C u r t i n & P U C R S Harmonic Mitigation in Wind Turbine Energy Conversion Systems Fernando Soares dos Reis, Pontifical Catholic University of Rio Grande do Sul Syed Islam and Kelvin Tan, Curtin University of Technology

C u r t i n & P U C R S Table of Contents  Brazil  PUCRS  Introduction  Objectives  Power Quality  Harmonic Characterization  The Harmonic Mitigation Schemes  Power Losses  Conclusions

C u r t i n & P U C R S Where is PUCRS? PORTO ALEGRE PERTH In Brazil! Did you know that Brazil is 5 th biggest country in the world after Russia, China, Canada and USA, with km 2. Our population is about 180 Million of habitants.

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C u r t i n & P U C R S Table of Contents  Brazil  PUCRS  Introduction

C u r t i n & P U C R S INTRODUCTION Permanent magnet synchronous generators (PMSG) wind energy conversion system (WECS) using variable speed operation is being used more frequently in wind turbine application. Variable speed systems have several advantages over the traditional method of operating wind turbines, such as the reduction of mechanical stress and an increase in energy capture. To allow the variable speed operation of the PMSG WECS a conventional three-phase bridge rectifier (BR) with a bulky capacitor associated with voltage source current controlled inverter (VS-CCI) is used.Permanent magnet synchronous generators (PMSG) wind energy conversion system (WECS) using variable speed operation is being used more frequently in wind turbine application. Variable speed systems have several advantages over the traditional method of operating wind turbines, such as the reduction of mechanical stress and an increase in energy capture. To allow the variable speed operation of the PMSG WECS a conventional three-phase bridge rectifier (BR) with a bulky capacitor associated with voltage source current controlled inverter (VS-CCI) is used.

C u r t i n & P U C R S INTRODUCTION This simple scheme introduces a high intensity low frequency current harmonic content into the PMSG and consequently increases the total loses in it. Subsequently, decreases the power capability of the system. This work presents a comparative simulation study between two different approaches applied to harmonic mitigation on PMSG WECS. The studied techniques are: a) harmonic trap filters (HTF), b) single-switch three-phase boost rectifier (PFC) and c) PWM Boost Rectifier.This simple scheme introduces a high intensity low frequency current harmonic content into the PMSG and consequently increases the total loses in it. Subsequently, decreases the power capability of the system. This work presents a comparative simulation study between two different approaches applied to harmonic mitigation on PMSG WECS. The studied techniques are: a) harmonic trap filters (HTF), b) single-switch three-phase boost rectifier (PFC) and c) PWM Boost Rectifier.

C u r t i n & P U C R S 2.4 MW Power Plant in the Northest

C u r t i n & P U C R S 4.8 MW Power Plant in the South (8 x 600 kW)

C u r t i n & P U C R S 5.0 MW Power Plant in the Northest 10 x 500 kW

C u r t i n & P U C R S WECS

Line-commutated inverter

C u r t i n & P U C R S Current controlled inverter

C u r t i n & P U C R S Table of Contents  Brazil  PUCRS  Introduction  Objectives

C u r t i n & P U C R S AC-DC Conversion

C u r t i n & P U C R S Table of Contents  Brazil  PUCRS  Introduction  Objectives  Power Quality

C u r t i n & P U C R S Power Quality The power quality concepts are well established and Widely applied in the relationship between utility and consumer;The power quality concepts are well established and Widely applied in the relationship between utility and consumer; Because it allows the maximization of the energy resources;Because it allows the maximization of the energy resources; But these concepts were not normally applied to WECS once there are studies showing that the system efficiency is practically the some with or without harmonics in the PMSG.But these concepts were not normally applied to WECS once there are studies showing that the system efficiency is practically the some with or without harmonics in the PMSG.

C u r t i n & P U C R S Table of Contents  Brazil  PUCRS  Introduction  Objectives  Power Quality  Harmonic Characterization

C u r t i n & P U C R S Harmonic Characterization

C u r t i n & P U C R S Harmonic Characterization

C u r t i n & P U C R S

Table of Contents  Brazil  PUCRS  Introduction  Objectives  Power Quality  Harmonic Characterization  The Harmonic Mitigation Schemes

C u r t i n & P U C R S The Harmonic Mitigation Schemes The Harmonic Mitigation Schemes  Passive Harmonic Trap Filters (HTF)  Single-Switch Three-Phase Boost Rectifier  Three-Phase Boost type PWM Rectifier (AC-DC converter) Objectives  Active Power Filter

C u r t i n & P U C R S Passive Harmonic Trap Filters (HTF)

C u r t i n & P U C R S Harmonic Trap Filters

C u r t i n & P U C R S Using HTF for the 5 th and 7 th harmonic

C u r t i n & P U C R S Using HTF for the 5 th and 7 th harmonic PMSG output current

C u r t i n & P U C R S Using HTF for the 5 th and 7 th harmonic PMSG output voltage

C u r t i n & P U C R S

Single-Switch Three-Phase Boost Rectifier

C u r t i n & P U C R S Single-Switch Three-Phase Boost Rectifier

C u r t i n & P U C R S Three-phase PMSG output currents

C u r t i n & P U C R S Three-phase bridge rectifier input currents

C u r t i n & P U C R S PMSG output current

C u r t i n & P U C R S PMSG output voltage

C u r t i n & P U C R S Three-Phase Boost type PWM Rectifier

C u r t i n & P U C R S Three-Phase Boost type PWM Rectifier

C u r t i n & P U C R S Three-Phase Boost type PWM Rectifier IGBT + Diode current

C u r t i n & P U C R S Three-Phase Boost type PWM Rectifier input currents

C u r t i n & P U C R S Three-Phase Boost type PWM Rectifier line to line voltage

C u r t i n & P U C R S PMSG output current

C u r t i n & P U C R S PMSG output voltage

C u r t i n & P U C R S Table of Contents  Brazil  PUCRS  Introduction  Objectives  Power Quality  Harmonic Characterization  The Harmonic Mitigation Schemes  Power Losses

C u r t i n & P U C R S Power Losses  PMSG losses  Bridge Rectifier Losses  Harmonic Trap Filter Losses  Semiconductor Losses  Mechanical losses

C u r t i n & P U C R S PMSG losses reference circuit

C u r t i n & P U C R S PMSG losses

C u r t i n & P U C R S PMSG losses

C u r t i n & P U C R S Conclusions In this work three well-known harmonic mitigation solutions were applied to PMSG WECS AC to DC conversion. They were the HTF, the PFC and the PWM. Harmonic trap filters are easily implemented by passive components but they are normally implemented with bulk components.In this work three well-known harmonic mitigation solutions were applied to PMSG WECS AC to DC conversion. They were the HTF, the PFC and the PWM. Harmonic trap filters are easily implemented by passive components but they are normally implemented with bulk components.

C u r t i n & P U C R S Conclusions Notwithstanding the HTF had presented the good THD results they are not the best solution once they are a matched solution for a specific operation point (wind speed and output power). The losses study also has demonstrated that the PMSG efficiency (η) remains practically constant and the system η is the lowest when the HTF are used.Notwithstanding the HTF had presented the good THD results they are not the best solution once they are a matched solution for a specific operation point (wind speed and output power). The losses study also has demonstrated that the PMSG efficiency (η) remains practically constant and the system η is the lowest when the HTF are used.

C u r t i n & P U C R S Conclusions For these reasons, it is not a recommended way out to obtain harmonic mitigation on PMSG WECS. On the other hand, the single-switch three-phase boost rectifier has presented encouraged results. Such as: low current and voltage THD, simple power topology and control circuit, can work in all wind conditions and presents a real reduction of the PMSG total losses.For these reasons, it is not a recommended way out to obtain harmonic mitigation on PMSG WECS. On the other hand, the single-switch three-phase boost rectifier has presented encouraged results. Such as: low current and voltage THD, simple power topology and control circuit, can work in all wind conditions and presents a real reduction of the PMSG total losses.

C u r t i n & P U C R S Conclusions Which allow expecting an increasing in the PMSG lifetime without reduction of the power capability. The main drawbacks of this topology are a) the conduction losses in the BR diodes and switch Q1 since the high RMS current value caused by the DCM operation and b) the high output voltage 1 kV. Both problems could be minimized using proper diodes and switch like IGBT.Which allow expecting an increasing in the PMSG lifetime without reduction of the power capability. The main drawbacks of this topology are a) the conduction losses in the BR diodes and switch Q1 since the high RMS current value caused by the DCM operation and b) the high output voltage 1 kV. Both problems could be minimized using proper diodes and switch like IGBT.

C u r t i n & P U C R S Conclusions With the actual technology these problems could be easily solved. The PWM rectifier was studied once if this complex converter is possible to obtain ideal PF and THD. But the losses study has show results very closed to that obtained with the Single Switch Boost Converter. The main advantage is that with this converter is possible to work with output voltages around 600V in spite of 1000V.With the actual technology these problems could be easily solved. The PWM rectifier was studied once if this complex converter is possible to obtain ideal PF and THD. But the losses study has show results very closed to that obtained with the Single Switch Boost Converter. The main advantage is that with this converter is possible to work with output voltages around 600V in spite of 1000V.

C u r t i n & P U C R S THANK YOU It was a pleasure be here I have enjoy the last six months as the bets in work life.It was a pleasure be here I have enjoy the last six months as the bets in work life. Special thanks to: Professor Syed Islam and all staff members.Special thanks to: Professor Syed Islam and all staff members. I hope see you again here or in BRAZIL.I hope see you again here or in BRAZIL.