Unified theorys active and reactive powers

Energy2green Wind And Solar Power System

Wind Energy DIY Guide

Get Instant Access

Fundamental positive-sequence complex power supplied by the wind generator showed in fig. 1 is expressed as:

S+ = 3 Va+ ■ 1A + = 9VA +• (Ye + % • Y/) = P+ + Q+ (15)

Positive-sequence active power (P+) is the real part of the above quantity and it characterizes the direct torque applied to the axis of the wind-generator. This quantity has two components, due to the active loads (Pa+ ) and caused by the unbalances (Pu+ ):

P+ = 3 Va+ • 1Aa+ = 9VA +• (Ge +Su • Yi • cos (a+ - a- + a) = Pa++ Pu+

Pu+= 3 Va+ • 1Aau + = 9 Su ■ • cos (a+ -a+a) •

Pa+ is the positive-sequence active power supplied by the wind-generator under positive-sequence balanced voltages; thus, it may be defined as the positive-sequence active power due to the load consumptions. This quantity measures the active power which is transformed under the best efficiency and power quality conditions. Pu+ represents the increasing of the positive-sequence active power produced by the voltage and load unbalances. Last quantity identifies the poor power quality in the power system, since it occurs when there are voltage unbalances, and it may have the same or different sign that Pa+ , so it increases or decreases the total positive-sequence active power (P+ ). Positive-sequence reactive power ( Q+ ) is the module of the imaginary part of the positive-sequence complex power. Expressed in complex notation, this quantity has the following formulation:

Q+ = 3 VA+ • ^Ar + = j 9VA+ ■ (Ye ' sin ae + Su ' Yi ' sin(a+ - a- + ai )) = (17)

= j 9VA+ • (±Be +Su • Yt • sin(a+ -a-+ai)) = Qr + + Qu+

Positive-sequence reactive power characterizes the main magnetic field of the windgenerator and it holds two components, due to the reactive loads (Qr + ) and caused by the unbalances (Qu+ ):

Qr + = 3 VA+ • lArr + = j 9 Ye • sin ae • VA+ = ±j 9 Be VA+

Qu+ = 3 VA+ ' hru+ = j 9 Su ■ Yi • sin(a+ -a-+ai ) • VA+

Qr + is the positive-sequence reactive power supplied by the wind-generator under positive-sequence balanced voltages. This quantity determinates the reactive power established under the best efficiency and power quality conditions. Qu+ defines the increasing of the positive-sequence active power produced by the voltage and load unbalances. This quantity identifies the poor power quality in the power system, since it occurs when there are voltage unbalances, and it may have the same or different character (inductive or capacitive) that Qr +, and thus it can increase or decrease the positive-sequence reactive power , Q+ .

Was this article helpful?

0 0
Renewable Energy 101

Renewable Energy 101

Renewable energy is energy that is generated from sunlight, rain, tides, geothermal heat and wind. These sources are naturally and constantly replenished, which is why they are deemed as renewable. The usage of renewable energy sources is very important when considering the sustainability of the existing energy usage of the world. While there is currently an abundance of non-renewable energy sources, such as nuclear fuels, these energy sources are depleting. In addition to being a non-renewable supply, the non-renewable energy sources release emissions into the air, which has an adverse effect on the environment.

Get My Free Ebook


Post a comment