ac to ac 3-phase matrix converter

8/10/2019 AC to AC 3-Phase Matrix Converter

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CERTIFICATE

This is to certify that the progress report entitled, Modeling,Simulation

and Analysis of Matrix Converters Using Venturini Algorithm

submitted byGajendra JephandNeha Bagariin partial fulfillment of the

requirements of the award of the degree of Bachelor of Technology in

Electrical Engineeringat the Indian Institute of Technology (Banaras

Hindu University),Varanasi, is an authentic work carried out by themunder my supervision and guidance. To the best of my knowledge the matter

embodied in the project report has not been submitted to any other

University/Institute for the award of degree or diploma.

Supervisor Approved for Submission

(Dr. S. K. Singh) (Dr. S. P. Singh)

Assistant Professor Professor and HeadDepartment of Electrical Engineering Department of Electrical Engineering

Indian Institute of Technology(BHU) Indian Institute of Technology(BHU)Varanasi-221005 Varanasi-221005


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ACKNOWLEDGEMENT

We take this opportunity to express our deep sense of gratitude andindebtedness to our esteemed supervisorDr. S. K. Singh, Assistant Professor,

Department of Electrical Engineering, Indian Institute of Technology(BHU),Varanasi,(Uttar Pradesh),India, who has helped us enormously and always

inspired us by his indispensable guidance and encouragement during the

whole long project work. He has always supported and strengthened us inmany aspects. We consider ourselves fortunate to have worked under his

supervision in the field of Modeling, Simulation and Analysis of MatrixConverter Using Venturini Algorithm.

We are highly grateful to Dr. S. P. Singh,Professor and Head,Department of Electrical Engineering, Indian Institute of Technology,

Banaras Hindu University, for providing necessary facilities andencouragement during the course of the work.

We would also like to thank our seniors and classmates for their valuable

suggestions that proved helpful.

We would also like to express our feeling toward our parents and god

who directly or indirectly encouraged and motivated us during this work .

Last but not the least we would like to thank all those who have done

valuable work in matrix converter paving the way for us.

Gajendra Jeph Neha Bagari


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Index

S.No. Content Page No.

1. Abstract ..........................................................5

2. Introduction...................................................6

3. Basic Topology..............................................7-8

4. Performance................................................9-11

5. Implementation

of Matrix converter....................................11-19

6. Modulation Technique

(Venturini Method)....................................20-24

7. Practical Issues......................................... 25-28

8. Simulation and Result..............................29-39

9. Conclusion.................................................40-41

10. Future Work................................................42

11. References....................................................43


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Abstract

The matrix converter is an array of controlled semiconductor switches that connects

directly the three-phase source to the three-phase load.This converter has several

attractive features that have been investigated in the last two decades. In the last fewyears, an increase in research work has been observed,bringing this topology closer to the

industrial application.A matrix converter (MC) which makes directly AC-AC power

conversion is modeled using Matlab & Simulink and its working principles are analyzed.The gate signals of the power switches of MC are produced using Optimum

Amplitude-Venturini Modulation (OAVM) method.

This method provides the amplitude of output voltage up to 86.6% of input voltage, andunity fundamental displacement factor at the input regardless of the load displacement

factor.


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Introduction

The matrix converter providing directly ac-ac power conversion is one of the mostinteresting members of the power converter family. Matrix converter firstly introduced in1976 started to improving after papers of Venturini and Alesina in 1980. The proposed

method by these authors is known as the Venturini method or the direct transfer functionapproach. In this method, gate-drive signals for the nine bidirectional switches are

calculated to generate variable-frequency and/or variable-amplitude sinusoidal output

voltages from the fixed-frequency and the fixed-amplitude input voltages.The MC has some advantages as follows according to traditional converter -

Generation of output voltages with the desirable amplitude and frequency;

Energy regeneration aptitude to the mains; Sinusoidal input and output currents;

Controllable of input displacement factor regardless of the load; Compact design due to the lack of dc-link components for energy storage.

But the matrix converter has also some disadvantages. First of all it has a maximum

input output voltage transfer ratio limited to 87 % for sinusoidal input and output

waveforms. It requires more semiconductor devices than a conventional AC-AC indirectpower frequency converter, since no monolithic bi-directional switches exist and

consequently discrete unidirectional devices, variously arranged, have to be used for each

bi-directional switch. Finally, it is particularly sensitive to the disturbances of the inputvoltage

system.

The physical realization of the MC is very difficult, and the number of the devices in

the power circuit is higher than that of the inverter. Therefore, it is crucial to obtain aneffective model and to test it before constructing a working prototype of the MC.However, popular circuit-oriented simulation software packages such as PSPICE, PSIM

and Matlab&Simulink have not got the model of an MC as a standard block in their

libraries.


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1. BASIC TOPOLOGY

The matrix converter consists of 9 bi-directional switches that allow any output phase to

be connected to any input phase. The circuit scheme is shown in Fig.1. The inputterminals of the converter are connected to a three phase voltage-fed system, usually the

grid, while the output terminal are connected to a three phase current- fed system, like aninduction motor might be. The capacitive filter on the voltage- fed side and the inductive

filter on the current- fed side represented in the scheme of Fig.1 are intrinsically

necessary. Their size is inversely proportional to the matrix converter switchingfrequency.

Fig -Circuit scheme of a three phase to three phase matrix converter

tWith nine bi-directional switches the matrix converter can theoretically assume 512 (29)different switching states combinations. But not all of them can be usefully employed.

Regardless to the control method used, the choice of the matrix converter switching states

combinations (from now on simply matrix converter configurations) to be used mustcomply with two basic rules. Taking into account that the converter is supplied by a

voltage source and usually feeds an inductive load, the input phases should never be

short-circuited and the output currents should not be interrupted. From a practical point ofview these rules imply that one and only one bi-directional switch per output phase must

be switched on at any instant. By this constraint, in a three phase to three phase matrixconverter 27 are the permitted switching combinations.

A direct MC (DMC) is a single-stage converter with mn bidirectional power switchesthat connects an m-phase voltage source to an n-phase load . The DMC of 33 switches,is

the most important from a practical point of view because it connects a three-phase

source to a three-phase load, typically a motor.


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Sij(t)=1,switch on

0,switch off

The power filter at the input of the converter mitigates the high-frequency components of

the MC input currents, generating almost sinusoidal source currents and avoiding thegeneration of overvoltages. Overvoltages are caused by the fast commutation of input

currents due to the presence of the short-circuit reactance of any real power supply. The

inductance of the input filter Lf and capacitor Cf provide series resonance for anyharmonic coming from the three-phase mains and parallel resonance for current

harmonics generated in currents iA,iB, and iCthrough the operation of the switches. When

the frequency of these harmonics is close to the resonance frequency of the filter, strongoscillations will appear. The design of the input filter is an important issue in the

operation of the DMC. Due to the presence of capacitors at the input of the DMC, only

one switch on each column can be closed. Furthermore,the inductive nature of the loadmakes it impossible to interrupt the load current suddenly, and therefore, at least one

switch of each column must be closed.

In order to develop a modulation strategy for the MC, it is necessary to develop a

mathematical model, which can be derived directly

vo= T(Sij)vi

ii=T(Sij)Tio

Where

vo=[va vb vc]T is the output voltage vector,

vi=[vA vBvC]T is the input voltage vector,

ii=[iAiB iC]T is the input current vector,

io=[iaibic]T is the output current vector, and

T(Sij) is the instantaneous transfer matrix of the DMC as a function of the switches Sij,

which is defined as


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2.Performance

This section gives a short description of what are the performance of a matrix converter.A qualitative analysis of some performance parameters is carried out. Some numerical

results based on simplified model of a matrix converter system are also shown.

2.1 The output voltage

Since no energy storage components are present between the input and output side of thematrix converter, the output voltages have to be generated directly from the input

voltages. Each output voltage waveform is synthesized by sequential piecewise sampling

of the input voltage waveforms. The sampling rate has to be set much higher than bothinput and output frequencies, and the duration of each sample is controlled in such a way

that the average value of the output waveform within each sample period tracks thedesired output waveform . As consequence of the input-output direct connection, at anyinstant, the output voltages have to fit within the enveloping curve of the input voltage

system. Under this constraint, the maximum output voltage the matrix converter cangenerate without entering the over- modulation range is equal to 3/2 of the maximuminput voltage: this is an intrinsic limit of matrix converter and it holds for any control law.

Entering in the over- modulation range, thus accepting a certain amount of distortion inthe output voltages and input currents, it is possible to reach higher voltage transfer ratio .

In Fig.2 the output voltage waveform of a matrix converter is shown and compared to the

output waveform of a traditional voltage source inverter (VSI). The output voltage of aVSI can assume only two discrete fixed potential values, those of the positive and

negative DC-bus. In the case of the matrix converter the output voltages can assumeeither input voltage a, b or c and their value is not time-invariant: the effect is a reductionof the switching harmonics.

Fig.2 Output voltage waveforms generated by a VSI and a matrix converter.

(a) VSI (b) Matrix converter


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2.2 The input current

Likewise to the output voltages, the input currents are directly generated by the output

currents, synthesized by sequential piecewise sampling of the output current waveforms.If the switching frequency of the matrix converter is set to a value that is much higherthan the input and output frequency, the input currents drawn by the converter are

sinusoidal: their harmonic spectrum consists only of the fundamental desired component

plus a harmonic content around the switching frequency. In Fig.3 the input current drawnby a matrix converter for a 2 kHz switching frequency is shown. It can be noted that the

amplitude of the switching harmonic components is comparable to the fundamental

amplitude. It is then obvious that an input filter is needed in order to reduce the harmonicdistortion of the input line current to an acceptable level. It follows that care should be

used in speaking about matrix converters as an all silicon solution for direct AC/AC

power conversion, since some reactive components are needed. The matrix converter

performance in terms of input currents represent a significant improvement with respectto the input currents drawn by a traditional VSI converters with a diode bridge rectifier,whose harmonic spectrum shows a high content of low-order harmonics. By the light of

the standards related to power quality and harmonic distortion of the power supply this is

a very attractive feature of matrix converter.

2.3 The input power factor control

The input power factor control capability is another attractive feature of matrix converters,

which holds for most of the control algorithms Despite of this common capability it isworth noting that a basic difference exists with respect to the load displacement angle

Fig. 3- Matrix converter input current and harmonic spectrum (switching

frequency 2kHz) [4]


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implementation, which has represented a main obstacle to the industrial success of thematrix converter, is the commutation problem. The commutation issue basically risesfrom the absence, in the matrix converters, of static freewheeling paths. As consequence

it becomes a difficult task to safely commutate the 20 current from one bi-directional

switch to another, since a particular care is required in the timing and synchronisation of

the switches command signals.

a) Diode bridge with a single IGBT

b) Two anti-paralleled IGBTc) Two anti-paralleled NPT-IGBT

a).Diode bridge with a single IGBT

b).Two anti-paralleled IGBT with series diodes

c).Two anti-paralleled NPT-IGBTs with reverse blocking capability

Fig.5 Possible discrete implementations of a bi-directional switch[4]


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3.1.1 Realization With Discrete Semiconductors

The diode bridge bidirectional switch cell arrangement consists of an insulated gatebipolar transistor (IGBT) at the center of a single-phase diode bridge arrangement as

shown in Fig. 5(a). The main advantage is that both current directions are carried by thesame switching device, therefore, only one gate driver is required per switch cell. Device

losses are relatively high since there are three devices in each conduction path. The

direction of current through the switch cell cannot be controlled. This is a disadvantage,as many of the advanced commutation methods described later require this. The common

emitter bidirectional switch cell arrangement consists of two diodes and two IGBTs

connected in antiparallel as shown in Fig. 5(a). The diodes are included to provide the

reverse blocking capability. There are several advantages in using this arrangement whencompared to the previous example. The first is that it is possible to independently control

the direction of the current. Conduction losses are also reduced since only two devicescarry the current at any one time. One possible disadvantage is that each bidirectional

switch cell requires an isolated power supply for the gate drives. The common collector

bidirectional switch cell arrangement is shown in Fig. 5(b). The conduction losses are thesame as for the common emitter configuration. An often-quoted advantage of this method

is that only six isolated power supplies are needed to supply the gate drive signals .However, in practice, other constraints such as the need to minimize stray inductance

mean that operation with only six isolated supplies is generally not viable. Therefore, the

common emitter configuration is generally preferred for creating the matrix converter

bidirectional switch cells. Both the common collector and common emitter configurationscan be used without the central common connection, but this connection does provide

some transient benefits during switching. In the common emitter configuration, thecentral connection also allows both devices to be controlled from one isolated gate drive

power supply.

3.1.2 Integrated Power Modules

It is possible to construct the common emitter bidirectional switch cell from discretecomponents, but it is also possible to build a complete matrix converter in the package

style used for standard six-pack IGBT modules. This technology can be used to develop a

full matrix converter power circuit in a single package, as shown in Fig. 6.This has been done by Eupec using devices connected in the common collector

configuration (Fig.7) and is now available commercially . This type of packaging willhave important benefits in terms of circuit layout as the stray inductance in the current

commutation paths can be minimized.

If the switching devices used for the bidirectional switch have a reverse voltage blocking


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capability, for example, MOS turn-off thyristor (MTOs), then it is possible to build thebidirectional switches by simply placing two devices in antiparallel.

Fig. 6 - Power stage of a matrix converter[1]

Fig. 7. The Eupec ECONOMAC matrix module[1]

3.2 CURRENT COMMUTATION

Reliable current commutation between switches in matrix converters is more difficult toachieve than in conventional VSIs since there are no natural freewheeling paths. The

commutation has to be actively controlled at all times with respect to two basic rules.

These rules can be visualized by considering just two switch cells on one output phase ofa matrix converter. It is important that no two bidirectional switches are switched on at

any instant, as shown pictorially in Fig. 8(a). This would result in line-to-line shortcircuits and the destruction of the converter due to over currents. Also, the bidirectionalswitches for each output phase should not all be turned off at any instant, as shown in Fig.

8(b). This would result in the absence of a path for the inductive load current, causinglarge overvoltages.


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(a) (b)

Fig 8- (a) Avoid short circuits on the matrix converter input lines. (b) Avoid open

circuits on the matrix converter output lines.[1]

These two considerations cause a conflict since semiconductor devices cannot be

switched instantaneously due to propagation delays and finite switching times.

3.2.1 Basic Current Commutation

The two simplest forms of commutation strategy intentionally break the rules given above

and need extra circuitry to avoid destruction of the converter. In overlap currentcommutation, the incoming cell is fired before the outgoing cell is switched off. This

would normally cause a line-to-line short circuit but extra line inductance slows the rise

in current so that safe commutation is achieved. This is not a desirable method since theinductors used are large. The switching time for each commutation is also greatly

increased which may cause control problems. Dead-time commutation uses a period

where no devices are gated, causing a momentary open circuit of the load. Snubbers or

clamping devices are then needed across the switch cells to provide a path for the loadcurrent. This method is undesirable since energy is lost during every commutation and the

bidirectional nature of the switch cells further complicates the snubber design. Theclamping devices and the power loss associated with them also results in increased

converter volume.

3.2.2 Current Direction Based Commutation

A more reliable method of current commutation, which obeys the rules, uses a four-stepcommutation strategy in which the direction of current flow through the commutation

cells can be controlled. To implement this strategy, the bidirectional switch cell must bedesigned in such a way as to allow the direction of the current flow in each switch cell to

be controlled. Fig. 9 shows a schematic of a two-phase to single-phase matrix converter,

representing the first two switches in the converter shown in Fig. 1. In steady state, bothof the devices in the active bidirectional switch cell are gated to allow both directions of

current flow. The following explanation assumes that the load current is in the direction

shown and that the upper bidirectional switch (SAa ) is closed. When a commutation to SBais required, the current direction is used to determine which device in the active switch is


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This method allows the current to commutate from one switch cell to another withoutcausing a line-to-line short circuit or a load open circuit. One advantage of all thesetechniques is that the switching losses in the silicon devices are reduced by 50% because

half of the commutation process is soft switching and, hence, this method is often called

semi-soft current commutation. One popular variation on this current commutation

concept is to only gate the conducting device in the active switch cell, which creates atwo-step current commutation strategy .

All the current commutation techniques in this category rely on knowledge of theoutput line current direction. This can be difficult to reliably determine in a switching

power converter, especially at low current levels in high-power applications wheretraditional current sensors such as Hall-effect probes are prone to producing uncertain

results. One method that has been used to avoid these potential hazard conditions is to

create a near-zero current zone where commutation is not allowed to take place, asshown for a two-step strategy in the state representation diagram in Fig. 11. However, this

method will give rise to control problems at low current levels and at startup. To avoid

these current measurement problems, a technique for using the voltage across the

bidirectional switch to determine the current direction has been developed. This methodallows very accurate current direction detection with no external sensors. Because of the

accuracy available using this method, a two-step commutation strategy can be employedwith deadtimes when the current changes direction, as shown in Fig. 12. This technique

has been coupled with the addition of intelligence at the gate drive level to allow eachgate drive to independently control the current commutation .

Fig. 11. Two-step semi-soft current commutation between two bidirectional switch

cells[1]

Timing Diagram

State Diagram


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Fig. 12. Two-step semi-soft current commutation with current direction detection

within the switch cell.[1]

3.2.3 Relative Voltage Magnitude Based Commutation

There have been two current commutation techniques proposed which use the relative

magnitudes of input voltages to calculate the required switching patterns. In the reductionto a two-phase to single-phase converter, these both look identical and resulting timing

and phase diagrams are shown in Fig. 13. The main difference between these methods

and the current direction based techniques is that freewheel paths are turned on in theinput voltage based methods. In Metzi current commutation, all the devices are closed

except those required to block the reverse voltage. This allows for relatively simplecommutation of the current between phases. In , only one extra device is closed and the

commutation process has to pass between the voltage of the opposite polarity during

every commutation, leading to higher switching losses. To successfully implement thistype of commutation, it is necessary to accurately measure the relative magnitudes of the

input voltages.

State Diagram

Timing Diagram


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Fig. 13. Voltage-based current commutation[1]

3.2.4 Soft-Switching Techniques

In many power converter circuits, the use of resonant switching techniques has been

proposed and investigated in order to reduce switching losses. In matrix converters,

resonant techniques have the additional benefit of solving the current commutationproblem. The techniques developed fall into two categories: resonant switch circuits and

auxiliary resonant circuits. All these circuits significantly increase the component count inthe matrix converter, increase the conduction losses, and most require modification to theconverter control algorithm to operate under all conditions.

Timing Diagram

State Diagram


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find a modulation matrix M(t)such that

......(2)

In (2), is the voltage gain between the output and input voltages.

There are two basic solutions as shown in equation 3 and 4.

The solution in (3) yields i=o, giving the same phase displacement at the input and

output ports, whereas the solution in (4) yields i=-o ,giving reversed phasedisplacement. Combining the two solutions provides the means for input displacement

factor control.This basic solution represents a direct transfer function approach and is characterized

by the fact that, during each switch sequence time (Tseq), the average output voltage isequal to the demand (target) voltage. For this to be possible, it is clear that the target

voltages must fit within the input voltage envelope for any output frequency. This leads to

a limitation on the maximum voltage ratio.

......... (3)........(3)

........(4)


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Fig. 14. Illustrating maximum voltage ratio of 50%[1]

4.2 Venturini Modulation Methods

The modulation solutions in (3) and (4) have a maximum voltage ratio (q) of 50% as

illustrated in Fig. 14. An improvement in the achievable voltage ratio to 3/2 (or 87%) ispossible by adding common-mode voltages to the target outputs as shown in (5).

The common-mode voltages have no effect on the output line-to-line voltages, but allowthe target outputs to fit within the input voltage envelope with a value of q up to 87% as

illustrated in Fig. 15.The common-mode voltages have no effect on the outputline-to-line

voltages, but allow the target outputs to fit within the input voltage envelope with a valueof up to 87% as illustrated in Fig. 15.

The improvement in voltage ratio is achieved by redistributing the null output states of

the converter (all output lines connected to the same input line) and is analogous to the

Vo=qVim

........(5)


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similar well-established technique in conventional dc-link PWM converters. It should benoted that a voltage ratio of 87% is the intrinsic maximum for any modulation methodwhere the target output voltage equals the mean output voltage during each switching

sequence.Venturini provides a rigorous proof of this fact.

Fig. 15 - Illustrating voltage ratio improvement to 87%[1]

The first method attributable to Venturini is defined by (3) and (4). However, calculating

the switch timings directly from these equations is cumbersome for a practical

implementation. They are more conveniently expressed directly in terms of the inputvoltages and the target output voltages (assuming unity displacement factor) in the form

of (6).

This method is of little practical significance because of the 50% voltage ratio limitation.

Venturinis optimum method employs the common-mode addition technique defined in (5)

to achieve a maximum voltage ratio of 87%. The formal statement of the algorithm,including displacement factor control, in Venturinis Algorithm is rather complex and

appears unsuited for real time implementation. In fact, if unity input displacement factor

is required, then the algorithm can be more simply stated in the form of (7)

.......(6)


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Note that, in (7), the target output voltages vj include the common-mode additiondefined in (5). Equation (7) provides a basis for real-time implementation of the optimum

amplitude Venturini method which is readily handled by processors up to sequence

(switching) frequencies of tens of kilohertz. Input displacement factor control can beintroduced by inserting a phase shift between the measured input voltages and the

voltages vkinserted into (7). However, like all other methods, displacement factor control

is at the expense of maximum voltage ratio.Fig.16 illustrates typical line to supply neutral output voltage and current waveforms

generated by the Venturini method.

Fig. 16. Typical waveforms. (a) Phase output voltage. (b) Load current[1]

......(7)


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5. Practical Issues

5.1 Input Filters

Filters must be used at the input of the matrix converters to reduce the switching

frequency harmonics present in the input current. The requirements for the filter are as

follows:1) to have a cutoff frequency lower than the switching frequency

of the converter;

2) to minimize its reactive power at the grid frequency;3) to minimize the volume and weight for capacitors and chokes;

4) to minimize the filter inductance voltage drop at rated current in order to avoid areduction in the voltage transfer ratio.

It must be noticed that this filter does not need to store energy coming from the load.Several filter configurations like simple LC and multistage LC have been investigated . It

has been shown that simple LC filtering, as shown in Fig. 17, is the best alternative

considering cost and size. The matrix converter is expected to be the pure siliconconverter, because it does not need large reactive elements to store energy.

Fig. 17. Matrix converter withLCfilter.[1]

However, a recent study revealed that a matrix converter of 4 kW needed a larger volumefor reactive components than a comparable dc-link inverter , although this solution had

not been optimized for volume. Some preliminary research works have been reported

concerning the size reduction of the input filter . Due to the LCconfiguration of the inputfilter, some problems appear during the power-up procedure of the matrix converter. It is

well known that an LC circuit can create overvoltage during transient operation. The


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connection of damping resistors, as shown in Fig. 17, to reduce overvoltages is proposed.The damping resistors are short circuited when the converter is running. The dampingresistors connected in parallel to the input reactors is proposed in Fig.18.

Fig. 18- L-C filter with parallel damping resistors[1]

5.2. Overvoltage Protection

In a matrix converter, overvoltages can appear from the input side, originated by lineperturbations. Also, dangerous overvoltages can appear from the output side, caused by

an overcurrent fault. When the switches are turned off, the current in the load is suddenly

interrupted. The energy stored in the motor inductance has to be discharged withoutcreating dangerous overvoltages.A clamp circuit, as shown in Fig. 19, is the most

common solution to avoid overvoltages coming from the grid and from the motor. Thisclamp configuration uses 12 fast-recovery diodes to connect the capacitor to the input and

output terminals. A new clamp configuration uses six diodes from the bidirectional

switches to reduce the extra diodes to six . A different overvoltage protection strategyreplaces the clamp by varistors connected at the input and at the output terminals, plus a

simple extra circuit to protect each IGBT . A controlled shutdown of the converter

without using a clamp has been proposed. This strategy uses controlled freewheelingstates to reduce the motor current to zero, avoiding the generation of overvoltages.


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Fig. 19. Matrix converter with clamp[1]

5.3 Ride-Through Capability

Ride-through capability is a desired characteristic in modern drives . A common solution

is to decelerate the drive during power loss, receiving energy from the load inertia to feedthe control electronics and to magnetize the motor. This is achieved by maintaining a

constant voltage in the dc-link capacitor. Matrix converters do not have a dc-linkcapacitor and, for this reason, the previously mentioned strategy cannot be used.

Fig. 20. Configuration to achieve ride-through capability[1]

Fig. 20 shows a configuration proposed to provide short-term ride-through capability to a

matrix converter using the clamp capacitor as the source for a switch-mode power supply

which feeds the converter control circuit. After detection of a perturbation in the powersupply, the motor is disconnected from the grid, but the switches of the matrix converter


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do not interruptthe motor currents. By applying the zero voltage vector (short circuit ofthe motor leads), the stator currents and the energystored in the leakage inductance increases. The disconnection of the active switches

originates the conduction of the clamp capacitor. This energy is then used to feed the

control circuits. A flux and speed observer is used to restart the drive from nonzero flux

and speed conditions in the shortest time.


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6. Simulation and Result

Fig.-Simulink Model for Venturini Algorithm Based Modulation of

Matrix Converter


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Fig.- Switching Scheme for Matrix Converter Using Nine

Bidirectional Switches


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Fig.- Modulation Technique(Using Venturini Algorithm)


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Generation of Gate Signal for Switch S11



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Sum of all the three duty cycles for input

phase"a"


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phase"b"


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phase"c"


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6.CONCLUSIONS

After two decades of research effort, several modulation and control methods have beendeveloped for the matrix converter, allowing the generation of sinusoidal input and output

currents, operating with unity power factor using standard processors. The most

important practical implementation problem in the matrix converter circuit, thecommutation problem between two controlled bidirectional switches, has been solved

with the development of highly intelligent multistep commutation strategies. The solution

to this problem has been made possible by using powerful digital devices that are nowreadily available in the market. Another important drawback that has been present in all

evaluations of matrix converters was the lack of a suitably packaged bidirectional switchand the large number of power semiconductors. This limitation has recently been

overcome with the introduction of power modules which include the complete power

circuit of the matrix converter. However, research work has shown that the matrixconverter is not a pure silicon converter and that passive elements in the form of input

filters are needed. More work must be done in order to optimize the size of these filters.

Twenty years ago, the matrix converter had the potential to be a superior converter interms of its performance. Now, the matrix converter faces a very strong competition from

the VSI with a three-phase active front end (AFE). This fully regenerative VSI-AFE

topology has similar operating characteristics of sinusoidal input and output currents andadjustable power factor. In addition, the technology is mature and well established in the

market. The real challenge for the matrix converter is to be accepted in the market. Inorder to achieve this goal, the matrix converter must overcome the VSI-AFE solution in

terms of costs, size, and reliability. The matrix converter offers many potential benefits to

the power converter industry. It will not be the best solution for all uses, but it offerssignificant advantages for many different applications.While, for many years, it seemed

that the matrix converter would be restricted to a small range of niche areas, the

commitment to invest in matrix converters from several large industrial drivesmanufacturers may see the start of an industrywide uptake of this technology.

Cutting-edge research in power converters is currently aimed at the use of wide-bandgap

materials such as gallium nitride (GaN) and silicon carbide (SiC). These materials offerpotential advantages over silicon devices, and research into the use of these devices in

prototype power converters is being reported.

Potential advantages include the following:

1) faster switchinglower switching loss;2) higher temperature operationhigher power density;

3) higher voltage structures.

Where these advantages may seem ideal and exactly what power electronics researchershave been looking for, considerable research needs to be carried out in order to realize

these potentials. The decrease in switching losses due to the promised increase inswitching speed cannot be presently implemented due to the associated problems caused


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to the EMI performance of the drive. Similarly, present packaging technology is thelimiting factor for the increased temperature operation of these new devices. A moreintegrated approach to power converter design will be needed in the future which takes

packaging, thermal management, circuit layout, and EMI performance into account at the

same time. In this way, optimized structures which minimize commutation paths and

conducted EMI while obtaining high-temperature operation will be attained.


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7. Future Work

Future work should focus on the improvement of the developed code to control theswitching of the converter switches to obtain a better performance of the direct matrix

converter. The design of accurate voltage measurement and high sensitivity current

direction detection circuits is necessary. Since safe commutation depends solely on eitherreliable detection of the load current direction or accurate voltage measurement. Besides,

improvement of both measurement circuits would solve the exiting problems.

Furthermore , future work could also focus on the evaluation of the proposed SV PWMcontrol strategy in the application of controlling the direct matrix converter topology. The

use of the SV PWM controlling mechanism offers full control of the generated outputvoltage and input current waveforms. An IGBT matrix module (FM35R12KE3) is

available now in some areas for research purpose. It is advisable to use an IGBT module

for constructing the direct matrix converter, because by doing so, the research will onlyemphasize on the development of the controlling algorithm.


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ac to ac 3-phase matrix converter

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