Performance Evaluation of a Novel Hybrid Multipulse...

3030 IEEE TRANSACTIONS ON INDUSTRIAL ELECTRONICS, VOL. 54, NO. 6, DECEMBER 2007

Performance Evaluation of a Novel HybridMultipulse Rectifier for Utility Interface

of Power Electronic ConvertersLuiz Carlos Gomes de Freitas, Marcelo Godoy Simões, Senior Member, IEEE,

Carlos Alberto Canesin, Member, IEEE, and Luiz Carlos de Freitas

Abstract—This paper presents an improved analysis of a novelProgrammable Power-factor-corrected-Based Hybrid MultipulsePower Rectifier (PFC-HMPR) for utility interface of power elec-tronic converters. The proposed hybrid multipulse rectifier is com-posed of an ordinary three-phase six-pulse diode-bridge rectifier(Graetz bridge) with a parallel connection of single-phase switchedconverters in each three-phase rectifier leg. In this paper, the au-thors present a complete discussion about the controlled rectifiers’power contribution and also a complete analysis concerning thetotal harmonic distortion of current that can be achieved when theproposed converter operates as a conventional 12-pulse rectifier.The mathematical analysis presented in this paper corroborate,with detailed equations, the experimental results of two 6-kWprototypes implemented in a laboratory.

Index Terms—AC motor drives, high power drives for trolley-bus systems, high power factor three-phase rectifiers, multipulserectifiers, tractions applications, 12-pulse rectifiers.

I. INTRODUCTION

D IODE-BRIDGE rectifiers are very important for severalindustrial and home equipment in order to feed the inter-

mediate dc link usually used in electronic topologies. However,ordinary diode-bridge rectifiers do not meet harmonic-contentrestrictions as imposed by IEC61000-3-4 [1]–[3]. Therefore,complex power-factor correction structures or expensive bulkylinear filters must be installed to compensate for such harmoniccontamination. There has been tremendous interest in achiev-ing a low harmonic distortion in ac–dc converters throughprogrammable power-factor front-end rectifiers or some othertechniques [4], [5].

The current state of art suggests the application of multi-pulse converters for achieving cancellation of input harmoniccurrent at the need of magnetic circuits such as phase-shiftingtransformers, interphase transformers (IPTs), current-balancing

Manuscript received March 8, 2007; revised July 31, 2007. This work wassupported by CAPES, FAPEMIG, CNPq, FAPESP, and the National ScienceFoundation.

L. C. G. de Freitas is with the Industry Division, Federal Center of Tech-nological Education of Goiás (CEFET-GO/UnED-Jataí), Jataí, GO 75804020,Brazil (e-mail: [email protected]).

M. G. Simões is with the Engineering Division, Colorado School of Mines(CSM), Golden, CO 80401-1887 USA (e-mail: [email protected]).

C. A. Canesin is with the Faculty of Engineering, São Paulo State Univer-sity (UNESP), Ilha Solteira, SP 15385-000, Brazil (e-mail: [email protected]).

L. C. de Freitas is with the Faculty of Electrical Engineering (FEELT),Federal University of Uberlandia (UFU), Uberlandia, MG 38400-902, Brazil(e-mail: [email protected]).

Digital Object Identifier 10.1109/TIE.2007.907004

transformers, and harmonic-blocking transformers with the ob-vious drawback of the complex design of heavy, bulky, andexpensive custom-made equipment [4]–[13].

Elimination of IPTs is particularly desirable when there arepreexisting harmonic voltages in the three-phase power source.This is because preexisting harmonic voltages cause changes inthe dc output voltage, which greatly complicates the design ofIPTs [4], [14]. Therefore, many authors have presented greatworks focusing on the development of transformer concepts formultipulse-rectifier applications in order to improve the currentsharing between two rectifiers’ bridges and/or to eliminate thenecessity of IPTs [4], [5], [7], [9], [10], [12], [13]. However,despite the robustness of these structures, the volume, weight,and size are still limiting factors.

Hence, there has been great interest in achieving autotrans-former arrangements to be used in rectifier applications inorder to reduce the volume, weight, and size of the multipulse-rectifier structures [4], [5], [7], [13], [15]–[17]. It must beemphasized that, in some cases, since autotransformers are usedto feed noncontrolled rectifiers, IPTs become an essential ele-ment in order to assure the correct operation of the multipulse-rectifier structure.

An alternative technique that provides the correct operationof multipulse rectifier fed through an autotransformer withoutusing IPTs consists of the connection of switched converters inthe dc side of each three-phase diode-bridge rectifier in order toguarantee the correct current sharing among the rectifier units.For example, in a 12-pulse rectifier, there will be two switchedconverters rated at 50% of the total output power, or in an18-pulse rectifier, there will be three switched converters ratedat 33% of the total output power, and so on. However, in high-power levels (up to 50 kW), the efficiency and circuit complex-ities of the switched converters become an another challenge toovercome in the field of multipulse rectifiers [10], [18].

On the other hand, a novel approach that overcomes manydisadvantages in the field of multipulse rectifiers is presentedand fully evaluated in this paper [19], [20]. The proposed struc-ture was obtained, associating a switched converter in parallelwith each leg of a three-phase six-pulse diode rectifier result-ing in a programmable input-line current waveform structure,which is shown in Fig. 1. The system is capable of providingultraclean power without the need of phase-shifting trans-formers, IPTs, current-balancing transformers, or harmonic-blocking transformers, and it was named ProgrammablePFC-Based Hybrid Multipulse Power Rectifier (PFC-HMPR).

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Fig. 1. Simplified diagram of the PFC-HMPR.

The power rating of the parallel converters (Rect-2) is afraction of the total output power, varying from 20% to around45% of the rated power, depending on the desired THDI thatmust be achieved. It will be fully demonstrated in this paper.

The proposed hybrid multipulse rectifier is a structure thatcombines the robustness, simplicity, and reliability of the six-pulse diode-bridge rectifier with the high-frequency operationof the controlled rectifiers, and therefore, the volume, weight,and size of the proposed structure are extremely reduced withhigher efficiency. Thus, the rated power can be increasedup to 50 kW, which cannot be achieved with ordinary unitpower-factor three-phase pulsewidth-modulation (PWM) recti-fiers [22]–[24].

Thus, this paper presents a performance evaluation of theproposed PFC-HMPR operating as a 12-pulse rectifier, includ-ing a mathematical analysis that corroborates the experimentalresults of the two prototypes rated at 6 kW.

II. PRINCIPLE OF OPERATION

From the combination of the input-line currents of Rect-1(current ia1) and Rect-2 (current ia2), the input-line current ofthe proposed PFC-HMPR (current ia(in)) is obtained (line A forinstance). Hence

ia(in)(t) = ia1(t) + ia2(t) (1)

ib(in)(t) = ib1(t) + ib2(t) (2)

ic(in)(t) = ic1(t) + ic2(t) (3)

whereia(in)(t), ib(in)(t), ic(in)(t) ac input-line currents of

PFC-HMPR;ia1(t), ib1(t), ic1(t) ac input-line currents of Rect-1;ia2(t), ib2(t), ic2(t) ac input-line currents of Rect-2.

Fig. 2. Theoretical waveforms—12-pulse composition.

Fig. 2 shows the principle of constructing an input-line cur-rent ia(in) through two components ia1 and ia2 that are obtainedwhen the PFC-HMPR topology operates as a conventionalthree-phase 12-pulse rectifier. The ia2 current waveform is themain controller of the overall characteristic of the ia(in) wave-form; therefore, the PFC-HMPR allows the improvement of theinput-line current total harmonic distortion (THD) through avery simple technique.

In order to achieve the same operational characteristics ofa conventional 12-pulse rectifier, which means to provide anac input-line current with harmonic components of 12n ± 1orders, the peak value of current ia2 (I2P) must be propor-tional to the peak value of current ia1 (I1P), as demonstratedin Section III. In this case, the switched converters’ power



Fig. 3. Theoretical waveforms—Sinusoidal composition.

contribution will be around 20% of the total output power(6.67% for each switched converter).

Concerning the operational characteristics of the proposedPFC-HMPR, it is also important to emphasize that theswitched-converter-imposed current can assume any waveform,depending on the final ac input-line current waveform that is de-sired. This operational characteristic assures higher flexibility,which means that a sinusoidal input-line current waveform [21]can be achieved, providing THDI as low as it can be achievedin 24-pulse rectifiers [12].

In this context, the current ia2 can be imposed, as shown inFig. 3. Therefore, the combination of the currents ia1 and ia2

results in a sinusoidal input-line current just as ordinary unitpower-factor three-phase PWM rectifiers can provide; however,complex control strategies, which contribute to increase its costand implementation difficulties, are not needed [22]–[24].

In conclusion, the lower is the desired THDI , and the higheris the switched converters’ power contribution. Thus, in theextreme, in order to achieve a sinusoidal input-line current, theswitched converters’ power contribution will be around 45% ofthe total output power (15% for each switched converter), asdemonstrated in [21].

The design of the switched converters can be optimized inorder to mitigate its power contribution and, at the same time, toachieve the desired THDI assuring higher overall efficiency. Itis important to emphasize that the switched converters (Rect-2)provide active power to the load; hence, the proposed structurecannot be classified as static compensators, which makes thisproposal unique.

III. HARMONIC ANALYSIS OF THE 12-PULSE

INPUT-LINE CURRENT

In order to reduce the THDI , the PFC-HMPR is capableof operating with 12-pulse or sinusoidal ac currents. When

operating with sinusoidal input-line current, the PFC-HMPRpresents its better performance related to the THDI , meetingall harmonic-content restrictions imposed by IEC61000-3-4;hence, a harmonic analysis of the input-line current waveformis not needed. However, when operating as a 12-pulse rectifier,this kind of analysis is necessary since the elimination ofharmonic components such as the 5th, 7th, 17th, and 19thdepends on the peak value of the switched converters’ input-line currents ia2, ib2, and ic2.

Since the input currents of Rect-1 and Rect-2 are continuousfunctions that repeat periodically, therefore, using the Fouriertheorem, it is possible to prove that the PFC-HMPR input-linecurrent presents the same harmonic spectrum of a conventional12-pulse rectifier (12n ± 1). As it is well known, the frequencydomain representation of current ia1 is given by

ia1(ωt) =2√

3π

I1P

[cos(ωt)− 1

5cos(5ωt)+

17

cos(7ωt)

− 111

cos(11ωt)+113

cos(13ωt)

− 117

cos(17ωt)+119

cos(19ωt)

− 123

cos(23ωt)+125

cos(25ωt)+· · ·].

(4)

The frequency-domain representation of current ia2 is given by

ia2(ωt) =4π

(kI1P)

[0.63

∞∑n=1,13,25,...

1n

cos(nωt)

+ 2.36∞∑

n=5,17,...

1n

cos(nωt)

− 2.36∞∑

n=7,19,...

1n

cos(nωt)

− 0.63∞∑

n=11,23,...

1n

cos(nωt)

]. (5)

A. Harmonic Components of the PFC-HMPRInput-Line Current—ia(in)

Using Matlab software, it was possible to obtain the time-domain representation of current ia(in), which is obtained fromthe combination of (4) and (5). Thus, it is shown in Fig. 4 thewaveform of current ia(in) taking into account the harmoniccomponents of order n = 200.

B. Total Harmonic Distortion of the AC Input Current—ia(in)

In order to illustrate the PFC-HMPR performance relatedto the THDI achieved when a 12-pulse current is imposed inthe ac system, the Matlab software was used to calculate thefinal THDI of the input-line current as a function of k. Thus,in Fig. 5, one can observe that the minimum THDI (around13.4%) is achieved when the peak value of current ia2 is around



Fig. 4. Waveform of current ia(in) obtained through the Fourier of currentsia1 and ia2.

Fig. 5. Total harmonic distortion of the input-line current for different valuesof k—12-pulse mode of operation.

33% of the peak value of current ia1 (k = 1/3). It is importantto emphasize that this value of THDI is the same result reportedin [10] and [15] where it was obtained with an 18-pulse rectifierscheme with an autotransformer feeding three six-pulse dioderectifiers with common load.

In conclusion, in order to prove that the input-line currentof the PFC-HMPR, operating as an ordinary 12-pulse rectifier,presents the harmonic components of order 12n ± 1, the Matlabsoftware was used to combine (4) and (5) obtaining the valuesshown in Fig. 6.

As one can see that, when k is around 1/3, the 5th, 7th, 17th,and 19th harmonics assume extremely reduced levels; hence, itcan be stated that, in this mode of operation, the PFC-HMPRinput-line current is given by

ia(in)(ωt) =4.3I1P

π

[cos(ωt) −

∞∑n=11,23,35,...

1n

cos(nωt)

+∞∑

n=35,25,37,...

1n

cos(nωt)

]. (6)

Fig. 6. Harmonic spectrum of the PFC-HMPR input-line current operating asa 12-pulse rectifier for 0.3 ≤ k ≤ 0.36.

IV. CHOICE OF THE SWITCHED CONVERTERS

Boost converters have been traditionally used as front-endwave-shaping systems, but, in order to be applied as a parallelpath of three-phase six-pulse diode-bridge rectifier, noniso-lated boost converters are not suitable. It means that boostconverters fed through line voltages or line-to-neutral volt-ages are not suitable to be used in the proposed PFC-HMPRstructure.

When boost converters are fed through a line-to-line voltage,it is observed that, during the period of time when the input-linevoltage of the three-phase power source is higher than the dcoutput voltage, the boost current keeps on increasing even whenthe switch is open. In fact, when the boost switch is open andthe freewheeling diode is forward-biased connecting the pathbetween Rect-2 and Rect-1, the boost current flows throughthe diodes of the three-phase six-pulse rectifier bridge (Rect-1),and its control is lost, eventually impeding the desired current-waveform composition.

On the other hand, when boost converters are fed through aline-to-neutral voltage, it can be assured that the input voltagewill never be higher than the dc output voltage; however, theboost current still finds a path through the negative diodes’group of the three-phase six-pulse rectifier bridge (Rect-1)instead of returning through the boost circuit. It was observedeven when modified boost converters were used [22].

In this context, single-ended primary inductor converter(SEPIC) behaves naturally as an input-current source, allowingthe waveform of the input current to be imposed with a suitablecontrol strategy. In contrast to the boost-converter behavior,when the switch Sn is opened (n: 1, 2, 3), the series capacitorof the SEPIC converter assures, at any operating conditions, theisolation of those circuits and the correspondent decrease of thecurrent flow through the input inductor. Thus, the imposition ofthe input current does not strongly depend on the level of the dcoutput voltage V0 (dc link voltage).

In order to improve the SEPIC converters’ performance,some modifications were made, as one can observe in Fig. 7.Each circuit differs from the normal SEPIC topology by thepresence of a split input inductor, a split capacitor, and a splitfreewheeling diode. These modifications are necessary on theaccount of circulating currents that exist among the SEPICconverters when operating with a common load. The purposeof these modifications is to avoid the circulating currents as-suring the correct ac current composition. A very similar case



Fig. 7. Proposed PFC-HMPR deploying modified SEPIC converters.

concerning parallel connection of boost converters was reportedin [22].

It should be emphasized that, when boost converters are fedthrough single-phase transformers, there is a galvanic isolation,as shown in Fig. 3. In this arrangement, the boost current isconfined to the secondary winding circuit, and the dc outputvoltage is kept with an average value approximately equal tothe peak line-voltage value. This structure is able to replace theSEPIC converters because it can be assured that the boost cur-rent will be forced to return through the boost circuit instead ofthe three-phase six-pulse rectifier bridge. Hence, the control ofthe boost current is no longer lost, resulting to the achievementof the desired input-line current waveform.

As a result, the proposed concept can also be implemented,deploying boost converters, but with the obvious drawback ofrequiring extra magnetic devices, which increases the volume,weight, and cost of the structure. The proposed PFC-HMPRdeploying boost converters is shown in Fig. 8.

It is important to emphasize that, even when using single-phase isolating transformers, the proposed PFC-HMPR deploy-ing boost converters can still be attractive when compared toother multipulse-rectifier structures [7], [18] since each single-phase isolating transformer must be rated at 7% (12-pulse acinput current) of the total output active power, as described inSection VI, or 15% (sinusoidal ac input current), as reportedin [21]. Fig. 8. Proposed PFC-HMPR deploying boost converters.



V. SWITCHED CONVERTERS’ POWER

CONTRIBUTION—12-PULSE AC CURRENT

The rated power processed by each rectifier group(Rect-1 and Rect-2) can be determined based on the peak valueof the input-line currents ia1 and ia2, respectively (phase A forinstance). In this context, the target is to quantify the fraction ofpower processed by each rectifier group in relation to the totaloutput power. The system is going to be considered as loss-freeand with unity input power factor. Thus

P0 = Pin =32VPIP (7)

whereP0 total output active power;Pin total input active power;VP peak value of the line-to-neutral voltage;IP peak value of the input-line current.The power processed by each dc–dc converter (Rect-2), when

the proposed PFC-HMPR operates as a 12-pulse rectifier, canbe determined as follows:

PDC−DC Conv.1 =1π

[ π/6∫0

VP sin(ωt) · I2Pdωt

+

2π/3∫π/3


+

π∫5π/6


](8)

where I2P is the peak value of the switched-converter input-linecurrent.

As it was demonstrated in the last section, the switched-converter-imposed current must be proportional to the six-pulse diode-bridge-rectifier input current in order to achieve thelowest THDI ; thus, the peak value of the switched-converterinput-line current is expressed by

I2P = k · I1P (9)

whereI1P peak value of the six-pulse diode-bridge-rectifier

input-line current;k constant.Therefore, the switched-converters’ power contribution is

given by

PRect-2 = 3 · VP · IP ·(

1.268π

). (10)

The power rating of the switched converters (PRect−2) inrelation to the total output power (P0) can be determined as

PRect-2P0

=3 · VP · IP ·

(1.268

π

)3/2 · VP · IP

. (11)

Fig. 9. Representation of the PFC-HMPR performance concerning theswitched converters’ power contribution—12-pulse ac current.

Since the peak value of the input-line current is

IP = I1P + I2P = I1P(k + 1). (12)

the power contribution of the switched converters can beexpressed as

PRect-2P0

= 2.536[

k

π · (k + 1)

]. (13)

Provided that the switched converters operate as currentsources with a suitable imposed current and that the rated powerprocessed by each one is determined based on the peak value ofthe imposed input-line currents (ia2, ib2, and ic2), the powerrating of Rect-1 is given by

PRect-1 = P0 − PRect-2. (14)

In order to prove the accuracy of (13) and (14), the Matlabsoftware was used to illustrate the performance of each rectifiergroup (Rect-1 and Rect-2). Thus, one can observe in Fig. 9that, when operating as an ordinary 12-pulse rectifier, for0.33 ≤ k ≤ 0.36, the power contribution of Rect-2 is around20% of the total output power (6.67% for each switchedconverter).

As one can observe, the operation regions for 0.3 ≤ k ≤ 0.36maximize the six-pulse diode-bridge-rectifier power contribu-tion and minimize the switched converters’ power contribution.The other operation regions must be avoided so that the lowestTHDI and the minimum switched converters’ power contribu-tion can be assured.

VI. EXPERIMENTAL ANALYSIS—PFC-HMPROPERATING AS A 12-PULSE RECTIFIER

A. Control Strategy

The experimental setup was built using analog gate circuitry.Fig. 10 shows a simplified block diagram of the electroniccircuit used in the experimental setup.

As one can observe, a sample of the input line-to-neutralvoltage is rectified and compared with two dc voltage levels



Fig. 10. Simplified diagram block of the PWM control strategy in closed loop—12-pulse ac current.

TABLE IPROTOTYPE PARAMETERS—PFC-HMPR—12-PULSE AC CURRENT

for the pulse generator circuit. The output of the comparators isconnected to an OR gate, resulting to a pulsed output voltagewith a width equal to π/3 and an amplitude equal to thecomparator supply voltage.

Therefore, the reference current signal is filtered and reducedto unity value in order to be applied to the input of the

TABLE IISUMMARY OF EXPERIMENTAL RESULTS OF THE

PFC-HMPR—12-PULSE AC CURRENT



Fig. 11. (a) Prototype of the PFC-HMPR deploying modified SEPIC converters. (b) Modified SEPIC converters.

Fig. 12. Main experimental results of the PFC-HMPR—operating as a 12-pulse rectifier—deploying modified SEPIC converters. (a) Input-line current ofRect-1/Phase A. (b) Input-line current of Rect-2/Phase A. (c) Input-line current and line-to-neutral voltage of PFC-HMPR/Phase A. (d) Input-line currents ofPFC-HMPR.

signal-multiplier circuit. The signal-multiplier circuit also re-ceives a current signal of the six-pulse diode-bridge rectifier(IRect-1) in order to generate a signal proportional to 1/3 of thecurrent IRect-1. As a result, the reference current signal to beimposed at the switched converters is obtained at the output ofthe multiplier circuit.

Finally, the PWM reference generator circuit receives the sig-nal from the multiplier circuit and, with a sawtooth waveform,provides the PWM reference current signal that is comparedwith the current through the input inductor of the switched con-verters. Therefore, the driving command to the main switchedconverters’ switch is provided through the gate-drive circuit.

B. Experimental Results

After a careful simulation study using PSpice, two 6-kWprototypes of the proposed PFC-HMPR were built and ana-lyzed in a laboratory. The PFC-HMPR has been implemented,deploying modified SEPIC converters and boost convertersfed through isolating transformers. The parameters set for theprototypes are presented in Table I.

The harmonic content of the input-line currents and inputvoltages, the input power factor, the displacement factor, thetrue power, the reactive power, and the apparent power for eachphase are presented in Table II. These results were obtained



Fig. 13. (a) Ch.1, dc link voltage (V0); Ch.2, current through the resistive load (I0); Ch.M, average output power of PFC-HMPR (P0). (b) Ch.1, rectified inputvoltage of Rect-2 (VDC); Ch.2, rectified input current of Rect-2 (IL); Ch.M, average input power of Rect-2.

using the Tektronix Software Solutions: WSTRO & WSTROUWaveStar Software for Oscilloscopes/Trial Version.

It is important to outline that, when operating as an ordinary12-pulse rectifier, the THDI achieved was less than 14% inboth prototypes, as expected and demonstrated in Section II.Moreover, the switched converters’ power contribution in bothprototypes was less than 20%. The first prototype built in alaboratory is shown in Fig. 11(a) and (b), where one can observethe modified SEPIC rectifiers in detail.

In order to illustrate the performance of the proposed PFC-HMPR, the experimental results are presented in the followingfigures.

In Fig. 12(a) shows the ac input current of the uncontrolledsix-pulse rectifier (Rect-1), and in Fig. 12(b) shows the ac inputcurrent of the modified SEPIC converter connected to line A.

In Fig. 12(c), the input-line current ia(in) is shown togetherwith the line-to-neutral voltage va. It is important to emphasizethat the current ia(in) is the result of the combination of currentsia1 and ia2 (ia(in) = ia1 + ia2).

The input-line currents ia(in), ib(in), and ic(in) are shown inFig. 12(d). These signals were acquired using a two-channeloscilloscope, and all signals shown in Fig. 12(d) were acquiredwith the trigger level set to channel 1 (voltage va).

The average input power of the uncontrolled six-pulse recti-fier is shown in Fig. 13(a), and the average load power is shownin Fig. 13(b).

The frequency spectrum of the input-line currents is shownin Fig. 14 and compared with the harmonic-content restrictionsimposed by IEC61000-3-4.

Analyzing the frequency spectrum of the input-line currentsshown in Fig. 14, one can observe that the significant harmoniccomponents are the 11th, 13th, 23th, and 25th, as expected.

The second prototype built in a laboratory is shown inFig. 15(a) and (b), where one can observe the boost convertersin detail.

It must be observed that the power rating of the low-frequency single-phase isolating transformers available in alaboratory is much higher than the power rating processedby each boost converter and that, being so, the size of thecontrolled rectifiers deploying boost converters can be ex-tremely reduced with a specific transformer designed for thisapplication.

Fig. 14. Frequency spectrum of the PFC-HMPR input-line currents—operating as a 12-pulse rectifier—deploying modified SEPIC converters.(a) Line A. (b) Line B. (c) Line C.



Fig. 15. (a) Prototype of the PFC-HMPR deploying boost converters. (b) Boost converters.

Fig. 16. Main experimental results of the PFC-HMPR—operating as a 12-pulse rectifier—deploying boost converters. (a) Input-line current of Rect-1/Phase A.(b) Input-line current of Rect-2/Phase A. (c) Input-line current and line-to-neutral voltage of PFC-HMPR/Phase A. (d) Input-line currents of PFC-HMPR.

Fig. 17. (a) Ch.1, dc-link voltage (V0); Ch.2, current through the resistive load (I0); Ch.M, average output power of PFC-HMPR (P0). (b) Ch.1, rectified inputvoltage of Rect-2 (VDC); Ch.2, rectified input current of Rect-2 (IL); Ch.M, average input power of Rect-2.



Fig. 18. Frequency spectrum of the PFC-HMPR input-line currents—operating as a 12-pulse rectifier—deploying boost converters. (a) Line A.(b) Line B. (c) Line C.

The experimental results shown in Figs. 16–18 corroboratethe analyzed theoretical results.

Fig. 16(a) and (b) shows the input-line currents of thesix-pulse diode-bridge rectifier and the boost converter, re-spectively. These currents are responsible in performing the12-pulse waveform in the input-line current. The experimentalinput-line current is shown in Fig. 16(c) and (d), providingconditions to obtain a low THDI value as expected.

The average input power of the uncontrolled six-pulse recti-fier is shown in Fig. 17(a), and the average load power is shownin Fig. 17(b).

The frequency spectrum of the PFC-HMPR input-line cur-rents, deploying boost converters, is shown in Fig. 18 and

compared with the harmonic-content restrictions imposed byIEC61000-3-4.

In Table II, a summary of the PFC-HMPR experimentalresults is given.

VII. CONCLUSION

This paper has shown the analysis, design, and evaluation ofa novel hybrid power rectifier capable of achieving a near-unitypower factor. The system consisted of single-phase switchedconverters connected to every leg of an ordinary six-pulsediode-bridge rectifier. Such structure allowed a programmableinput-line current.

The parallel converters’ power rating was a fraction of thetotal output power and depended on the desirable total har-monic distortion of the input-line current (THDI). To impose a12-pulse standard, less than 20% of the rated output poweris processed by the switched converters. Thus, this proposedstructure is recommended for high-power installations.

The proposed structure provided a multipulse ac cur-rent without using phase-shifting transformers, interphasetransformers, current-balancing transformers, and harmonic-blocking transformers, providing a simplified design and areduced cost.

In addition to the converter analysis, experimental results ofthe two 6-kW systems were found to corroborate the proposedconcept, the mathematical analysis, and the control strategy.

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Luiz Carlos Gomes de Freitas received the B.S.,M.S., and Ph.D. degrees in electrical engineer-ing from the Federal University of Uberlandia,Uberlandia, Brazil, in 2001, 2003, and 2006,respectively.

He is currently with the Industry Division, Fed-eral Center of Technological Education of Goiás(CEFET-GO/UnED-Jataí), Jataí, Brazil, where hehas been working to establish research and educa-tion activities in the industry application of powerelectronic converters. His research interests include

high-frequency power conversion, active power-factor correction techniques,multipulse rectifiers, and clean-power applications.

Marcelo Godoy Simões (S’89–M’95–SM’98) re-ceived the B.Sc. and M.Sc. degrees from the Uni-versity of São Paulo, Guaratinguetá, Brazil, in 1985and 1990, respectively, and the Ph.D. degree fromThe University of Tennessee, Knoxville, in 1995. In1998, he received the D.Sc. degree (Livre-Docência)from the University of São Paulo.

He was a Faculty Member with the University ofSão Paulo from 1989 to 2000. Since 2000, he hasbeen with the Colorado School of Mines, Golden,and has been working on the research of fuzzy logic

and neural networks applications to power electronics, drives, and machinescontrol. He was a Visiting Professor with the University of Technologyof Belfort-Montbéliard, Belfort, France. He published the first book in thePortuguese language about fuzzy modeling. He published two pioneeringbooks, one with CRC Press on the application of induction generators forrenewable energy systems and the other with Wiley/IEEE on the integrationof alternative sources of energy.

Dr. Simões is a recipient of the National Science Foundation (NSF)–FacultyEarly Career Development (CAREER) Award. This is the NSF’s most pres-tigious award for new faculty members, recognizing activities of teacherscholars who are considered most likely to become the academic leaders of the21st century. He served IEEE in various capacities. Currently, he is the Vice-Chair for IEEE IAS Industry Automation and Control Committee and anAssociate Editor for the IEEE TRANSACTIONS ON POWER ELECTRONICS.

Carlos Alberto Canesin (S’87–M’97) receivedthe B.S. degree in electrical engineering from theSão Paulo State University (UNESP), Ilha Solteira,Brazil, in 1984, and the M.S. and Ph.D. degrees inelectrical engineering from the Federal University ofSanta Catarina, Florianópolis, Brazil, in 1990 and1996, respectively.

From June 1985 to early 1990, he was an Aux-iliary Professor with the Department of ElectricalEngineering (DEE), Faculdade de Engenharia de IlhaSolteira (FEIS), UNESP, and became an Assistant

Professor in September 1990. From December 1996 to December 1998, hewas an Assistant Ph.D. Professor with the DEE, FEIS, UNESP, where hebecame an Associate Professor in December 1998 and is currently an AssociatePh.D. Professor. He started the Power Electronics Laboratory, UNESP. He is aResearch Engineer with the National Council of Technological and ScientificDevelopment, Brazil, and the State of São Paulo Research Foundation, Brazil.From January 2003 to December 2004, he was an Editor with The BrazilianJournal of Power Electronics, edited by Brazilian Power Electronics Society(SOBRAEP). From November 2004 to October 2006, he was the Presidentof SOBRAEP, where he is currently a permanent member of the DeliberativeCouncil. His interests include soft-switching techniques, dc-to-dc convert-ers, switching-mode power supplies, solar/photovoltaic energy applications,electronic fluorescent ballasts, active power-factor correction techniques, andeducational research in power electronics.

Dr. Canesin is an Associate Editor for the IEEE TRANSACTIONS ON POWER

ELECTRONICS.

Luiz Carlos de Freitas received the M.Sc. andPh.D. degrees from the Federal University of SantaCatarina, Florianópolis, Brazil, in 1985 and 1992,respectively.

He is currently a Professor with the Facultyof Electrical Engineering, Federal University ofUberlandia, Uberlandia, Brazil. He has authored avariety of papers particularly in the areas of soft-switching, dc–dc, dc–ac, and ac–dc converters, elec-tronic fluorescent ballasts, and multipulse powerrectifier for clean-power systems. He has published

in PESC’92, APEC’93, PESC’93, and IEEE TRANSACTION ON POWER

ELECTRONICS (Jan. 1995), the evolution of a zero-voltage turn ON and turn OFF

commutation cell that has been largely applied in power electronics research.Dr. de Freitas has been a member of the Power Electronic Research

Group–Grupo de Eletrônica de Potência (NUEP), Federal University ofUberlandia, since 1991.


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