of the two-channel converter i increaed about % compared to the tandard one, while it average value i approx. equal to 11.8 %. In conequence, power lo in the rectifier ytem (mainly in tranformer) can be reduced by mean of a two-channel converter olution. The next Figure preent pectrum of the power grid voltage ( and ) for two cae of the VCCS olution baed on a one-channel and a two-channel converter. u A u B u C u A u B Fig. 13. Spectrum of the power grid voltage (, = (the blue curve). u C ) while =1 (the red curve) and In the cae of the two-channel VCCS pule modulation component in the input voltage pectrum are hifted at if c : i C frequencie, compared to the one-channel converter. It give minimization of the level of diturbance in the power grid o the current modulator a power electronic converter can meet EC requirement more eaily. Laboratory model of the current modulator Alo, the laboratory model of the part of rectifier ytem ha been invetigated. The aim of the tudy ha been validation of theoretical aumption and reearch reult of the rectifier imulation model mainly in the relation to the quality of the modulator current. The laboratory model ha conited of thee block of the full rectifier circuitry which are on the grey background in Fig. 1. It diagram ha been conitent with Fig. 3. The econdary winding of the pule tranformer ha been hort circuited.

14 Baic technical parameter of the laboratory prototype are given below: DC link voltage in the multi-channel converter: 60 V, nominal amplitude of the modulator current: 10 A, inductance of the ingle choke in the VCCS: mh, ignal ampling frequency in the control module: 0 khz, PW carrier frequency: 10 khz, mode of the PW generator work: double-updated (per the carrier period). Pule tranformer parameter are hown in Fig. 9. Thee have been determined on the bai of meaurement of the real tranformer [16] which ha been implemented in the firt laboratory model of the rectifier ytem [5]. The general view of the laboratory tand i hown in Fig. 14. Fig. 14. General view of the laboratory tand. The control module in the laboratory prototype ha been baed on the ALS-G DSP evaluation board with Analog Device ADSP-1369 SHARC DSP while in the execution block two P FE LABINVERTER have been utilized. Thi family of DSP i equipped with the high performance 16-channel PW generator hence, i epecially dedicated implementation in power electronic device. Alo the LABINVERTER development ytem i deigned for application in a power electronic; it i equipped, among other item, with a 3 leg IP/IGBT. Both of thee ytem are manufactured by ALFINE-TI [17]. In order to oberve and analyze waveform the TEKTRONIX DPO5034B ocillocope ha been ued. Laboratory model tet have been carried out for the current modulator amplitude being in the range of 10 %100 % of the nominal one. Alo, two cae of converter configuration have been teted i.e. =1 and =. In Fig. 15 and 16 elected waveform in the laboratory prototype of the modulator ytem are hown. Fig. 15. Selected waveform in the laboratory prototype of the current modulator: reference voltage, modulator current, and error ignal while =1. The current modulator amplitude i equal to the nominal one.

15 a) b) Fig. 16. Selected waveform in the laboratory prototype of the current modulator: reference voltage, modulator current, error ignal Fig. a), and current in individual channel of the VCCS Fig. b), while =. The current modulator amplitude i equal to the nominal one. Auming nominal condition of the laboratory model work, the value of the control error i a follow: 9.8 %: =1 and 5.9 %: =. Thu, in ene of the control error criterion a two-channel VCCS make it poible to improve the quality of the output current about 66 % compared to a one-channel VCCS olution. Higher (compared to the imulation model) the control error value i caued mainly by error (non-linearity) of current tranducer, which e.g. the total accuracy i equal to 0.65 %. Alo, inductor and pule tranformer baed on ferromagnetic (repectively powdered iron and ilicon teel) core are non-linear. However, in thi cae the relationhip of the control error value i imilar to the cae of the imulation model. In the author opinion it confirm the good quality of the imulation model. CTR CTR Concluion In thi tudy one of the way leading to increaing the quality of power grid current of traditional diode rectifier i preented. In order to obtain thi a current modulator in the common DC circuit of two 6-pule rectifier ha been utilized. The modulator i baed on a wide-band power electronic controlled current ource with a multi-channel converter. The converter control ytem implement aumption of the Papouli Generalized Sampling Expanion theory. Alo, the control algorithm repect aliaing effect, having the influence on the ytem tability, taking place in ampled-data ytem. They make it poible to maximize crucially effective gain of the regulator and, in conequence, better matching of the modulator output current in the reference ignal.

16 A a reult the total THD factor of the power grid current i lowered approx. 11%8%, compared to the tandard converter. It give opportunity of decreaing power loe in the rectifier power grid tranformer. Thank to feature of a multi-channel converter the pectrum of the power grid voltage i more beneficial due to PW component are hifted at the higher frequency zone. The olution of a rectifier i epecially attractive in the cae of a higher power of the receiver, ince power of the current modulator i approx. equal to 3 % of the rectifier DC output power. Thu, higher complexity of the propoed converter olution ha only a minimal effect on the cot of the whole rectifier ytem. Alo, in the nearet future it i planned the full contruction of a laboratory model of the rectifier ytem. It will be done in cooperation with an indutrial partner. Thi model can be treated a an extenion of the current modulator prototype baed on a twochannel converter. Reference 1.. Siwczyńki and. Jaraczewki, Reactive compenator ynthei in timedomain, BULLETIN OF THE POLISH ACADEY OF SCIENCES TECHNICAL SCIENCES, Vol. 60, No. 1, (01)... Gwóźdź, Power Electronic Active Shunt Filter with Controlled Dynamic, Proc. of COPEL: The International Journal for Computation and athematic in Electrical and Electronic Engineering, Vol. 3, No. 4, (013). 3.. Jaińki, P. Antoniewicz and. P. Kaźmierkowki, Induction otor Drive fed by PW Rectifier/Inverter with Victor Control (in Polih), Przegląd Elektrotechniczny, No 6/005, 1-5 (005). 4. P. yiak and R. Strzelecki, A robut 18-pule diode rectifier with coupled reactor, BULLETIN OF THE POLISH ACADEY OF SCIENCES TECHNICAL SCIENCES, Vol. 59, No. 4, (011). 5.. Krytkowiak, Power rectifier ytem with improved rate with power electronic current modulator (in polih), Doctoral thei, Poznan Univerity of Technology, Faculty of Electrical Engineering, Poznań (009). 6. R. Strzelecki and H. Supronowi c z, The power factor of AC circuit and correction method (in polih), OWPW, Warzawa, (000). 7.. Gwóźdź, Analyi of work of wide-band power electronic converter (in polih), Przegląd Elektrotechniczny, No 1, 16-1 (010). 8. S. Huth, DC/DC converter in Parallel Operation with digital load ditribution control, Proceeding of the IEEE International Sympoium on Indutrial Electronic, Vol., (1996). 9. L. Aiminoaei, E. Aeloiza, P.N. Enjeti, and F. Blaabjerg, Shunt Active-Power-Filter Topology Baed on Parallel Interleaved Inverter, IEEE TRANSACTIONS ON INDUSTRIAL ELECTRONICS, Vol. 55, No. 3, (008) Gwóźdź, Stability of Dicrete Time Sytem on Bae Generalized Sampling Expanion, Kwartalnik Elektryka, Politechnika Śląka, Vol. 1 (17), Gliwice, 9-40 (011). 11. A. Papouli, Generalized Sampling Expanion, Proceeding of the IEEE Tranaction on Circuit and Sytem, Vol. 4, Iue 11, (1977). 1. L. irkin and Z. J. Palmor, Control Iue in Sytem with Loop Delay, The Handbook of Networked and Embedded Control Sytem (D. Hritu-Varakeli and W. S. Levine, ed.), Birkhäuer, (005). 13. G. einma and L. irkin, Sampling from a Sytem-Theoretic Viewpoint: Part I Concept and Tool, Part II Noncaual Solution, IEEE Tran. On Signal Proceing, Vol. 58, No. 7, pp (010).

17 14. T. Kaczorek, Control and ytem theory (in polih), Wyd. Naukowe PWN, W-wa, Gwóźdź, Impact of Aliaing Effect on Work of Wide Band Power Electronic Current Source, XIX Sympoium Electromagnetic Phenomena in Nonlinear Circuit, aribor, Słowenia, (006) Krytkowiak and. Gwóźdź, Calculation of Parameter of Equivalent Circuit of Pule Tranformer, XX Sympoium Electromagnetic Phenomena in Nonlinear Circuit, Lille, France, (008). 17. Product page of ALFINE-TI: [acceed: ]. Autorzy: dr hab. inż. ichał Gwóźdź, dr inż. ichał Krytkowiak; Intytut Elektrotechniki i Elektroniki Przemyłowej, Zakład Energoelektroniki i Sterowania, Wydział Elektryczny, Politechnika Poznańka, ul. Piotrowo 3a 37, Poznań, ichal.gwozdz@put.poznan.pl, ichal.krytkowiak@put.poznan.pl.