SMALL WIND TURBINE PMSG GENERATION

SYSTEM

University of New Brunswick

May 19, 2006

Sustainable Power Research Group

Gene Z. Guo

R&D of distributed power generation (DG) systems is becoming more and more popular nowadays because of 1.     Increasing demand of electric generation2.     Various advantages of DG system, such as environmental-friend, short construct period, etc.3.     and the development of related theory and technology.

Wind power generation systems are one of the most important R&D and application of the DG systems.

Direct-drive, variable frequency PMSG grid-connected wind generation system is playing an important role in the small wind power applications.

Introduction

A 3kW wind power generation system is presented, the system includes

Whisper 175 wind turbine from Southwest windpower

 3kW DSP-controlled single phase grid-connected IGBT inverter

Three key issues are studied to improve the performance

   Inverter current THD reduction

Improved predictive current control algorithm is presented

    Inverter Noise reduction

Improved PWM strategy is applied

     Maximum wind power extraction of the inverter

Fuzzy-logic-based MPPT strategy is employed

Rotor Diameter: 15 ft. (4.5m)

Weight: 155 lbs (70kg)

Mount: 5” schedule 40 (12.7cm)

Start-up wind speed: 7.5 mph (3.4m/s)

Voltage: 0~440Vac

Rated Power: 3000 watts at 24mph (10.5m/s)

Peak Power: 3200 watts at 27mph (12m/s)

Turbine Controller: EZ-Wire Wind & Solar Hybrid

Blades (three): Carbon reinforced fiberglass

Kilowatt hours per month: 538 kWh/mo @12mph (5.4m/s)

Warranty: 2 Year Limited Warranty or 5 year Extended Warranty Option

Whisper 175 Wing Turbine Specifications

Southwest Windpower

Improved predictive current controler

Block diagram of VSWT generation system

PMSGSingle-phase Inverter

Grid

VSWT

Current Controller

Power Converter

3-phase input

single-phase output,

grid-connected,

DSP controlled

Voltage Source

The key to reduce current THD is to slect suitable current controller

Features of inverter:

Generally, the inverter current controllers can be classified as:

Hysteresis Current Controller

Simple and robust

Switching frequency depends on the load parameters

Current THD is high

Ramp Comparison Current Controller

Switching frequency is limited to that of the triangular waveform

Produced current harmonics are defined at a fixed frequency

Inherent phase and amplitude errors arise, even in the steady state

Predictive Current Controllers.

Offers potential for achieving more precise current control with minimum distortion and harmonic noise

Increase the computation effort and parameters dependency

Single-Phase Grid-Connected Inverter Topology

dt

diLVV load

gridop

Standard Predictive Control Algorithm

period

loadloadgrid_avop_av T

][]1[][

nInILnVnV

Discrete form:

Govern Eq.:

Control target: ]1[ref nI =Iload[n+1]

period

loadrefgrid_avop_av T

][]1[][

nInILnVnV

Therefore:

period

loadref_gridgridop_av T

]1[]1[]1[]2[2]1[4][

nInILnVnVnVnV avop

After formule manipulation

Improved Predictive Current Algorithm

TD:Total delay

Standard predictive current algorithm is of poor robustness

The sampling point is moved as shown above]1[5.0][5.1][_ nVnVnV gridgridavgrid

Govern Eq.:period

loadrefgridgridop_av T

][]1[]1[5.0][5.1][

nInILnVnVnV

An Improved PWM Strategy for Inverter Noise Reduction

Inverter noise mainly comes from AC filter inductor, depends on the harmonic current frequency passing the inductor, furthermore, PWM carrier frequency

Noise can be reduced through control the current harmonic frequency of inductor, higher or lower than the hearable spectrum

Limited to present IGBT technology and considering of the losses and temperature rise, the switching frequency of IGBT is set as 10kHz in this project

Switching PWM Scheme

gridOL VV

dt

diL

Conventional PWM Strategy

Improved PWM Strategy

Improved PWM Strategy PWM Scheme Generation in DSP

Compared with the conventional one, the current harmonics of the new is doubled to 20kHz, prevent the hearable noise

By splitting the pulse width in a PWM period, the switching frequency keep same: 10kHz,but the noise and current THD is significantly improved

TEST RESULTS

In order to extract maximum power from the wind turbine, the Maximum Power Point Tracking (MPPT) method should be employed. In this project, a fuzzy-logic-based MPPT algorithm is presented and applied.

In this method, the dc-link voltage and current, Vdc and Idc, are sampled as the power feedback for the

inverter controller, and the Vdc reference signal is

updated in real time using a hill-climbing searching (HCS) method so as to lead the system to its optimal operation point.

The FLC is robust and the searching for optimal Vdc

is fast and accurate.

MPPT Based on Fuzzy-logic Algorithm

Power circuit of single-phase grid-connected inverter and its control block diagram

IL

Vdc

HCS

Idc

FLC CCVdc

* Idm

PWM4MPPT

V

T1

T2

T3

T4

L

Cdc C

From Generator

240V60HzGrid

Diode Rectifier IGBT Inverter Bridge

DB

Simulation model of VSWT generation system in Matlab

scope1

scope

u

Wind Speed

u

Pload

w

Cp

WInd Turbine

Pload

Vdc

Idm

Vav

Vdc*

Pav

MPPT

Vdc

Idm

Pout

Idc

Inverter & Grid

w

idcVdc

Generator& Rectifier

0 100 200 300 400 500 6000

3

6

9

12

win

d sp

eed

(m/s

)

0 100 200 300 400 500 6000

200

400

Vdc

(V)

0 100 200 300 400 500 6000

5

10

Pou

t (kW

)

0 100 200 300 400 500 6000

0.2

0.4

time (s)

Cp

0 100 200 300 400 500 6000

5

10

wind

spe

ed (m

/s)

0 100 200 300 400 500 6000

200

400

Vdc

(V)

0 100 200 300 400 500 6000

5

10

Pout

(kW

)

0 100 200 300 400 500 6000

0.10.20.30.40.5

time (s)

Cp

Simulation results with step change in wind speed

Simulation results with random wind speed

Inverter Construction & Test Results

Power circuit schematic diagram

 

Main LoopModule

Main LoopModule

SystemProtection

SystemProtection

PWM ControlPWM Control

Interrupt ServingModule

Interrupt ServingModule

Input & Output Control

Input & Output Control

System Initialization

System Initialization

Start/Stop P/BStart/Stop P/BLCD DisplayLCD Display

Relays Control 

Relays Control 

O/P Power ControlO/P Power Control

ADC ISRADC ISR

CAP3 ISRCAP3 ISR

Zero-crossing Detection

Zero-crossing Detection

PWM Underflow ISR Serve

PWM Underflow ISR Serve

Timers SynchronizationTimers SynchronizationStartStart

 

PWM Underflow ISR Serve

PWM Underflow ISR Serve

Timers SynchronizationTimers Synchronization

Software block diagram of the inverter

ACKNOWLEDGEMENT

The research group wish to thank the Atlantic Innovation Fund (AIF) for its support to this research project