Development of AC to AC Direct Matrix Converter

Project Title

Development of AC to AC Direct Matrix Converter

Project Area of Specialization Electrical/Electronic EngineeringProject Summary

Matrix Converter Provide three phase variable voltage and frequency from fixed three phase input supply using single stage conversion principle. There is no need of intermediate DC link which decrease the cost and size of this converter. Three phase output is synthesized by three phase input through nine bidirectional switches. The gate signal of power switches is produced by different pulse width modulation techniques. We are using Space Vector Pulse Width Modulation (SVPWM) technique for generating gate pulses of bidirectional switches because it eliminate the switches losses by selecting the proper switching states. The nine bidirectional switches are arranged so that you can connect any of the input phases to any of the output phases. Space Vector Modulation technique can be seen as the best solution for achieving the maximum voltage transfer ratio, improving the switching pattern, the output voltage and less harmonics of input current.This method takes sinusoidal input and give us the sinusoidal output waveforms, improve the output control performance in motor drive applications. Direct matrix converter has several applications: variable frequency drive, direct torque control of induction motor and permanent synchronous magnet motor, speed control of AC machines, wind generation system, pumps, fans,   paper and cloth mills, elevators, electric vehicles, subway transport, home appliances, steel and cement mills, etc.

Project Objectives

    Matrix Converter (MC) provide variable voltage and variable frequency at output, which we want at output according to our demand. As the demand of energy saving is an important part in this era. Inverters are using in a wide range in many applications. Demand of low cast, smaller size and high efficiency will continue to further expand the range of inverter applications. Due to these things the direct matrix converter is getting more attention and is emerging as a modern energy converter. As conventional converter which consists of first rectification AC-DC and then inversion steps DC-AC, which are commonly using in industries for variable speed drives, have many drawbacks as they a bulky electrolytic capacitor which have limited life time. These conventional converter have also large harmonic distortions in output voltage and current. But matrix converter has many attractive features such as it has simple and compact power circuit due to the absence of bulky electrolytic capacitors. MC also has sinusoidal input and output currents, controllable input power factor with any load, bidirectional power flow due to the use of bidirectional switches, long lifetime due to the absence of electrolytic capacitor and high reliability. A device that could conduct in both directions is commercially not available. So, its main building block is bidirectional switches which connect directly the three phase input to three phase output. We can get desired variable output voltage and frequency from constant input supply using direct matrix converter. As matrix converter consist of bidirectional switches, these switches are controlled with modulating signals and by controlling these modulating signals we can get desirable output.

                                                                      

                                                                                                                                                                                              Figure 2:Common Emitter Arrangement

  Figure 1: Three Phase to Three Phase Direct Matrix Converter Topology                                                                       Source: A THREE-PHASE AC/AC MATRIX CONVERTER SYSTEM by
                                                                                                                                                                                                            GEBREGERGIS, ABRAHAM GEBREHIWET

Project Implementation Method

   As direct Matrix Converter (MC) consists of nine bidirectional switches and 2­­9 (512) different switching configuration are formed in it. MC supply the controllable voltage and frequency to the inductive load  output directly and due to the following two rules only 27 switching configuration are useful in direct matrix converter implementation:

1. Avoid from line to line short circuit at input.
2. Avoid from open circuit at output, to avoid from current interruption.

                                                         

                                                        Figure: Three Phase to Three Phase Direct Matrix Converter Topology

 

                                                            (1)

                                                           (2)                                         

Where VA, VB and VC are the output phase voltages, and ia, ib and ic are the input currents. These equations, Eq.1 and Eq.2 shows that output voltage and input current can be controlled by controlling switching matrix.

                                       Sxy (t) =   , x ? {a, b, c} and y ? {A, B, C}                                        (3)

 Here 1 represent that switch Sxy is closed and 0 represent that switch is open.

                                      Sax + Sbx + Scx = 1,   x = {A, B, C}                                         (4)

  Equation 4 show that only one switch must be on in an output branch. Otherwise, over voltage problem would occur in the converter due to the inductive load. If all switches are left open in an output branch current would interrupt.

Matrix converter is controlled by many modulation techniques to produce the user required output voltage and frequency. For this purpose a specific set of switches is selected at an appropriate interval. In this project we are using Direct Space Vector Pulse Width Modulation (SVPWM) Technique.

 As in matrix converter there are 27 different switching configurations, but in modern SVPWM only 21 configurations of switches are used as shown in Table 1. Switching configurations are divided into 3 groups as follow:

  Group-1:  In this group 18 switching configurations in which two phase of output are connected to the same input phase and produce output voltage and input current with variable amplitude vectors with fixed direction. This configuration is called “active configurations”.

  Group-2:  In this group all the output phases are connected to the same input phase and this configuration known as “freewheel configuration.

  Group-3:  In this group all the output phases are connected to different input phase and these configurations give rotating vector of voltage and current with fixed amplitude.

                                  

                                                     

                                         Figure: Switching configurations of the matrix converter used in the proposed DTC control scheme.

                                         Source of above table: @inproceedings{2002DirectTC, title={Direct Torque Control using Matrix Converters},author={}, year={2002}}

Benefits of the Project

  The advantages of this converter over indirect conventional converters are: power factor regulation, sinusoidal current consumption, sinusoidal output voltage with low harmonics and high efficiency. But matrix converter has many attractive features such as it has simple and compact power circuit due to the absence of bulky electrolytic capacitors. MC also has sinusoidal input and output currents, controllable input power factor with any load, bidirectional power flow due to the use of bidirectional switches, long lifetime due to the absence of electrolytic capacitor and high reliability. We can get desired variable output voltage and frequency from constant input supply using direct matrix converter.

• Our project is use for desire variable frequency and variable voltage
• We will use MC for controlling speed of different devices e.g. Induction Motor and water pump.
• We are making this converter for reducing the cost. Common converters have big size but our converter size will be small as compared to Common converter.

Applications:

This project has many applications and some of them are described below.

• Wind Energy Conversion System  

In wind Energy Conversion System (WECS) we produce energy by wind. Sometimes wind is too fast or very slow, these conditions are abnormal Conditions. But we need fix voltages and frequencies for our work. For this purpose we use matrix converter for getting our desire results of voltage and frequency.

• Utility power supply

In this application MC is connected with variable speed diesel generator for useful supply. In this we get high performance power in power supply. In this we use programmable ac source and supply units. This MC based mobile AC supply units serve in aircrafts. 

• AC Motor Drive

For high inertia systems, there is required dynamic braking and VSI-based system required rectifier stages for supplying Dc supply and braking chopper to absorb kinetic energy. But in our MC bi-directional switches are used, so there is no need of braking chopper.

• Renewable energy generation

In renewable power generation, in wind turbine, MC employed to adjust performance of wind generator and get maximum power, thus better efficiency. These were the main applications, MC is used in many things which are given below:  

• Micro-grids
• Submarines
• Induction Heating etc.

Technical Details of Final Deliverable

 

  The converter directly links three phase (3- Ø) input AC lines to three phase output AC loads through switching devices. A modulation technique is developed to synthesize three sinusoidal output waveforms with variable voltage and variable frequency from input AC voltages.

The system consists of the following parts: 

•  A small input filter to lower the input current ripple 
• · A gate drive circuit that drives the power converter's IGBT switch 
• · A main power converter where the actual switching operation is performed 
• · A clamp circuit that protects the power converter switches from damage when a failure occurs.

Input Filter:

The input filter circuit, which is designed with minimum energy on the reactive element to reduce the input ripples. A LC series circuit is the simplest form of filter topology, which can be designed to fit the matrix converter requirement. The circuit in the LC series provides all the required characters from a filter circuit.

                                                                                                         Figure: Input Filter

Power Converter Circuit:

Consisting of bidirectional switches as matrix converter. Popular Emitter and popular collector configurations require complete control of current direction at all times through the bi-directional switch, the power loss in the switching system is lower. Either of these structures can be used to construct the topology matrix converter main power converter circuit. Since the Common Emitter arrangement has the following advantages over the Common Collector, access to all IGBT terminals is possible and suitable for VCE monitoring. To handle this input power is needed the IGBT switching system selected to create the power converter of the direct matrix converter circuit. Selection depends on the maximum input voltage applied to the switching device terminal, as well as the maximum output  current passing through the switching system.circuit.Selection depends on the maximum input voltage applied to the switching device terminal, as well as the maximum output current passing through the switching system.

Gate Drive Circuit:

The function of the gate-driver circuit is to generate high current output to drive the IGBT switches of the main power converter circuit.

Protection Circuit:

When an over-voltage or open circuit occurs, the direct matrix converter circuit needs a safety. The engineered circuit prevents the IGBT switches from being damaged during a sudden open circuit at both sides of the converter terminal due to an error PWM signal generation or an overcurrent failure detected by the overcurrent protection circuit.

Final Deliverable of the Project HW/SW integrated systemCore Industry Energy Other Industries Education , Manufacturing Core Technology OthersOther TechnologiesSustainable Development Goals Decent Work and Economic Growth, Industry, Innovation and InfrastructureRequired Resources

Item Name	Type	No. of Units	Per Unit Cost (in Rs)	Total (in Rs)
			Total in (Rs)	16215
IGBTs	Equipment	25	350	8750
Optocoupler	Equipment	13	100	1300
Arduino Mega	Equipment	1	1500	1500
Resisters	Equipment	35	5	175
Capacitors	Equipment	35	6	210
Diode	Equipment	20	10	200
PCB	Equipment	1	720	720
Travelling Cost	Miscellaneous	2	1500	3000
Heat Sink	Equipment	18	20	360