Wind Energy Conversion System Using PMSG with T-Source Three Phase Matrix Converter

INTERNATIONAL JOURNAL FOR TRENDS IN ENGINEERING & TECHNOLOGY VOLUME 5 ISSUE 2 – MAY 2015 - ISSN: 2349 - 9303

Wind Energy Conversion System Using PMSG with T-Source Three Phase Matrix Converter K.T.Maheswari1

S.Viswanathan2

Assistant Professor, Department of Electrical and Electronics Engineering, Bannari Amman Institute of Technology Erode, India maheswarikt@gmail.com

PG Scholar, Department of Electrical and Electronics Engineering, Bannari Amman Institute of Technology Erode, India Viswa3e@gmail.com

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Abstract-This paper presents an analysis of a PMSG wind power system using T-Sourcethree phase matrix converter. PMSG using TSource three phase matrix converterhas advantages that it can provide any desired AC output voltage regardless of DC input with regulation in shoot-through time. In this control system T-Source capacitor voltage can be kept stable with variations in the shootthrough time, maximum power from the wind turbine to be delivered. Inaddition, of a new future, the converter employs a safecommutation strategy toconduct along a continuous current flow, which results in theelimination of voltage spikes on switches without the need for a snubber circuit. With the use of matrix converter the surely need forrectifier circuit and passive components to store energy arereduced. The MATLAB/Simulinkmodel of the overall system is carried out and theoretical wind energy conversion output load voltage calculations are madeand feasibility of the new topology has been verified and that theconverter can produce an output voltage and output current. This proposed method has greater efficiency and lower cost.

Index Terms- Matrix Converter (MC),Maximum Power Point Tracking (MPPT),Permanent Magnet Synchronous Generator (PMSG), T-Source Inverter (TSI), Z-Source Inverter (ZSI).

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1. INTRODUCTION

T

he renewable energy sources gained special importance over the years because of depletion of conventional energy sources. Wind energy is a very important renewable energy source and lots of technologies have been introduced to fetch power from wind energy.

PMSG wind power system using T-Source three phase matrix converter is an efficient way of harnessing power.Permanent magnet synchronous generator has numerous merits like high power factor, high efficiency, and low cost, gearless operations.

PMSG system includes diode rectifier, boost DC-DC converter and three phase inverter [4-6]. Control of inverter provides extracted power to the utility load side and boost converter is controlled for maximum power point tracking (MPPT).

This system becomes complex, expensive because of extra active devices and controls.T-Source inverter overcomes voltage limitations of traditional inverter voltage is boosted with single stage converter, both switches in the same inverter must turn ON in same time that is shoot-through state, due to this shoot-through state short circuit across any phases leg is allowed therefore reliability of system greatly improved [8].

Based on the advantages of T-Source three-phase matrix converters this paper presents application of T-Source inverter connected to wind power system which uses PMSG and generated power deliver to load.

Fig.1.General Block Diagram of the Proposed Topology

2. T-SOURCE INVERTER As with a conventional ZSI [1], the TSI can handle, shoot through states when both switches in the same phase leg are turned on.

The T-Source network is used instead of the LC-network for buck the output voltage by inserting shoot through states in the PWM [5-8].

TSI operates in two modes: 1) Shoot through Mode 2) Non Shoot through Mode.

2.1Shoot through Mode Fig.2 shows the equivalent circuit of T – source inverter in shoot through mode operation. This shoot through a zero state in traditional voltage source inverter. It can be obtained in three

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INTERNATIONAL JOURNAL FOR TRENDS IN ENGINEERING & TECHNOLOGY VOLUME 5 ISSUE 2 – MAY 2015 - ISSN: 2349 - 9303 different ways, such as shoot through via any one phase leg or combination of two phase leg. During this mode, diode is reverse biased, separating DC link from the AC line. A desired voltage can be maintained at the output by controlling the interval of shoot through state.

87 % for sinusoidal input and output waveforms, which can be improved. Further, matrix converter requires more semiconductor devices than a conventional AC-AC indirect power frequency converter. Since monolithic bi-directional switches are available, they are used for switching purposes of the converter.

3.1 Three Phase Matrix Converter The instantaneous power flow path does not have to equal power output. The main difference between the input and output power must be absorbed or delivered by an energy storage element within the converter.The matrix converter replaces the multiple conversion stages and the intermediate energy storage element by a single power conversion stage, and uses a matrix of semiconductor bidirectional switches connecting input and output terminals. With this general arrangement of switches, the power flow through the converter can reverse. Because of the absence of any energy storage element, the instantaneous power input must be equal to the power output, assuming ideal zero-loss switches.However, the reactive power input does not have to equal power output. It can be said again that the phase angle between the voltages and currents at the input can be controlled and does not have to be the same as at theoutput three phase matrix converter consists of only nine bi-directional switches.

Fig.2. Shoot ThroughMode

Thus the T–Source inverter highly improves the reliability of the inverter since short circuit across any phase leg is allowed and it cannot destroy the switches in the inverter.

2.2 Non – Shoot through Mode Fig.3. shows the equivalent circuit of TSI in Non – shoot through mode operation. In this mode, the inverter bridges operate in one of traditional active states, thus acting as a current source when viewed from T –source circuit [8]. During active mode, voltage impressed across load.

Fig.4.General Architecture of Three Phase Matrix Converter It has been arranged into three groups of three switches. Each group is connected to each phase of the output only. These arrangements of switches can connect any input phaseonly [2-4].

3.2 Commutation Methodsusing in Matrix Converter

Fig.3. Non-Shoot Through Mode

The commutation has to be actively controlled at all times. It is important that no two bidirectional switches are switched on at the same time. This results in short circuit at capacitor input and open circuit at inductive load occurs. There are two different types of commutation of the matrix converter available and it is explained in the following section.

The diodes conduct and carry current difference between the inductor current and input DC current. Note that both the inductors have an identical current because of coupled inductors.

The T-Source network can operate in six possible states, in which three states are desired while the other three are undesirable. And the undesirable states can be avoided by choosing appropriate values of the inductors and capacitors of the impedance network.

3.2.1 Dead Time Commutation of matrix converter

3. THREE-PHASE MATRIX CONVERTER This type of commutation method is used in the inverter side only provided. It means that load current freewheel to throw antiparallel diode during the dead time period. In a case of the matrix converter dead time commutation method is useless. It results in the open circuit at the load side only. Then forced spike only occurs across the switches. To avoid this snubber clamping devices are provided this method. This is a power path to the load current during the dead time and hence the design of snubber circuit is more difficult[10].

The important advantage of matrix converter is elimination of theDC link filter in circuits. Zero switching loss devices can transfer input power to output power without any other loss. But practically it does not exist. The switching frequency only decides THD of the converter. Maximum power transfer to the load is decided by the nature of the control algorithm. Matrix converter has a maximum input, output voltage transfer ratio limited to 60-

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INTERNATIONAL JOURNAL FOR TRENDS IN ENGINEERING & TECHNOLOGY VOLUME 5 ISSUE 2 – MAY 2015 - ISSN: 2349 - 9303 đ?‘‰đ?‘Žđ?‘? = đ?‘Œ. đ?‘‹ 3.2.2 Current Commutation Based on Multiple Steps using matrix converter

The peak output phase voltage can be controlled both by adjusting the modulation index or shoot-though time.

This type of commutation uses bidirectional switches. These are more reliable in current commutation and obey the basic rules. It can be able to control the direction of the current. This strategy is essential in case of controlled current flow. This commutation technique relies on knowledge of the output current direction.

This current direction can be difficult to reliably determine and allow current levels in high power drives.

To avoid this problem a technique of using the voltage across the bi-directional switch to determine the current direction has been developed. This technique provides reliable, current commutation using an intelligent gate drive circuit which controls the firing of the IGBTs and detects the direction of current flow within the bidirectional switch cell. The current direction information calculated by the active gate drive is passed to all the other gate drivers on the same output leg.

In this way all the gate drivers contribute to operate a safe commutation. In matrix converter commutation issue is taken care by Matlab simulation. Forced commutation is an employed throughout the process.

4. SIMULATION RESULTS 4.1 The Proposed Simulink Model of Three Phase Matrix Converter

Fig.5.Simulink /Matlab simulation of Three Phase Matrix Converter

3.3 PMSG Using Wind Energy Conversion System

4.2 Simulink Results for Output Voltage waveform for three phase matrix converter

The PMSG wind power system with T-Source three phase matrix converter based load side connected.This configuration includes a PMSG is connected to three phase diode rectifier with the input capacitors (CA, CB and CC), a T-Source network, and inverter system connected to load side [3]. The purpose of the input capacitors is to serve as the DC source feeding the T-Source network. The voltage of the generator fed to the T-Source inverter varies according to the generator speed[6-7-9].

It is assumed that the DC voltage fed to the T-Source inverter where VLL is the line to line voltage of the generator.

3 3 đ?‘‰đ?‘‘đ?‘? = đ?‘‰đ??żđ??ż đ?œ‹ In boost operating mode that is in shoot through state, the peak DC link voltage across the inverter bridge is expressed as

Fig.6. Simulink /Matlab simulation results, Output Voltage waveform for three phase matrix converter

đ?‘‰đ?‘– = đ?‘‹. đ?‘‰đ?‘‘đ?‘?

4.3 Simulink Results for Output Current waveform for three phase matrix converter

Where VDC is the source voltage and X is the boost factor that is determined by đ?‘‹=

đ?‘‰đ?‘‘đ?‘?

2

đ?‘Ą ≼1 đ?‘Ą − 2đ?‘Ąđ?‘œ

Wheretois the shoot-through time interval over a switching cycle T. The capacitors voltage can be expressed as bellow đ?‘‰đ?‘? =

đ?‘Ą − đ?‘Ąđ?‘œ đ?‘‰đ?‘‘đ?‘? ≼ đ?‘‰đ?‘‘đ?‘? đ?‘Ą − 2đ?‘Ąđ?‘œ

The capacitor voltage can be boosted by adjusting the shootthrough time.

The output peak phase voltage can be expressed as

Fig.7. Simulink /Matlab simulation results, Output Current waveform for three phase matrix converter

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INTERNATIONAL JOURNAL FOR TRENDS IN ENGINEERING & TECHNOLOGY VOLUME 5 ISSUE 2 – MAY 2015 - ISSN: 2349 - 9303 Three Phase Matrix Converter 4.4 T-Source Three Phase Matrix Converter Generation

Pwm Pulse 4.8 Simulink Results for Output Voltage waveform for PMSG Using T-Source Three Phase Matrix Converter

Fig.8.Simulink Model of T-Source Three Phase Matrix Converter Pwm Pulse Generation Fig.12. Simulink /Matlab simulation results, Output Voltage waveform for PMSG Using T-Source Three Phase Matrix Converter

4.5 PWM Pulse Generation

4.9 Simulink Results for Output Current waveform for PMSG Using T-Source Three Phase Matrix Converter

Fig.9. Simulink /Matlab simulation results, Sinusoidal Pwm Pulse Generation 4.6 Comparison of Carrier and Reference Waveforms Fig.13. Simulink /Matlab simulation results, Output Current waveform for PMSG Using T-Source Three Phase Matrix Converter

5. CONCLUSION In this paper, the PMSG wind power system connected to load using T-source three phasematrix convertersare proposed. The proposed system worked effectively with the input DC voltage lower than the load level voltage. The converter employs a safecommutation strategy toconduct along a continuous current flow, which results in theelimination of voltage spikes on switches without the need for a snubber circuit. The proposed system extracted the power from wind turbine and delivered high quality voltage and current into the load side calculated by using MATLAB/Simulink. The proposed T-source three matrix convertersare more efficient, cost effective and have high performance.

Fig.10.Simulink Model of Carrier and Reference Waveforms 4.7 The Proposed Simulink Model of PMSG Using T-Source Three Phase Matrix Converter

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Fig 11.Simulink /Matlab simulation of PMSG Using T-Source

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AUTHOR PROFILE:  K.T.Maheswari is currently working as Assistant Professor in Bannari Amman Institute of technology,India,Ph:9788459307, E-mail: maheswarikt@gmail.com  S.Viswanathan is currently pursuing Master of Engineering in Bannari Amman Institute of Technology, India,Ph:9585308233, E-mail:viswa3e@gmail.com

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