Acknowledgement

This work is part of the project performed by authors: Small Wind Turbine Optimized for Wind Low Speed Conditions

Pol-Nor/200957/47/2013

Aerodynamic Power extraction Control

It is important to limit the aerodynamic power extraction in

high wind speed conditions for safe operation. Some of availa-

ble control techniques are;

Furling Soft-stall control Passive pitching

Generator side Control

Main requirement of generator side control is controlling gen-

erator torque or speed in the optimum range. Two control

methods are available.

Direct torque control (DTC)

Field oriented control (FOC)

However FOC is widely used for the generator side control.

Three-phase dq transformation of stator current is required for

FOC. The PMSG generator torque control can be achieved by

controlling the Iq current component of the stator.

MPPT Control

The ultimate objective of wind turbine operation is to cap-

ture maximum available power from the wind turbine. There

are several control techniques available for this task;

Optimum tip speed control

Hill climbing and search

Power signal feed-back method

Fuzzy logic and Neural networks based control

Grid side Control

The main objective of grid side control is maintaining constant DC

voltage in the DC bus and providing reactive power requirement.

Most common method of controlling grid side converter is space

vector pulse width modulation (SVPWM). With this method, inde-

pendent active and reactive power control become possible.

The same method can be extended to use in both off-grid and grid-

connected applications.

Active and reactive Power Control

Voltage/frequency Droop control method can be used for active and

reactive power control.

Since grid-connected small wind generations are designed to feed

electricity to the distribution network, it is important to support

distribution network voltage changes and fault conditions for safe

operation.

Breaking chopper Control

The main objective of this control system is to control the DC

bus voltage in unstable operations of wind turbine.

When there is more energy feed from generator side than in-

jecting to the grid, the additional power can be dissipated

through a dummy resistor and it will help to keep constant

voltage in the DC bus.

Expected Project Works

Designing a sensor-less control system for estimating rotor speed, position and wind speed for maximum power point tracking.

Improve the generator side control system to capture energy at very low wind speeds and above rated wind speeds.

Include reactive power support and grid fault support which will improve the system as a reliable distributed generation system.

Development of circuits and Implementing the control algorithms .

Motivation

In modern renewable energy generation technologies, small wind turbines

have been focused as an attractive solution.

These micro generation wind turbines are suitable for both off-grid electric

requirements and grid-connected applications.

Small wind turbines give many advantages over large wind turbines;

Less environment impact

Improve the energy security via distributed generation etc.

The main design requirements in small wind turbine are;

Low cost

Improved reliability

Low noise level

High energy yield (especially at low and above rated wind speeds) etc.

To fulfil these requirements, optimum small wind turbine control system de-

signs are essential.

In this project we focus on control system optimization for horizontal axis

small wind turbines ( < 5 kW; PMSG ), which might be an ideal solution for

residential electricity requirements.

Control Systems for PMSG based Small Wind Turbines Jagath Sri Lal Senanayaka, Hamid Reza Karimi , Kjell G. Robbersmyr

Faculty of Engineering and Science, University of Agder, Grimstad, Norway

jagath.senanayaka@uia.no, hamid.r.karimi@uia.no, kjell.g.robbersmyr@uia.no

Generator Selection

Both induction generators and permanent magnet synchro-

nous generators (PMSG) can be used in small wind turbine

applications.

However PMSG are more attractive in modern applications

due to its advantages such as;

Less weight and simple construction

Gear-box can be eliminated with multi-pole arrange-

ment etc.

Wind-spot 3.5 kW system includes a sophisticated passive pitching and it can produce electricity in high wind conditions also.

WT6500 system has a specially designed ring-generator, which is placed in the outer ring of wind turbine and it can produce

electricity in low wind conditions.

Architectural Wind ; A small modular wind turbine solution

Whisper 500 , 3 kW Wind turbine is a highly reliable two-bladed wind turbine , which is very popular in US market

Architectural small, modular wind turbine solution by AeroVironment Inc. is an unique solution for residential applica-

tions.

Southwest Wind-power Whisper 500 ; 3 kW Wind turbine Honeywell WT6500; 1.5 kW Wind Turbine Wind spot 3.5 Kw Wind turbine

A block diagram of PMSG based synchronous generator is shown in above figure. There are six control systems in this small wind tur-

bine which have to be optimized .

Some commercially available small wind turbine designs are shown in following pictures.

According to their design requirements and intended applications, each design has at least one unique control feature .