PV Solar Energy Electronics Processing System Operating at the MPP for Commercial Refrigerator Supply Applications

D. C. Martins, D. P. da Silva, A. S. de Andrade, A. J. B. Bottion and K. C. A. de Souza

Federal University of Santa Catarina Department of Electrical Engineering

58109-970 Florianópolis, SC - BRASIL denizar@inep.ufsc.br, doug.p.silva@pop.com.br, andrade@inep.ufsc.br, bottion@inep.ufsc.br, ksouza@inep.ufsc.br

Abstract— The analysis of a PV solar energy electronics processing system, operating at the maximum power point (MPP) for commercial refrigerator supply applications is presented in this paper. The refrigerator is fed from a battery bench using two electronics processing stages. The first one is a step-up push-pull converter that is responsible for the dynamic of the refrigerator and the DC bus voltage control, and the second stage is a full-bridge voltage source inverter with three levels PWM modulation. A closed-loop voltage is used to control the step-up stage, and a closed-loop current to control the compressor starting current. The main features of this system are: simple control strategy, robustness, low harmonic distortion of the load voltage, and natural isolation. The principle of operation, design procedure and experimental results are presented.

I. INTRODUCTION By being a modular and practically non-polluting source

of energy, photovoltaic conversion has received support from many governments throughout the world, being considered a very promising way of generating electric energy. In countries such as Germany, Japan and the United States, the governments have invested significantly in the development of this technology, integrating it into their conventional electric systems, although with a still modest participation of [1], [2] and [3].

In Brazil, the largest percentage of electric energy generation comes from hydroelectric plants, constituting a source of energy that is of low maintenance, low cost and low-pollution, if compared to the equivalent thermoelectric plants. Consequently, the interest in investing in alternative sources of energy is little and there is practically no incentive to do so.

Nevertheless, with the growing globalization of the Brazilian economy and with the sale of many government-owned companies in the electric sector, electric energy has become a source of investment, permitting the focusing on other energy possibilities, principally in the states not blessed with large hydroelectric plants. In addition, needy communities, which are isolated from the electric system, need alternative forms of electric energy generation. In these situations, photovoltaic solar energy can be a very

viable solution, particularly in the north and northeast regions of Brazil where sunshine is abundant. This type of application of photovoltaic solar energy is called a stand-alone system.

The function of a stand-alone system is to feed a specific load in a region where it is not viable to extend the commercial electric network, whether for economic or environmental reasons, or because of Indian reserves, where the passage of distribution lines is not permitted. It is in this context, therefore, that this work is presented, consisting of the study and implementation of an electronic system for processing photovoltaic solar energy for application in residential refrigerators, frequently found in stand-alone systems of the commercial electric network. The principal motivation for the development of this research is directed toward the public health aspect of needy communities that are isolated from the supply centers of the conventional electric network, where the possibility of having an autonomous refrigeration system is fundamental. Small refrigerators can be used for storing vaccines, medicines and materials for clinical examinations. Indigenous communities can also take advantage of this technology. Due to its modular characteristic, a photovoltaic system can be installed in the consuming location, avoiding the use of transmission and distribution networks. In addition, the conversion of solar energy, carried out by the photovoltaic panels, is silent and does not require moving mechanical parts and requires little or no maintenance. The conception of the electronic circuit has as its objective the exploration of the characteristics of the electric motor, proposing a start-up strategy that makes the system technically viable.

The electronic processing system proposed in this article uses a technology that is simple, robust, low cost and easily installed. It consists of three stages. The first stage, made up of a buck circuit, controls the operation of the panels at the MPP (Maximum Power Point) and monitors the charge level of the batteries; the second stage, carried out by a push-pull converter, is responsible for voltage regulation and step-up and for control of the starting current of the compressor, as well as for galvanic isolation; The third stage is a simple full-bridge inverter with three-level sinusoidal

2170-7803-9033-4/05/$20.00 ©2005 IEEE.

PWM. The control strategy of the system employs a closed voltage loop control using a lead-lag compensator and a closed current loop input control that permits the start-up of the refrigerator motor with subnormal voltage.

The topologies that compose the three power stages are simple, well known and dominated by the power electronics community. However, the principal contribution of this work is the connection of these converters, adopting an appropriate control strategy that permits the transfer of energy between photovoltaic solar panels and a commercial refrigerator, making it possible to safely start the compressor and maintain the quality of the energy necessary for the adequate functioning of the motor, without great complexity or cost.

II. EQUIVALENT ELECTRIC MODEL OF THE REFRIGERATOR COMPRESSOR

In feeding refrigerators by photovoltaic panels, the starting current represents one of the most important problems to be solved. Given the profile of the consumer, who generally resides in isolated communities, any proposed method must be simple, cheap, easy to implement and safe. Faced with these requirements, the possibility arose of starting the compressor system with below nominal voltage to reduce the starting current. The compressor system, whose specifications are shown in Table I, is composed of a single-phase induction motor coupled to a gas mechanical compressor driven by a piston. The compressor system starting time versus RMS voltage across its terminals are presented in Fig. 1, which we can verify that 130V is the minimum voltage that permits the effective starting of the compressor system. Fig. 2 shows the simplified equivalent electric model, representative of the compressor system. It consists of two RL series branches, one representing the main winding, which is activated in the starting and in the steady-state condition and the other representing the auxiliary winding, which is only activated during the starting of the motor. To survey the parameters of Fig. 2 it will be used the Table II data, obtained from the compressor system tests with sub nominal voltage and without starting capacitor. So, we have: RC_p_sub = 48.16Ω; LC_p_sub = 51.29Ω; RC_rp_sub = 170.40Ω; LC_rp_sub = 927Ω; and CC_p_sub = 46µF.

Fig. 1: Start time versus RMS voltage

Cc_p_sub

Rc_rp_sub

Lc_p_sub

Lc_rp_sub

Rc_p_sub

Fig. 2: Simplified model of the compressor system III. OPERATION PRINCIPLE For the photovoltaic solar energy application in a

refrigeration system, a convenient electric energy processing is necessary [4]. This is achieved through power static converters, which is possible to arrange the generated electric energy by the photovoltaic panels in quality and voltage level appropriated to supply the compressor syst em. Due to the fact that the system is isolated there is the

necessity to storage the solar energy in excess, and for that we use a bank of batteries. The complete power structure, shown in Fig. 3, is formed by three energy-processing stages. The charge control of the bank of batteries and the MPP solar panels operation are carried out in the first stage, employing a buck converter operating in CCM with 25kHz [1]. The gain of energy obtained by the MPP PV panels operation permits a fast charge of the bank of batteries, minimizing the intermittence of the solar energy.

The second stage, formed by a push-pull DC-DC converter, is responsible for the galvanic isolation, regulation and step-up DC link voltage, and for the control of the compressor starting current. The push-pull converter operates also in CCM with 25kHz. The control of the DC bus voltage and of the starting current are carried out through the implementation of a close loop of voltage and of

TABLE I

COMPRESSOR SYSTEM SPECIFICATIONS

Parameters Data Capacity 30 BTU/h

Start system Relay RMS input voltage 220V

Rated Power 100W Locked-rotor current 6.5 A Operation frequency 50 – 60 Hz

Start capacitor 38 a 46 µF

TABLE II

COMPRESSOR SYSTEM TEST WITH UNDER-VOLTAGE AND WITHOUT START CAPACITOR

Conditions Peak current [A] Voltage phase shift [°]

Starting 4.4 26.0 Steady State 1.9 41.2

218

DC-DCBuck

Converter

PWMCommand

VoltageComparator PWM

Modulator

MPPControl

+- +

-

Inverterin

OpenLoop

Vref1

Bank ofBatteries

+-+

-

F/F Osc

Vref 2

+-

PhotovoltaicPanels

S1

S2

Lf

Cf

Refrigerator

Vp1

Flip / Flop Oscilator

S1

S2

Iin

Iref

Di

Dz

Starting Current Control andDC-DC Voltage Regulation

VoltageComparator

PWMModulator

AndLogic

CurrentComparator

CommandCircuit

Fig. 3: Power structure with its control strategy

current, respectively. The current loop applies a control strategy that reduces the voltage across the terminals of the motor limiting the current during the compressor starting. Therefore, during the motor starting the current loop acts overlapping the voltage loop, keeping the push-pull average input current limited and constant. After the motor starting the input current returns to the nominal values, and the voltage loop passes having priority over the current loop again, regulating the DC bus voltage.

The AC voltage using a three level sinusoidal PWM modulation is carried out in the third stage from a bi-directional current full-bridge inverter. This topology appears as natural propose for the DC-AC conversion with induction motor drive application. The inverter circuit operates in open loop once that the isolation, the voltage regulation, and the starting current control are carried out in the second stage.

A. A Influence of the Full-Bridge Inverter over the DC-DC Push-Pull Converter

The main influence of the inverter circuit over the push-pull DC-DC converter is related with the 120Hz current harmonic component drained by the inverter. To analyze this influence over the capacitor voltage and inductor current, both in the output of the push-pull converter, a simplified linear circuit formed by these parameters is

proposed and presented in Fig. 4. From this figure the following expressions, describing the currents of the circuit, are obtained.

(1) 120120

120

→→

−− = − Cout

Loutout

VI

j Lω

120 120 120

→ →

− −= −Cout out CoutI j C Vω (2)

(3) 120 120 120

→ → →

− −= +Lout CoutI I I

Substituting (1) and (2) in (3) we obtain the analytical expression of the harmonic component of 120Hz drained by the inverter, and presented in (4).

(4) 120120 120 120

120

→→ →

−−= −Cout

out Coutout

VI j j C V

Lω

ω

The 120Hz current harmonic component does not bring

damage to the semiconductors and transformer design. Its influence restrict particularly to the output capacitor design of the push-pull converter [4].

IV. CONTROL STRATEGY In the first processing stage a simple control based on the

219

CoutLout I120HzCout_120ILout_120I

I120

CoutV

+

-

Fig. 4: Influence of the inverter circuit over the push-pull output filter

maximum power ratio technique [1] to keep the photovoltaic panels operate in the MPP is realized. In this technique, the input voltage control is done through a classic compensator with fixed reference voltage, and with the positive feedback conception. So, an increase of the panels output voltage provoke a positive error signal, increasing the converter duty cycle; thus, draining more current and diminishing the voltage across the input capacitor of the buck converter. The inverse happens if there will be a decrease of the panels’ output voltage. To implement this system an only voltage sensor is necessary, according to shown in Fig. 3.

All the control strategy for safety operation and high quality energy, to supply the refrigerator, is established in the second stage by the push-pull converter. It is important to emphasize that the point of view of the load a commercial refrigerator can be considered like a single-phase induction motor coupled to a gas mechanic compressor drive by a piston. To maintain long useful life, little heating and fatigue generated by pulse torques, the induction motor must be feeding with sinusoidal voltage with low harmonic distortion. In the specialized literature many proposes to process photovoltaic solar energy with refrigeration area application are presented. Some of them are very interesting using only one energy processing stage as in [2] and [3]. However, these topologies present a certain control complexity, and due to the fact to use sinusoidal PWM modulation the transformer is designed to the fundamental frequency, that means high volume and weight, being an undesirable system characteristic. Therefore, the proposal of this work is focused in the development of a simple and compact structure with low volume and weight, presenting a control strategy in two processing stages from a bank of batteries. The first stage operating in high frequency to step-up the voltage, provide galvanic isolation, permit the DC bus voltage regulation, and the induction motor safety starting with current limitation. The second stage consists simply of a compact full-bridge voltage inverter operating in open loop.

A. Feedback Control Loop of the Push-Pull DC-DC Converter

For the regulation of the output voltage operating in steady-state, keeping the stability of the system caused by the load disturbance, such as refrigerator gas pressure

variation or even the opening of the refrigerator’s door lighting the internal lamp, and for the input disturbance, that is, increase or decrease of the charge level of the bank of batteries, there is a voltage feedback control loop. The conception of this voltage loop consists in the design of a compensator that guarantee to the feedback system error null to the voltage degree with stable operation. These two requirements can be reaching through a high gain in low frequency and an adequate phase margin.

The convenient choice of a crossover frequency of the plant defines the plant velocity response, while the phase margin established the dynamic of this response. The design methodology of the voltage compensator is very simple; it is based in [4]. It uses two compensators, one in phase-lead that determines the system dynamic, and other in phase-lag that guarantee null static error. The synthesis of a unique PID compensator that combines these two characteristics from the cascade of the two compensators is contemplated in this proposal. The transfer function arranged in a linear way around the push-pull operation point considering the LC filter and the load is represented in (5) as in [5]. From this it is possible to obtain the resonance frequency and the crossover frequency of the plant. These information are important to determine the phase lead compensator. For the modeling of the plant, and consequent compensator design application, we define Rout as the relation between the square of the steady state output voltage (Vout2) and the starting output power (Pout-P), both for the push-pull converter. The power structure with its control strategy is represented in Fig. 3.

(5)

( )( )

( )

^

^

sec _

2

1

1 1

= =

⋅ +⋅

⎛ ⎞ ⎛ ⎞+ + + +⎜ ⎟ ⎜ ⎟

⎝ ⎠ ⎝ ⎠

out Svd S

S

in nom SE f

fpri SEf f SE f

out out

vFT

dN V s R C

LN Rs L C s R CR R

Where: RSE represent the equivalent series resistance of

the filtering capacitor Cf. The control loop of the input current has as function to

limit the power drained by the refrigerator during the starting condition in a way to feasibility the compressor starting strategy with sub nominal voltage. This feedback control loop acts only when the input current reaches a detrimental value to the system. If so, is the current compensator that defines the duty cycle of the converter. This current value is defined in the project of the system and depends on the refrigerator specifications. Once finished the starting condition and the input current return to operation safety level, is the voltage loop that control the whole system. The transfer function related to this control loop is represented in (6). It presents only one pole in the origin, having an integrator behavior.

220

(6) ( )

( )

( )

^sec _

^

⋅= =

⋅in S out p

id Spri fS

N ViFT

N s Ld

From Fig. 3 we verify that the control circuit uses two

sensors, one for the voltage loop and other for the starting current loop, both applied in the DC-DC push-pull converter. The voltage loop sensor, formed by a resistive divisor, maintains the push-pull output DC voltage regulated in 400V. In the voltage loop there is a voltage compensator, which the output signal is send to a PWM comparator circuit for generating the switches drive signals. The second circuit, with Hall effect, monitors the batteries current; it has a large band frequency response, reproducing with accuracy the instantaneous current. A passive first order low-pass filter filters this current, to control the batteries average current. The filter output signal is injected in a current compensator and then follows to the terminal 9 of the SG3525A integrator, to control the compressor starting current. The current compensator is implemented through the operational LM318. In the output of this operational we have two diodes (DZ and Di). The Zener diode DZ has two functions, to avoid the saturation of the operational circuit and the negative voltage in the terminal 9 of the SG3525A when Di conducts. The diode Di is responsible by the actuation of the current control loop, that is, while the battery current is smaller than the reference current the voltage loop control the system; from the moment that the battery current is equal or superior to the reference current the output voltage of the current compensator began to decrease until to be smaller than the output voltage of voltage compensator. In this moment the current loop impose the duty cycle of the converter, controlling the refrigerator current.

V. DESIGN PROCEDURE AND EXAMPLE Specifications: Pout-Start = 350W -Starting output power; Pout-SS = 150W -Steady-State output power; Vout-SS = 400V -Steady-State DC bus voltage; Vout-Start = 250V -Starting DC bus voltage; fS = 25kHz -Switching frequency; Vin-nom = 24V -Batteries nominal input voltage; Vin-min = 21V -Batteries minimum input voltage; Vin-max = 28.8V -Batteries maximum input voltage; Dmax = 0.8 -Maximum duty cycle; Dmax-Start = 0.5 -Maximum duty cycle in the starting

condition; η = 90% -Estimated efficiency; ∆Vpp = 10V -Peak-to-peak DC bus voltage ripple; ∆I = 10% -Current ripple in the DC bus

inductor filter. The maximum current through the switches in the

moment of the compressor starting is formulated by (7). The same current flows through the transformer primary windings and through the bank of batteries.

(7) Primin max

350 37.04A0.9 21 0.5

−− − − −

− −= = = =

⋅ ⋅out Start

S peak Start peak Startin Start

PI IV Dη

The maximum current through the transformer secondary

winding is given by (8).

(8) max

350 2.8A250 0.5

−− −

− −= = =

⋅out Start

Sec peak Startout P Start

PI

V D

From the output voltage and de maximum duty cycle, both in the starting condition, it is possible to determine the push-pull transformer turns ratio. Thus:

(9) Pri max min

2501.1 1.1 26.190.5 21

−

− −= = = =

⋅ ⋅Sec out Start

Start in

N VaN D V

⇒ a = 26 For the steady-state condition we have:

(10)Pri

min max

150 9.92A0.9 21 0.8

−− − − −

−= = = =

⋅ ⋅out SS

S peak SS peak SSin

PI I

V Dη

(11)max

150 0.47A400 0.8

−− −

−= = =

⋅out SS

Sec peak SSout SS

PI

V D

The filtering inductance design depends on the current

ripple. Therefore:

(12) max3

28.826 104mH8 8 25 10 0.036

−= = ⋅ =⋅ ⋅∆ ⋅ ⋅ ⋅f

inf

S L

VL a

f I

For calculation of the filtering capacitance we must consider the full-bridge inverter influence over the push-pull converter [4]. This influence is related to the current harmonic component of 120Hz drained by the inverter circuit. From (4) we obtain (7) that give us the push-pull filtering capacitance value in function of the parameters of this converter.

(13) 1202

120 120

1= − +

∆fCout out

IC

V Lω ω

For a power of 150VA drained by the converter in steady

state and admitting that the peak rectifier current be equal to the fundamental component, thus the value of I120 is approximately 1A peak. ∆VCout represents ripple peak value that according to the specifications is 5V. So:

(14) ( )2

1 1 282.17µF 3302 120 5 2 120 0.104

= + = ⇒ =⋅ ⋅ ⋅ ⋅

f fC C Fµπ π

The inverter circuit operates in open loop and has only

one function to carry out the inversion of the push-pull output DC voltage, using a three level PWM sinusoidal modulation. Therefore, its design follows the traditional

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procedures. The output sinusoidal voltage with low harmonic distortion is obtained from low pass LC filter, which the values are given below.

(15) 1.6 ; 4− −= =f FB f FBL mH C Fµ

Although the compressor starting represents the critical moment of the system it occurs in a very short interval of time with sub nominal voltage and with controlled and limited current using a current close loop. Therefore, in the design of this item it will be observed only the steady-state situation, which represents the large part of the operation system.

The average power and current delivered by the batteries in steady-state condition will be:

(16) 150 167W and0.9

−= = =out SSBav

PP

η

(17) 167 7A24

= = =BavBav

Bcc

PI

V.

Ch1:Output voltage

Ch2:Output current

Ch1: 100 V/div Ch2: 500 mA/divTime: 4 ms/div

Fig. 5: Voltage and Current in the compressor system

Harmonic spectrum as a percentage of he fundamental amplitude

2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 400.0%

0.2%

0.3%

0.5%

0.6%

0.8%

0.9%

1.1%

1.2%

1.4%

1.5%THD = 1,78%

Fig. 6: Output voltage harmonic spectrum of the inverter

As it is a refrigeration system where the operation must be uninterrupted we want that the bank of batteries deliveries a current of 7A for at least 16 hours without happening the total batteries discharge. Thus, the necessary numbers of batteries will be:

(18)16 7 1.8 260

⋅ ⋅= = = ⇒ =avA B

B BC

B IN N

B

Where: NB → Minimum number of batteries; BA → Battery autonomy: 16 hours; BC → Battery capacity: 60Ah. Two lead-acid batteries connected in series (12V/100Ah)

were chosen. The photovoltaic panels used in the design can deliver

3Ah (Amps-hours) with a solar radiation of 1000W/m2. In the worst case the average solar radiation, in our region (Florianopolis/Santa Catarina – Brazil), is about 2500W/m2 per day. Thus:

(19) 3 2500 7.5Ah1000

⋅ ⋅= = =Rs av

dI R

AhRs

Where: Ahd →Amperes-hours that each photovoltaic panels

delivery per day; Rav → Average solar radiation: 2500W/m2/day (worst

situation); Rs → Standard solar radiation: 1000W/m2; IRs → Amperes-hours delivered by the photovoltaic

panels for the radiation Rs; 3Ah. Thus, the number of photovoltaic panels is given by:

(20) 7 0.93photovoltaic panels7.5

= = =Ld

AhNp

Ah

Where: AhL → Ampere-hours delivery to the load per

day. We opted to connect two photovoltaic panels of 12V in

series.

VI. EXPERIMENTAL RESULTS A laboratory prototype rated 150W was built to evaluate

the proposed system. It feed a commercial refrigerator with 220V/60Hz. The main specifications of the whole system are given in the previous item. Fig. 5 shows the steady-state compressor current and voltage waveforms. The voltage harmonic spectrum is shown in Fig. 6, where it is indicated the value 1.78%. The quality of the output voltage waveform is very important for the useful life of the induction motor. In Fig. 7 are presented the waveforms of the output voltage versus push-pull output inductor current, and versus the batteries current, with the objective to confirm the action of the control strategy, emphasizing the good behavior of the proposed system. From Fig. 7 we can

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observe that from the limitation of the input average current we can limit the output voltage. During all the time that the current is maintained limited the push-pull output DC voltage is kept constant in approximately 250V. The starting current in the refrigerator motor is shown in Fig. 8. The efficiency curve of the whole system is presented in Fig. 9.

0,89

0,90

0,91

89 105 113 130 143 155 171 189 201

Input power [W]

Fig. 9: Efficiency curve of the whole system

Ch1: Push-Pull output voltage

Ch2: Push-Pull output inductor current

(a)

Ch1: Push-Pull output voltage

Ch2: Battery current

VII. CONCLUSION This paper has presented the analysis of static conversion

electronics system for photovoltaic solar energy processing with applications in the refrigeration area. The system is particularly simple and robust, using low cost technology. The power electronics structure is divided in three stages. The first one carries out the batteries charge control and forces the panels to operate in the MPP. The second stage operates with two feedback control loops; the first loop

permits to regulate the DC bus voltage, and the second one limits the motor starting current; in this stage it is also carried out the galvanic isolation between the solar panels and the load. The third stage operates in open loop; in this stage we have the inversion of the DC bus voltage using a three level PWM sinusoidal modulation.

The adopted control strategy permits to generate a sinusoidal output voltage with low harmonic distortion, reducing the parasitic torques, the losses and the motor vibration, increasing the motor useful life. The high frequency operation permits the reduction of the magnetic components volume and the capacitors.

The proposed system can be applied in residential or/and commercial buildings, for low or high power. It can operate with commercial available refrigerator and photovoltaic modules, avoiding any kind of adaptation for connecting them.

REFERENCES [1] D. C. Martins, C. L. Weber, A. S. de Andrade & O. H. Gonçalves :

“Photovoltaic Solar Energy Processing Using a Simple Technique to Operate in the Maximum Power Point”, in Proc. PVSEC-14 – International Photovoltaic Science and Engineering Conference, Bangkok, Thailand, 2004, vol. 2, pp. 869-870.

Ch2: 1 A/divBase de tempo: 400 ms/div

Fig. 8: Refrigerator motor current during the starting transient

Progressive start Current loop Voltage loop

Ch1: 100 V/div Ch2: 500 mA/divTime: 250 ms/div (b)

Progressive start Current loop Voltage loop

Ch1: 100 V/div Ch2: 500 mA/div [2] H. Poor, An Introduction to Signal Detection and Estimation. New York: Springer-Verlag, 1985, ch. 4. Time: 250 ms/div

Fig. 7: (a) Output voltage versus filtering inductor current of the push-pull converter, (b) Push-pull output voltage versus batteries current [3] K. H. Edelmoser & F. A. Himmelstoss, “New High Efficiency Current

Fed DC-to-AC Inverter”, in Proc. 2nd World Conference and Exhibition on Photovoltaic Solar Energy Conversion, Viena, Austria, 1998.

[4] U. Herrmann & H. G. Langer, “Low Cost DC to AC Converter for Photovoltaic Power Conversion in Residential Applications”, in Proc. 24th Power Electronics Specialists Conference, Seattle, Washington, USA, 1993, pp. 588-594.

[5] D. P. da Silva, “Electronic System for Photovoltaic Solar Energy Processing Operating in the Maximum Power Point”, Master dissertation, Institute of Power Electronics, Dept. Elect. Eng., Federal Univ. of Santa Catarina, Florianópolis, SC – Brazil, 2003.

[6] M. L. Heldwein, “Three-Phase Rectifier Unit of High Power and Performance for Telecommunication Application”, Master dissertation, Institute of Power Electronics, Dept. Elect. Eng., Federal Univ. of Santa Catarina, Florianópolis, SC – Brazil, 1999.

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