Single-phase PWM AC/AC Semiconductor Transformer Topologies and Applications

H , (0) = D/(1- D)

Zbigniew Fedyczak, Ryszard Strzelecki, Grzegorz Benysek University of Zielona Gora, Institute of Electrical Engineering

U1. Podgoma 50,65-246 Zielona Gora, Poland

H , (0) = D/(1- 0)

Abstract- This paper deals with the AC voltage transformation circuits, which contain matrix or matrix- reactance P W M AC line conditioners. These circuits can be treated as P W M AC/AC semiconductor transformers. In this paper the review of single-phase topologies are presented. The review covers both non-isolated and isolated one as well as single or two-quadrant structure. Furthermore there are shown the averaged models, their four terminal chain parameters and outlined some exemplary applications of presented AC voltage transformation circuits as well.

I. INTRODUCTION

In industrial practice the AC line conditioners with thyristor power controllers are commonly used as the AC voltage transformation circuits. Major disadvantages of those are: generation of higher harmonics in the source current, generation of displacement power at phase angle control and generation of subharmonics at integral control. In order to eliminate these unfavourable properties a matrix PWM AC line conditioners are suggested [l-131. For these conditioners, the increase of the load voltage above the supplying voltage is not possible without additional electromagnetic transformer. In [ 14-20] there are presented, the basic energetic properties of matrix-reactance PWM AC line conditioners, which have the capability to increase the

Buck I Boost

S I -

Zeta I Sepic

AC load voltage above the AC line supplying voltage without an electromagnetic transformer. These conditioners contain additional passive elements and their topologies are similar to well-known D O C converter topologies. Both matrix and matrix-reactance PWM AC line conditioners can be treated as PWM ACIAC semiconductor transformers. In works [21-251 description and confirmation of interesting application abilities to direct buck or buck-boost AC voltage transformation either in single or three-phase circuits are presented.

The main aim of this paper is review of single-phase topologies of AC voltage transformation circuits covers both non-isolated and isolated one as well single or two- quadrant structure. There are the averaged models of presented circuits and their four terminal chain parameters as well [26-291. Furthermore some exemplary applications are also presented.

11. SINGLE-PHASE TOPOLOGIES

A. Non-isolated circuits

The basic and symmetrical single-phase ACIAC semiconductor transformer topologies are shown in fig. 1.

H , (0) = - D/(1- D)

I /

Cuk - Modification 1

H , (0) = (1 - 20)/(1- D )

r--

Cuk

H , (D) = - D/(1- D)

Cuk - Modification 2

!EITIb H , (0) = (1 - D)/(l- 2 0 )

Fig. 1. The basic and symmetrical topologies of single-phase AC/AC semiconductor transformers, Hu - voltage transfer function

0-7803-7262-X/02/$10.00 0 2002 IEEE. 1048

Among of topologies shown in fig. 1 only the buck one has a v t r i x structure. Remaining structures (boost, buck- boost, Cuk, Zeta and Sepic) belong to matrix-reactance family and enable increasing load voltage valu: above supplying voltage value with (buck-boost and Cuk) or without (boost, Zeta and Sepic) phase inverting [l-3, 5, 1 1 , Simplified structure of single-phase isolated AC/AC 13, 14, 16, 18-20]. semiconductor transformer topologies are shown in fig. 3.

In fig. 2 symmetrical topologies of two quadrant single- In these circuit additional voltage transformation is realized phase AC/AC semiconductor transformers are shown. In by means of isolating transformer, as it is shown in fig. 4

by connection of single quadrant topologies, which are shown in fig. 1.

B. ISOLATED CIRCUITS

the Fig. 2 shown that these structures Buck

H , = D, -D, H , (0) = 2 0 - 1

Cuk

.e simply obtained Boost

r

Zeta

H , =(Dl -D,)/(l-D,)(l-D,) H , (0) = (20 - l)/D(l- D )

Sepic

Fig. 2. Two-quadrant topologies of single-phase AC/AC semiconductor transformers, H" - voltage transfer function (H@) for case when D = DI = 1 - 4)

I Buck I Boost I Push-pull

Zeta I Sepic I Cuk I

Buck-Boost I Zeta I Sepic 11 I

Fig. 3. Simplified structure of single-phase isolated AC/AC semiconductor transformers

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a ) U L [ k V l 4

0

- 4 6 0 4 0 ~ i m e [m S I

0

- 44 0 Tim e [ m s ] 6 0

Fig. 4. Load voltage time waveforms of single-phase isolated AC/AC semiconductor transformer with Cuk topology,

a) for transformation ratio 1 :1, b) for transformation ratio 2: 1

111. AVERAGED MODELS

On the base of averaged state-space method introduced by Middlebrock and Cuk [26] for DC/DC converters and extended by [27, 291 for ACIAC ones, for sufficiently small switching period Ts, x(t ) = X(t) , y(t) = j ( t ) where E(t)andy(t) given as a solution the basic averaged state- space description (over a single switch period Ts):

(1) x = A(D)F + B(D)ii

= C(D)F

where: D - duty factor of switch control signal, A(D) = A I D

From (1) one can easily obtain the substitute circuit realizations shown in fig. 5 for buck family of non-isolated AC/AC semiconductor transformers with unipolar voltage transfer function and in fig.6 for boost one [28].

+ Az( 1-D), B(D) = BID + Bz( 1-D), C(D) = CID + Cz( 1-D).

Fig. 5 . Circuit realizations of steady-state averaged models for buck family of ACIAC semiconductor transformers, a) buck, b) buck-boost,

c) zeta topology A=, AL, A - four-terminal chain parameters of basic structure, load circuit

and complete circuit collected in tabl. AI

Fig.6. Circuit realizations of steady-state averaged models for boost family of AC/AC semiconductor transformers,

a) boost topology, b) Cuk topology, c) Sepic topology AS, Ac, AL, A - four-terminal chain parameters of source circuit, basic

structure, load and complete circuit collected in tabl. A2

Exemplary calculation and simulation test results of voltage transfer function for buck and boost families of presented transformers are shown in fig. 7 [28].

a) H U L [VWI 4 I l l I / / - - Calculation

o -Simulation 2

1

1

'0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1

1

0 0 0 1 0 2 0 3 0 4 0 5 06 0 7 0 8 0 9 1

-LO 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 D

Fig. 7. Magnitude and phase of voltage transfer function for, a) buck family, b) boost family of presented circuit

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w. OUTLINE OF EXEMPLARY APPLICATIONS

- - - There are some interesting exemplary applications of presented transformers in this section. An example of direct ACIAC semiconductor transformer utilisation is shown in fig. 8. In similar applications another topology (Cuk, Zeta or Sepic) shown in fig. 1 can be used.

- - ~

Fig. 8. Sodium lamp supplier with buck-boost AC/AC semiconductor transformer

There is successive example in fig. 9, which depicts serial voltage regulator with two-quadrant buck ACIAC semiconductor transformer shown in fig. 2. Detailed description of this regulator with two auxiliary resonance switches is presented in [22], whereas in fig.10 there are exemplary time waveforms, which illustrate one operation.

UL

Fig. 9. Serial voltage regulator with two-quadrant buck AC/AC semiconductor transformer

Next example deals with dirett ACDC converter without input rectifier, which employs Cuk modified circuit. In this circuit, shown in fig. 11, an option with bipolar voltage transfer function and unipolar switches are used. Detailed description of this ACDC converter is presented in [21], whereas exemplary open loop time waveforms depicted one operation are shown in fig. 12.

500

0

-500

40 Time [ms] 60

Fig. 10. Time waveforms of load voltage UL in serial voltage regulator shown in fig. 9

In fig. 13 an example of single-phase SVC with ACIAC semiconductor transformer as a controlled reactance is shown [23, 251. Experimental time waveforms obtained in this transformer,are shown in fig. 14.

lJ [kVI 2

1

0

-1 40 T i m e [ms] 60

Fig. 12. Time waveforms of load voltage UL in open loop direct ACDC converter shown in fig. 11

Fig. 13. SVC with AC/AC semiconductor transformer as a controlled reactance, a) schematic diagram, b) phasor diagram for inductive load

5 " 5 I <on m i l I Fig. 14. Voltage and current time waveforms in SVC shown in fig.13a

for D = 0.8

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The final example with boost ACIAC semiconductor transformer to compensate of voltage sags in electric power distribution systems is shown in fig. 15 [24].

Parameter

'?=Cl

u2 =a A C 1 2 = (9)

it =o

A C 2 2 =[?) E, =a

- Fig. 15. Single-phase sag compensator with boost transformer

Formula for topology: Boost CUk Sepic

1-D (1-D)2 -w2L,C ~ ( i - D)

1-D ~ ( i - D)

(1 - D ) [ ~ ~ c ( L , + L, - 11 ~ L , C - D

jclac, jw[o-D)zL, -Ls(w2L,C-D2)]

j & - j(1- D)WC 0 ~ ( i - D) w2LLC - D

- 1 m 2 ~ , ~ - ~ 2 wZL,C-D2 1-D ~ ( i - D) ( ~ - D ) ( ~ z L , c - D )

V. CONCLUSIONS

In this paper the review of topologies and outline of exemplary applications of single-phase ACIAC semiconductor transformers have been presented. The averaged method used to modelling of presented transformers is very useful to one energetic properties investigation. The four terminal descriptions by chain parameters employing is natural and useful approach to study next effective applications of presented transformers.

Presented application examples confirm interesting possibilities of AC/AC semiconductor transformers. As so far mainly single quadrant of one transformers find usefully applications. In authors opinion next proposition of presented ACIAC semiconductor transformer applications will emerge in the near feature.

APPENDIX TABLE A1

FOUR TERMINAL Ac AND A CHAIN PARAMETERS FOR AVERAGED MODELS OF BUCK FAMILY CONDlTIONERS

TABLE ~2 FOUR TERMINAL Ac AND A CHAIN PARAMETERS FOR AVERAGED MODELS OF BOOST FAMILY CONDlTIONERS

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TABLE ~2 CNTD.

U2LsC, A m -- Acll + j A c I 2 K ~

All =(3 IL =o I - D

A12 = [2) 1-D A,,,

A , =(?) 1 - D A,,

&

iwc, g‘=O

A21 =[&) 1 - D ACZ1 + j A c d G LL =o

1 -

EL =o

Acll + j A c 1 2 K ~

A C I 2

A,,, + j A c 2 , 4

A,,

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