1 / 27

# Reactive power injection strategies for wind energy regarding its statistical nature - PowerPoint PPT Presentation

Reactive power injection strategies for wind energy regarding its statistical nature . Joaquín Mur M.P. Comech joako@unizar.es mcomech@unizar.es. Wind site resource Turbine power curve Farm power curve Farm electric model Nearby wind farms Limits on reactive power. Reactive Power Policy

I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.

## PowerPoint Slideshow about 'Reactive power injection strategies for wind energy regarding its statistical nature' - Pat_Xavi

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.

- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript

### Reactive power injection strategies for wind energy regarding its statistical nature

Joaquín Mur M.P. Comech

joako@unizar.esmcomech@unizar.es

Wind site resource regarding its statistical nature

Turbine power curve

Farm power curve

Farm electric model

Nearby wind farms

Limits on reactive power

Reactive Power Policy

Constant power factor

Automatic voltage control

Scheduled Reactive control

Reactive power under centralized control

Effect on power losses

Uncertainty Analysis

Conclusions

I. Introduction: presentation layout

II. Wind site resource regarding its statistical nature (Weibull distribution)

Chart for shape parameter = 2

Solid red => wind speed = 5 m/s

Dashed pink=>wind speed = 5,5 m/s

Dark blue => wind speed = 6 m/s

Light blue => wind speed = 6,5 m/s

Dotted green=>wind speed = 7 m/s

Yellow => wind speed = 7,5 m/s

III. Wind turbine regarding its statistical nature (IEC 61400-12-1)

Power curve measured at a pitch regulated turbine (from IEC 61400-12-1)

III. Snapshoot of turbines in a farm regarding its statistical nature

Power curve measured at a pitch regulated turbine (from IEC 61400-12-1)

IV. Wind farm curve regarding its statistical nature (IEC 61400-12-3)

Declared (calculated) wind farm power curve by directional sector (from IEC 61400-12-3, annex C)

IV. Wind farm regarding its statistical nature (4 parameters adjusted curve)

woff

wf is the farm mean efficiency factor(referred to “unperturbated wind” of the site).

w25%

w75%

woff

IV. Farm power distribution regarding its statistical nature

IV. Farm power distribution regarding its statistical nature

Chart for shape factor k = 2

Solid red => wind speed = 5 m/s

Dashed pink=>wind speed = 5,5 m/s

Dark blue => wind speed = 6 m/s

Light blue => wind speed = 6,5 m/s

Dotted green=>wind speed = 7 m/s

Yellow => wind speed = 7,5 m/s

Dashed red => wind speed = 8 m/s

V. Model of the wind farm with regarding its statistical nature several medium voltage circuits

V. Approximated equivalent model of the wind farm regarding its statistical nature

• Averaged model

V. Fourth pole model & parameters of the farm regarding its statistical nature

Nearby wind farms are supposed to be closely correlated regarding its statistical nature  a linear regression can be precise enough

VI. Power of nearby farms

• Pi and Pj are the average power output in park “j” (estimated farm) and “i” (reference farm);

• rijis the experimental correlation coefficient;

• si and sjare the standard deviation of power in farms i and j.

• Qi and Qj must be estimated based on each farm reactive control

VII. Limits on reactive power regarding its statistical nature

• Limits provided by the turbine manufacturer.

• Second edition of IEC 61400-21 will include a section devoted to the reactive power capability and the ability to participate in an automatic voltage control scheme.

• Allowable voltage at the turbines.

• The wind turbine that is electrically farer from PCC will suffer the greatest voltage deviations of the wind farm.

• Voltage at turbines is dependent on UPCC

• Current limit in series elements (lines, transformers, etc) and grid bottlenecks.

• Slow thermal dynamics, grid congestion…

• Usually, some degree of overload is allowed.

VII. Voltage at electrically farer turbine regarding its statistical nature

• Estimation of parameters from power flows:

VII. Loci of allowable power regarding its statistical nature

Centralized control: stabilize voltage, power losses, balance reactive power flows…

Constant power factor regulation

Automatic voltage control

Scheduled reactive control

Current model in Spain, power factor depending on hours

Improvement if weekdays and holidays would be considered

Improvement if target is based on reactive power, not on power factor

VIII. Reactive power policy

Medium hours balance reactive power flows…

12 h/day

(unity power factor)

Valley hours

8 h/day

Peak hours

4 h/day

(Capacitive behaviour)

VIII. Voltage deviation due to scheduled power factor (Spain)

Peak hours

4 h/day

(Capacitive behaviour)

Valley hours

8 h/day

• Simplistic example of realizable reactive power at a wind turbine

• Probability of being able to INJECT capacitive power up to Qwt

Chart for shape parameter = 2

Solid red => wind speed = 5 m/s

Dashed pink=>wind speed = 5,5 m/s

Dark blue => wind speed = 6 m/s

Light blue => wind speed = 6,5 m/s

Dotted green=>wind speed = 7 m/s

Yellow => wind speed = 7,5 m/s

• Probability of being able to ABSORB inductive power up to Qwt

Chart for shape parameter = 2

Solid red => wind speed = 5 m/s

Dashed pink=>wind speed = 5,5 m/s

Dark blue => wind speed = 6 m/s

Light blue => wind speed = 6,5 m/s

Dotted green=>wind speed = 7 m/s

Yellow => wind speed = 7,5 m/s

IX. Effect on power losses example

• Parameters aP, aQ, bP and bQ can be obtained from power flow runs

• An analogue relationship can be established for losses on reactive power

The main source of errors are:

• Adjustment of wind resource to a Weibull distribution.

• The uncertainty of the farm power curve.

• Simplistic model of the power curve with only two or four parameters.

• Approximations done in the model of the grid (for example, considering U0 constant).

• Availability of turbines and network.

Conclusions example

• This work shows a statistical model of wind farms and a methodology for adjusting its parameters. This model has been used to assess the grid impact of a wind farm reactive power during normal operation.

• Several reactive power control strategies are analyzed.

• The uncertainty of the final data due to the approximations made is studied. The accuracy can be increased if non-parametric models of farm power curve and wind resource is employed.