Wind Utility FACTS

A STATIC COMPENSATION METHOD BASED SCHEME

FOR IMPROVEMENT OF POWER QUALITY IN WIND

GENERATION

Under the Guidance, Project Members V.Satyanarayana,M.Tech V.ANJITH

KUMAR(08MF1A0215)K.D PAVAN KUMAR(08MF1A0223)

V.SRINIVASA RAO(08MF1A0252)D.BRIJESH(08MF1A0220)

Introduction

• Wind is a renewable Green Energy source

Load

kinetic Energy

Mechanical Energy

Electrical Energy

Introduction

• Wind is also a clean Abundant Source

• No Emissions, No Pollutions

sulfur dioxide

particulates

carbon dioxide

Introduction• One of the main problems in wind energy generation is the connection to the grid.

Injection of wind power into the grid affects the power quality resulting in poor performance of the system. The wind energy system faces frequently fluctuating voltage due to the nature of wind and introduction of harmonics into the system. Injection of the wind power into an electric grid affects the power quality. The performance of the wind turbine and thereby power quality are determined on the basis of measurements and the norms followed according to the guideline specified in International Electro-technical Commission standard, IEC-61400. The influence of the wind turbine in the grid system concerning the power quality measurements are-the active power, reactive power, variation of voltage, flicker, harmonics, and electrical behavior of switching operation and these are measured according to national/international guidelines. The paper study demonstrates the power quality problem due to installation of wind turbine with the grid.

Introduction

0

2000

4000

6000

8000

10000

12000

14000

16000

18000

20000

Germany USA Denmark CANADA

2004 (MW)2005 (MW)

Total installed wind power MW-capacity（ data from World Wind Energy Association)

Introduction

• Wind Energy Conversion System (WECS) Using Large Squirrel Cage/Slip ring Induction Generators– Stand alone-Village Electricity– Electric Grid Connected WECS

• Distributed/Dispersed/Farm Renewable Wind Energy Schemes– Located closer to Load Centers– Low Reliability, Utilization, Security

Motivations

• Energy crisis– Shortage of conventional fossil fuel based energy

– Escalating/rising cost of fossil fuels

• Environmental/Pollution/GHG Issues – Greenhouse gas emission /Carbon Print

– Acid Rain/Smog/VOC-Micro-Particulates

– Water/Air/Soil Pollution &Health Hazards

Motivations

• Large wind farm utilization is also emerging (50MW-250 MW) Sized Using Super Wind driven Turbines 1.6, 3.6, 5 MW Sizes

• Many new interface Regulations/Standards/PQ Requirements regarding full integration of large distributed/dispersed Wind Farms into Utility Grid.

Motivations

• Challenges for Utility Grid–Wind Integration.– Stochastically-Highly Variable wind power injected into the Utility

Grid.

– Increased Wind MW-Power penetration Level.

– Low SCR-Weak Distribution/Sub Transmission/Transmission Networks

- Mostly of a Radial Configuration

- Large R/X ratio distribution Feeder with high Power Losses (4-10 %), Voltage Regulation Problems/Power Quality/Interference Issues.

– Required Reactive Power Compensation & Increased Burden brought by the induction generator

WECS

Sample Distribution Study System

L.L.1 L.L.2

L.L.3N.L.L

I.M.

T1T3T2

Infinite Bus

WECS-Decoupled Interface Scheme

Cself

WindTurbine

I.G.Lf

Cf

UncontrolledRectifier

PWMInverter

To Grid

DC LinkInterface

System Description-wind turbine

• Wind turbine model based on the steady-state power characteristics of the turbine

– S -- the Total BladeArea swept by the rotor blades (m^2)

– v -- the wind velocity (m/s)– ρ--air density (kg/v^3)

31

2m pP C S V

System Description

3

21 3 4 6( , ) i

c

pi

CC C C C e C

tip speed ratio λ is the quotient between the

tangential speed of the rotor blade tips

and the undisturbed wind

velocity

3

1 1 0.035

0.08 1i

C1=0.5176, C2=116,

C3=0.4, C4=5, C5=21 and C6=0.0068

System Description – Wind speed

• The dynamic wind speed model consists of four basic components:– Mean wind speed-14 m/s– Wind speed ramp with a slope of ±5.6– Wind gust

• Ag: the amplitude of the gust• Tsg: the starting time of the gust • Teg: the end time of the gust• Dg = Teg - Tsg

– Turbulence components: a random Gaussian series

[1 cos(2 ( / / ))]g g sg gv A t D T D

Wind Speed Dynamic Model

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.80

2

4

6

8

10

12

14

16

18

Time (Second)

Win

d S

peed

(m

/s)

The eventual windspeed applied to the wind turbine is the summation

of all four key components.

MPFC-FACTS Scheme 1

• Complementary PWM pulses to ensure dynamic topology change between switched capacitor and tuned arm power filter

• Two IGBT solid state switches control the operation of the MPFC via a six-pulse diode bridge

Tri-loop Error Driven Controller

VoltageStabilization

loop

Current Dynamic Error Tracking loop

Current HarmonicTracking Loop

ModulationIndex

DVR-FACTS Scheme 2

• A combination of series capacitor and shunt capacitor compensation

• Flexible structure modulated by a Tri-loop Error Driven Controller

If S1 is high and S2 is low, both the series and

shunt capacitors are connected into the circuit, while the

resistor and inductor will be fully shorted

If S1 is low and S2 is high, the series capacitor will be removed from the system, the resistor and inductor will be connected to the

shunt capacitors as a tuned arm filter

HPFC-FACTS Scheme 3

• Use of a 6-pulse VSC based APF to have faster controllability and enhanced dynamic performance

• Combination of tuned passive power filter and active power filter to reduce cost

PWM converter

DC Capacitor to provide the

energizing voltage

Passive Filter tuned

near 3rd harmonicfrequency

Coupling capacitor

Coupling transformer

Novel Scheme-3 Multi-loop Error Driven Controller

Novel Decoupled Multi-loop Error Driven Controller

• Using decoupled direct and quad. (d , q) voltage components

• Using The Phase Locked Loop (PLL) to get the required synchronizing signal- phase angle of the synthesized VSC-Three Phase AC output voltages with Utility-Bus

• Using Proportional plus Integral (PI) controller to regulate any tracked errors

• Using Pulse Width Modulation-PWM with a variable modulation index -m

Novel Decoupled Multi-loop Error Driven Controller

• Outer-Voltage Regulator: Tri-loop Dynamic Error-Driven controller– The voltage stabilization loop

– The current dynamic error tracking loop

– The dynamic power tracking loop

• Inner-Voltage Regulator: Mainly to control the DC-Side capacitor charging and discharging voltage to ensure almost a near constant DC capacitor voltage

Controller Tuning

• Control Parameter: Selection/optimization• Using a guided Off-Line Trial-and-Error Method based

on successive digital simulations – Minimize the objective function-Jo

– Find optimal Gains: kp, ki and individual loop weightings (γ) to yield a near minimum Jo under different set-selections of the controller parameters

2

1

( )N

o tk

J e k

Where settling time count N settling

sample

T

T

00.5

11.5

2

05

1015

0

0.2

0.4

0.6

0.8

1

Kp

A Sample of J0-Ki-Kp 3-phase-portrait for Controller Parameter Searching

Ki

Jo

Digital Simulation

• Digital Study System Validation is done by using Matlab/Simulink/Sim-Power Software Environment under a sequence of excursions:– Load switching/Excusrions

• At t = 0.2 second, the induction motor was removed from bus 5 for a duration of 0.1 seconds;

• At t = 0.4 second, linear load was removed from bus 4 for a duration of 0.1 seconds;

• At t = 0.5 second, the AC distribution system recovered to its initial state.

– Wind-Speed Gusting changes modeled by dynamic wind speed-Software model

Digital Simulation

• Digital Simulation Environment: MATLAB /Simulink/Sim-Power• Using the discrete simulation mode with a

sample time of 0.1 milliseconds• The digital simulations were carried out

without and with the novel FACTS-based devices located at Bus 5 for 0.8 seconds

System Dynamic Responses at Bus 2 without and with MPFC

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.80

0.51

1.5

Per

uni

t

Voltage (L-L rms)

with compensation

without compensation

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.80135

Per

uni

t

Current (rms)

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8-1012

Per

uni

t

Real Power

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8-2-101

Per

uni

t

Reactive Power

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.80

0.511.1

Time (Second)

Power Factor

System Dynamic Responses at Bus 3 without and with MPFC

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.80

0.51

1.52

Per

uni

t

Voltage (L-L rms)

with compensation

without compensation

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.80

0.51

1.5

Per

uin

t

Current (rms)

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.80

0.51

Per

uni

t

Real Power

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8-0.5

00.5

1

Per

uni

t

Reactive Power

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.80

0.51

Time (Second)

Power Factor

System Dynamic Responses at Bus 5 without and with MPFC

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.80

0.51

1.5

Per

uni

t

Voltage (L-L rms)

with compensation

without compensation

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.80

0.51

1.5

Per

uni

t

Current (rms)

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.80

0.51

Per

uni

t

Real Power

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8-101

Per

uni

t

Reactive Power

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.80

0.51

Time (Second)

Power Factor

The frequency variation at the WECS interface without and with MPFC

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.856

57

58

59

60

61

62

Time (Second)

Fre

quen

cy (

Hz)

with compensation

without compensation

System Dynamic Responses at Bus 2 without and with DVR

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.80

0.51

1.5P

er u

nit

Voltage (L-L rms)

with compensation

without compensation

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8013

Per

uni

t

Current (rms)

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8-1012

Per

uni

t

Real Power

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8-2-101

Per

uni

t

Reactive Power

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.80

0.51

Time (Second)

Power Factor

System Dynamic Responses at Bus 3 without and with DVR

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.80

0.51

1.5

Per

uni

t

Voltage (L-L rms)

with compensation

without compensation

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.80

0.51

1.5

Per

uni

t

Current (rms)

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.80

0.51

Per

uni

t

Real Power

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8-1012

Per

uni

t

Reactive Power

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.80

0.51

Time (Second)

Power Factor

System Dynamic Responses at Bus 5 without and with DVR

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.80

0.51

1.5P

er u

nit

Voltage (L-L rms)

with compensation

without compensation

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.80

0.51

Per

uni

t

Current (rms)

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.80

0.5

Per

uni

t

Real Power

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8-0.5

00.5

1

Per

uni

t

Reactive Power

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.80

0.51

Time (Second)

Power Factor

The frequency variation at the WECS interface without and with DVR

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.856

57

58

59

60

61

62

Time (Second)

Fre

quen

cy (

Her

z)

with compensation

without compensation

System Dynamic Responses at Bus 2 without and with HPFC

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.80

0.51

1.5

Per

uni

t

Voltage (L-L rms)

with compensation

without compensation

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8013

Per

uni

tCurrent (rms)

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8-1012

Per

uni

t

Real Power

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8-101

Per

uni

t

Reactive Power

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.80

0.51

Time (second)

Power Factor

System Dynamic Responses at Bus 3 without and with HPFC

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.80

0.51

1.5P

er u

nit

Voltage (L-L rms)

with compensation

without compensation

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.80

0.51

Per

uni

t

Current (rms)

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8-0.2

0

0.5

Per

uni

t

Real Power

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8-0.5

0 0.5

Per

uni

t

Reactive Power

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.80

0.51

Time (Second)

Power Factor

System Dynamic Responses at Bus 5 without and with HPFC

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.80

0.51

1.5P

er u

nit

Voltage (L-L rms)

with compensation

without compensation

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.80

0.51

1.5

Per

uni

t

Current (rms)

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.80

0.51

Per

uni

t

Real Power

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8-0.5

00.5

1

Per

uni

t

Reactive Power

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.80

0.51

Time (Second)

Power Factor

The frequency variation at the WECS interface without and with HPFC

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.856

57

58

59

60

61

62

Time (Second)

Fre

quen

cy (

Her

z)

with compensation

without compensation

Comparison of Voltage THD with Different Compensation Scheme

Busnumber

Withoutcompensator

WithMPFC

WithDVR

WithHPFC

1 28.39% 4.90% 11.9% 4.99%

2 32.70% 4.60% 12.2% 4.88%

3 35.95% 4.29% 12.6% 4.69%

4 35.75% 3.51% 12.2% 4.51%

5 35.77% 3.32% 13.1% 3.90%

6 36.04% 3.57% 8.57% 4.57%

Comparison of Steady-state Bus Voltage with Different Compensation Scheme

Busnumber

Withoutcompensator

WithMPFC

WithDVR

WithHPFC

1 0.97 1.02 1.01 1.05

2 0.95 1.00 1.03 1.05

3 0.94 1.00 1.02 1.05

4 0.89 0.99 1.02 1.05

5 0.86 0.99 1.02 1.06

6 0.83 0.96 1.03 1.05

Conclusions

• Three Novel FACTS-based Converter & Control schemes, namely the MPFC, the DVR, and the HPFC, have been Developed and validated for voltage stabilization, power factor correction and power quality improvement in the distribution network with dispersed wind energy integrated.

Recommendation

• The Low-Cost MPFC-Scheme 1 is preferred for low to medium size wind energy integration schemes (from 600 to 5000 kW).

• The DVR-Scheme 2 is good for Strong AC sub-transmission and distribution systems with large X/R ratio

• The HPFC-Scheme 2 Active Power Filter & Capacitor Compensator is most suitable for Larger Wind-Farms with MW-energy penetration level (100 MW or above).

Recommendation

• The schemes validated in this research need to be fully tested in the distribution network with real dispersed wind energy systems.

• This research can be extended to the grid integration of other dispersed renewable energy.

• Other Artificial Intelligence based control strategies can be investigated in future work.

Conclusions

• A Validation Study of a unified sample study system Using the MATLAB/Simulink

• A dynamic wind speed software model was developed to simulate the varying Random/Stochastic and temporal wind variations in the MATLAB/Simulink

• Three Novel FACTS based Stabilization Schemes were validated using digital simulations

• Novel Control strategies using dynamic Multi-Loop Decoupled Controllers were developed & Validated

Publications• [1] A. M. Sharaf and Weihua Wang, ‘A Low-cost Voltage Stabilization and Power Quality

Enhancement Scheme for a Small Renewable Wind Energy Scheme’, 2006 IEEE International Symposium on Industrial Electronics, 2006, p.1949-53, Montreal, Canada

• [2] A. M. Sharaf and Weihua Wang, ‘A Novel Voltage Stabilization Scheme for Standalone Wind Energy Using A Dynamic Sliding Mode Controller’, Proceeding- the 2nd International Green Energy Conference, 2006, Vol. 2, p.205-301, Oshawa, Canada

• [3] A. M. Sharaf, Weihua Wang, and I. H. Altas, ‘Novel STATCOM Controller for Reactive Power Compensation in Distribution Networks with Dispersed Renewable Wind Energy ’, 2007 Canadian Conference on Electrical and Computer Engineering, Vancouver, Canada, April, 2007

• [4] A. M. Sharaf, Weihua Wang, and I. H. Altas, ‘A Novel Modulated Power Filter Compensator for Renewable Dispersed Wind Energy Interface’, the International Conference on Clean Electrical Power, 2007, Capri, Italy, May, 2007

• [5] A. M. Sharaf, Weihua Wang, and I. H. Altas, ‘A Novel Modulated Power Filter Compensator for Distribution Networks with Distributed Wind Energy ’ (Accepted by International Journal of Emerging Electric Power System)