Demonstration of wind power generation

Summary

This video covers a detailed demonstration of wind power generation, focusing on the doubly fed induction generator (DFIG) setup used in modern wind turbines. It explains how wind energy is converted into electrical power through turbines, generators, and power converters. Key topics include the operating modes of DFIG (sub-synchronous, synchronous, and super-synchronous), the control strategies using rotor side converters (RSC) and grid side converters (GSC), and how power flows from the rotor and stator to the grid. The hardware setup and software integration are also highlighted, showing how wind emulation is achieved in a lab environment.

Takeaways

• 🌬️ Wind power generation involves capturing kinetic energy through wind turbines, which is converted to electrical energy via a gearbox, generator, and transformer.
• 🔋 The doubly fed induction generator (DFIG) is a partial variable wind system, known for its cost-effectiveness due to scaled-down converter sizes.
• ⚡ DFIG wind systems can inject power into the grid across a wide range of wind speeds, maintaining grid stability.
• 🔄 DFIG operates in three modes: sub-synchronous, synchronous, and super-synchronous, depending on the rotor speed relative to the grid frequency.
• 🌀 The rotor speed varies with wind speed, from sub-synchronous speeds in low wind to super-synchronous speeds in high wind.
• 📉 During sub-synchronous mode, the rotor draws power from the grid, while during super-synchronous mode, excess power is fed back to the grid.
• 🛠️ The DFIG hardware setup includes a wind emulator, slip ring induction motor, and back-to-back voltage source converters.
• 🔧 A DC motor emulates wind conditions and is controlled via a chopper, while buck converters manage the power flow.
• 🎛️ FPGA controllers, specifically the vivect FPGA, regulate the system, monitoring voltages, currents, and PWM signals for accurate control.
• 💡 Maximum power point tracking (MPPT) is implemented to optimize energy extraction from the wind turbine under varying wind conditions.

Q & A

What is the basic concept of wind power generation?

Wind power generation converts kinetic energy from wind into electrical energy using wind turbines, a gearbox, a generator, power converters, and transformers to feed the energy into the power grid.

How does the Doubly Fed Induction Generator (DFIG) differ from conventional induction machines in wind systems?

The DFIG allows power injection into the grid over a wide range of wind speeds, operating at both sub-synchronous and super-synchronous speeds. Unlike conventional machines, the DFIG's rotor can either absorb or deliver power, making it suitable for variable wind conditions.

What are the three modes of operation for a DFIG wind turbine?

The three modes of operation are: sub-synchronous mode (rotor speed less than synchronous speed), synchronous mode (rotor speed equal to synchronous speed), and super-synchronous mode (rotor speed greater than synchronous speed).

What role does the rotor-side converter (RSC) play in DFIG systems?

The RSC regulates the DFIG to operate in speed and power control modes, managing rotor current through field-oriented control (FOC) and facilitating maximum power point tracking (MPPT) under varying wind conditions.

How does power flow during sub-synchronous operation of the DFIG?

In sub-synchronous operation, the rotor speed is less than synchronous speed, and power is drawn from the grid via the rotor-side converter to the rotor, enabling power injection into the grid through the stator.

What is the function of the grid-side converter (GSC) in a DFIG wind system?

The GSC maintains the DC link voltage by controlling the flow of current between the DC link and the grid. It ensures smooth power transmission and reactive power management in coordination with the RSC.

What happens during synchronous mode of operation in a DFIG system?

During synchronous mode, the rotor speed matches the synchronous speed, meaning no power is injected into or drawn from the rotor. All power is transferred to the grid through the stator.

What is the significance of Maximum Power Point Tracking (MPPT) in wind power generation?

MPPT optimizes the rotor speed at different wind velocities to ensure maximum energy capture from the wind turbine. In DFIG systems, the RSC regulates rotor current to achieve MPPT.

How is the synchronization between the stator and grid achieved in a DFIG setup?

Synchronization is achieved by adjusting the stator voltage and phase angle to match the grid's voltage and phase using rotor-side converter control. Once aligned, the stator can connect to the grid.

What hardware components are used in the DFIG wind turbine test bed demonstration?

The DFIG test bed consists of a wind emulator, a slip ring induction machine, a DC motor, and back-to-back voltage source converters (RSC and GSC), controlled using an FPGA-based controller.

Outlines

00:00

🌬️ Introduction to Wind Power Generation

This paragraph introduces wind power generation as part of a course on smart grid technologies. It briefly describes how kinetic energy from wind is converted into electrical energy through a series of components: wind turbines, gearboxes, generators, power converters, and transformers. The paragraph highlights the aerodynamic modeling of wind turbines and recent advancements in wind generator technology, emphasizing the transition from fixed-type to partially and fully variable generators. It also explains the significance of the doubly fed induction generator (DFIG) system, particularly its cost-effectiveness and adaptability to different wind speeds.

05:01

⚡ Power Flow in a DFIG Wind System

This section delves into the mechanics of the DFIG wind system and its ability to manage power flow in two directions. It explains how the DFIG’s stator is connected to the grid at a fixed voltage and frequency, while the rotor operates at varying speeds, depending on the wind. The DFIG system can inject power into the grid across a range of wind speeds, making it versatile. The rotor draws power from the grid during sub-synchronous operation and contributes excess power during super-synchronous operation. The section concludes by outlining the three modes of operation: sub-synchronous, synchronous, and super-synchronous.

10:02

🔧 Hardware Setup and Components

This paragraph describes the hardware components involved in the wind turbine and DFIG setup. The system includes a wind emulator, a DFIG, and back-to-back voltage source converters. A slip ring induction machine is used in conjunction with a DC motor, which simulates wind characteristics. A buck converter helps mimic wind turbine behavior, and the control strategy for the converter is explained. The DC motor's output is regulated to simulate various wind speeds and emulate real-time wind conditions for the laboratory demonstration of the system.

15:04

🖥️ FPGA Controller and Synchronization Process

This section focuses on the control of the DFIG through a field-programmable gate array (FPGA) controller, which regulates various voltages, currents, and pulses. It details how synchronization between the grid and the DFIG’s stator is achieved using rotor-side control. The RSC (Rotor Side Converter) operates in speed power control mode, and the rotor current is regulated through a field-oriented control (FOC) method. The paragraph also explains the DC link voltage management, the role of the grid-side converter (GSC), and the maximum power point tracking (MPPT) for efficient energy conversion.

20:06

🔄 Synchronization and Speed Control Modes

This paragraph explains the process of entering speed control mode after synchronization is complete. The DFIG operates in three modes: sub-synchronous, synchronous, and super-synchronous. In the sub-synchronous mode, the rotor receives power from the grid. During synchronous mode, the rotor speed matches the grid frequency, and no additional power is drawn. In the super-synchronous mode, both the rotor and stator deliver power to the grid. The paragraph concludes by demonstrating how speed variations are controlled to simulate different wind conditions and operating modes.

Keywords

💡Wind Power Generation

Wind power generation refers to the process of converting kinetic energy from the wind into electrical energy using wind turbines. This is the primary focus of the video, which discusses the mechanics of harnessing wind energy and feeding it into the power grid through various components like generators, converters, and transformers.

💡Doubly Fed Induction Generator (DFIG)

A DFIG is a type of wind power generator capable of feeding power into the grid from both the rotor and the stator. The video highlights how DFIG is preferred due to its ability to operate efficiently at variable wind speeds, making it a cost-effective solution for wind power generation. The DFIG can operate in sub-synchronous, synchronous, and super-synchronous modes.

💡Power Coefficient (Cp)

The power coefficient is a key factor in determining the efficiency of a wind turbine. It represents how much of the wind's kinetic energy is converted into usable electrical energy. In the video, it is explained that Cp is dependent on factors such as the pitch angle and tip speed ratio, influencing how much power the wind turbine can generate.

💡Rotor Side Converter (RSC)

The Rotor Side Converter is a component in the DFIG system that controls the rotor's current and voltage, helping regulate the power fed to the grid. In the video, it is explained how the RSC adjusts the rotor's speed and aligns the phase and voltage of the stator with the grid for synchronization, ensuring stable operation in different wind speed conditions.

💡Grid Side Converter (GSC)

The Grid Side Converter works in conjunction with the RSC to control the DC link voltage and manage the flow of power between the rotor and the grid. It ensures that the DC link voltage is kept stable, allowing smooth power transmission. The video explains that the GSC plays a critical role in maintaining the power quality and enabling reactive power injection to follow grid norms.

💡Synchronous Speed

Synchronous speed refers to the rotational speed at which the rotor of an induction generator aligns with the frequency of the power grid. The video discusses how DFIG can operate in sub-synchronous, synchronous, and super-synchronous modes, and explains that during synchronous speed operation, the rotor and grid frequencies are equal, and power is transmitted solely through the stator.

💡Sub-Synchronous Mode

In sub-synchronous mode, the rotor speed of the generator is lower than the synchronous speed. The video explains that during this mode, the rotor draws power from the grid to maintain grid frequency, and power is injected into the grid via the stator. This mode typically occurs when wind speeds are lower.

💡Super-Synchronous Mode

Super-synchronous mode occurs when the rotor speed exceeds the synchronous speed. In this mode, both the rotor and the stator feed power into the grid. The video illustrates how excess power from the rotor is directed to the grid, making the system capable of handling high wind speeds efficiently.

💡Maximum Power Point Tracking (MPPT)

MPPT is a control algorithm used in wind power systems to ensure that the wind turbine operates at its optimal power output for varying wind speeds. The video explains that the DFIG uses MPPT to adjust rotor speed and maximize energy capture, utilizing a method called 'perturb and observe' to track the maximum power point.

💡Synchronization

Synchronization in the context of the video refers to the process of matching the voltage, frequency, and phase angle of the DFIG stator with the power grid. This step is crucial for ensuring that the power generated by the wind turbine can be smoothly fed into the grid. The video details how synchronization is achieved by controlling the RSC and monitoring the voltage across the stator and grid.

Highlights

Introduction to wind power generation using wind turbines, converting kinetic energy to electrical energy.

Overview of the aerodynamic modeling equations for assessing wind turbine performance based on varying wind speed.

Power generated by a wind turbine is a function of the power coefficient and wind speed.

Transition from fixed-type wind generators to partially variable and completely variable types for improved efficiency.

The doubly fed induction generator (DFIG) system allows bidirectional power flow between the grid and rotor.

DFIG operates effectively with varied wind speeds by allowing both sub-synchronous and super-synchronous operation modes.

During sub-synchronous operation, the rotor speed is less than synchronous speed, and power is drawn from the grid.

In super-synchronous mode, excess rotor power is fed back to the grid, allowing energy injection at higher wind speeds.

The DFIG system can function in three modes: sub-synchronous, synchronous, and super-synchronous, by controlling the rotor-side and grid-side converters.

Detailed explanation of hardware setup for wind turbine grid-connected operation, including wind emulator and voltage converters.

DFIG hardware setup consists of a slip ring induction machine, DC motor as a prime mover, and back-to-back voltage source converters.

A DC motor emulates wind characteristics through a buck converter, with control via armature voltage.

The FPGA-based controller manages DFIG’s stator and rotor current to achieve synchronization with the grid.

Maximum Power Point Tracking (MPPT) implemented using perturb and observe method to optimize wind energy capture.

In synchronous mode, the DFIG rotor operates at synchronous speed, with no power exchange through the rotor.

Transcripts

foreign

[Music]

dear student friends today we are going

to discuss on

demonstration of wind power generation

of the course titled smart grid Basics

to Advanced Technologies

now we are going to discuss on a test

bed for the demonstration of

wind power generation

and as you could see this is the brief

introduction to wind power generation

ideally we capture the kinetic energy

through wind turbines and through

gearbox to the generator and through

power converter to the Transformer and

hence the energy is being fed to the

power grid a typical wind power

generation

convert

kinetic energy of the Wind

to the useful electrical energy

the aerodynamic modeling equations

of the wind turbine

helps to access

the performance of the wind turbine

with respect to the varying wind speed

the power generated from the wind

turbine

is a function

of the power coefficient

and the wind speed

with the recent development in the

semiconductor technology

in the field of wind energy

the less productive fixed type wind

generators

are being replaced

by The partially variable and completely

variable types

among the variable type of generators

the dfig wind system which is one of the

partial variable type

is known for its cost effectiveness

due to the scaled down in the converter

size

the power converters

are rated to handle

complete range of wind speed variations

now focusing on doubly fed induction

generator

so called as dfig wpg the schematic

representation of the dfig wind system

along with the power flow is shown in

this light

is the name suggest

the doubly fed induction generator

is capable of feeding or observing

power in two directions

the stator part is directly exposed to

the grid

which works at fixed voltage

and frequency

henceforth

it is mandatory

that the stator of the dfig

is compelled to operate

as per the grid norms

however

this is only possible

if the rotor operates

at synchronous speed

in a practical scenario

the speed of the generator

keeps on wearing from the sub

synchronous speed

say in the morning hours

when the wind speed is low

to the super synchronous speed in night

hours

when wind speed is extensively High

thus

with the conventional induction machine

it is not possible

to inject power

from the wind system to the grid

with the dfig setup

it is possible to inject power

at varied wind speed

into the grid

via stator

over a speed range of plus or minus 30

percent

during the sub synchronous mode of

operation

since the wind speed is less

the positive slip power is drawn from

the grid

via

rotor side converter

grid side converter

combination to the rotor

such that

the prescribed power at the grid

frequency could be injected from the

stator end

by neglecting the losses of the back to

back converters

where PG equal to p r

we can say that

the power at PCC is equal to the

addition of the power generated by the

wind turbine that is the stator power at

the rotor power

here P equal to P S Plus p g that is the

summation of p s and p g

during the sub synchronous mode of

operation

rotor speed is less than synchronous

speed

and thus the slip is positive

similarly during the supersynchronous

operation

the Excess power from the rotor

in terms of negative slip

power flow out from the rotor via RSC

and GSC

combination thereby helping to follow

the grid Norms as per the nominal values

whereas during the synchronous mode of

operation

there is no power injected or observed

from the rotor and the entire power flow

from the wind system is transferred to

the green

via stator itself in summary

by controlling the RSC and GSC

the dfig wind system can be made to

function

in all the three modes of operation

now focusing on the hardware

demonstration

of the setup of wind turbine

grid connected operation of the dfig

setup

now before going into the demonstration

let us have a look at the overall

Hardware connections

dfig hardware setup

consists of three units mainly

the first one is a wind emulator

dfig

and back to back

voltage source converter

the laboratory setup of dfig is

basically a slip ring induction machine

coupled with DC motor

this DC motor

of rating 2.5 kilowatt

220 volt 10 ampere

which behaves similar to prime mover and

is controlled by Chopper control

providing different wind characteristics

for obtaining the wind emulator

the wind characteristics

along with the wind turbine x n is

mimicked with the help of a buck

converter

the DC motor output is controlled via

Armature voltage control for which the

semicron igbt stack is being used

an inductor and a capacitor is used to

form the buck converter

the control strategy for buck converter

is as shown in the schematic diagram

now the dfig control

so called wind emulator

it can be noticed that

the wind power

which is half of rho a c p v Cube

in the control scheme is calculated by

taking input wind velocity and pitch

angle

here the CP is the power coefficient

which is dependent on the pitch angle

and tip speed ratio

further the wind power is divided with

the measured speed of the rotor to

generate the reference talk

the motor reference current is obtained

by multiplying the torque reference with

the motor constant of value

K which is equal to

4.16 in our case

the current reference is then compared

with the actual current of the DC motor

the compared result is sent to the pi

controller thereby obtaining the

switching pulses

now the induction generator of 2.2

kilowatt

rated and is operated through the field

programmable

gate array fpga based controller

vivect fpga controller a firmware

version wcu10081e

is used which is capable of sensing

eight voltages and eight current signals

along with eight pwm pulses

while the stator of the slip ring

induction motor

is connected to the power amplifier via

a switch

the switch is initially open

and is further closed when the stator

voltage and phase angle is synchronized

with the voltage and phase of the grid

and phase angle using the rotor side

converter

after synchronization

RSC regulates

d f i g to operate

in the speed power control mode

rotor of slip ring induction motor is

connected to the RSC which is controlled

in the fpga platform

now if you look into the dfig control

through rotor site

field oriented control FOC

established on the vector control is

enlist for D and Q axis control

of rotor current

the maximum PowerPoint tracking mppt is

implemented using perturb and observe p

and O method by estimating

mppt reference rotor speed

at particular wind velocity regulating

the Q axis

of the rotor current IQ RSC

now the D X is part of the rotor current

is governed for managing the stator

power factor this is done by introducing

reactive power for smooth variation

further

the reference voltage is converted

to the ABC frame to generate the pwm

signals which is fed to the RSC switches

the RSC is connected to GSC via a DC

link and the job of the GSC is to

maintain the DC link voltage

now looking into grid side control the

generated DC link voltage when compared

with the measured voltage of DC link

generate error that is processed through

Pi controller to obtain d-axis reference

current

the measured GSC current d-axis

component tracks the reference value

with the pi controller to obtain the

reference DXs voltage

while the pi controller dealing with the

Q axis component of GSC current is

assigned to regulate reactive power

injection

now the software which is available

through WebEx suit for fpga controller

that run on HDL coder

in this platform we provide the

governing variables value

first we connect the WebEx via a lan

cable

to the PC

and connect the supply voltages

the supply voltage we give by power

amplifier

of rating 15 kilovolt ampere and 50

hertz

the three phase voltage is set in the

amplifier

140 volt to get line to line voltage of

240 volts

the grid voltage is reflected

in the software due to presence of

voltage sensor at that point

the main and the rotor branch circuit

breaker

is switched on and the DC link is

charged initially to 340 volts

then we enable

phase locked Loop and check the

reference Theta with the phase a voltage

once the DC link is charged

we enable the GSC control

to maintain the desired DC link voltage

which is said to say

30 volt greater than DC link voltage

that is close to

380 volts

we see that GSC track the DC reference

voltage and measured DC link voltage

is red as 385 volts

now the next step

is to enable

DC motor control to run the DC motor

to provide wind characteristic in the

rotation

here

we vary the duty of the chopper

gradually to make the motor run at more

than

900 RPM

we are wearing the duty and notice that

speed is keep on increasing

we can check the rotation here in the

speed panel

we see the DC motor is driving the

induction machine

next we provide

the p i value of the rotor side control

and enable the control Loop

the RSC first

is used to build up voltage in the

stator

site and then match the phase difference

of the grid

to the stator

till they align for the synchronization

purpose

now we will increase the reference value

to match the stator voltage magnitude

with the grid voltage using the D axis

control of the rotor

in this process

we also observe that the rotor current

is also increased

as it takes current from the grid

to build the stator voltage as from the

relation

the stator power is 1 by slip times the

rotor power I repeat in this process we

also observe that the rotor current is

also increased

as it takes current from the grid to

build the stator voltage is from the

relation the stator power is one by slip

times the rotor power

the slip is varied plus or minus 30

percent

so small current injected to rotor side

results in a larger voltage across the

stator

then we vary the Q axis of the RSC to

vary the Theta

we change the reference till Theta is

matched

if we see the grid and stator voltage

we see the waveform almost overlap with

one another

after voltage get matched in the

software then we check the

contactor of the grid side and Status

side and ensure that the voltage across

the contactor in multimeter is less than

20 volt

here we are getting a value of less than

10 volt across all three phases

by ensuring voltage is less then the

contactor connecting the stator

and the grid connection is closed and

then the synchronization is done by

enabling sync done in the software

simultaneously

now the control of RSC is changed from

synchronization operation to power speed

control mode

here we see that the three phase rotor

power is sent

now we enter the speed control mode and

Vary the wind speed to vary the rotor

speed

here we demonstrate the dfig in three

different operating modes

number one sub synchronous mode

to synchronous mode and three

supersynchronous mode now in case of the

sub synchronous mode the rotor angular

frequency is lower than the synchronous

angular frequency

where

Omega R is less than Omega s

we consider Omega s which is close to

1000 RPM and the slip is greater than

zero

the total power to the grid is 1 minus

slip times P stator

the stator delivers power to the grid

while the rotor receives power from the

grid

next we slowly increase the speed and

bring it in the synchronous mode

the rotor angular frequency

is equal to the synchronous angular

frequency where Omega r equal to Omega s

and the slip which is equal to zero

DC current flows into the rotor binding

the total power to grid is p which is

stator power only the stator delivers

power to the grid

if we further increase the speed of the

d f i g works in the super synchronous

mode

the rotor angular frequency is higher

than the synchronous angular frequency

that is Omega R is greater than Omega s

and hence the slips false Which is less

than zero

the total power

to the grid is p which is one plus slip

time P stator

now both the stator and the rotor

deliver power to the grid

with this we have today

understood how

a d f i IG wind turbine operates

and thank you for your attention

[Music]