Reactive power control for operating a wind farm

1. A method of reactive power regulation in a wind farm having a plurality of wind turbines, comprising:

obtaining a reactive power setpoint (Sp_Q);

measuring a reactive power output of the wind farm (Av_Q);

calculating an error (ε_Q) between the reactive power setpoint and the measured reactive power output;

using the error (ε_Q) as input to a PID controller to generate a relative reactive power command (Sp_% Qmax);

sending the relative reactive power command (Sp_% Qmax) to each of the plurality of wind turbines; and

applying the relative reactive power command (Sp_% Qmax) as a percentage to an instantaneous maximum reactive power capacity (Qwt_max) in performing power regulation for each of the wind turbines.

2. The method of claim 1 further comprising the steps of:

prioritizing the reactive power over the real power production (RPP) if the relative reactive power command (Sp_% Qmax) has reached a maximum allowed value;

using the error (ε_Q) to generate a relative real power limit command (% Pwt_rated) if the reactive power production is prioritized over the real power production;

sending the relative real power limit command (% Pwt_rated) to each of the plurality of wind turbines; and

applying the relative real power limit command (% Pwt_rated) in each of the plurality of wind turbines as a percentage of a rated real power to obtain a real power production limit.

3. A method according to claim 2 , wherein the relative reactive power command (Sp_% Qmax) and the relative real power limit command (% Pwt_rated) are calculated by using an economic profit optimization algorithm.

4. A method according to claim 1 , wherein the relative reactive power command (Sp_% Qmax) is calculated by using an economic profit optimization algorithm.

5. A method of reactive power reserve regulation in a wind farm having a plurality of wind turbines, comprising:

prioritizing a reactive power reserve over the real power production (RRP);

obtaining a reactive power reserve setpoint (Sp_Qres);

calculating a reactive power reserve of the wind farm (Av_Qres);

calculating an error (ε_Qres) between the reactive power reserve setpoint and the calculated reactive power reserve of the wind farm;

using the error (ε_Qres) to generate a relative real power limit command (% Pwt_rated);

sending the relative real power command (% Pwt_rated) to each of the wind turbines; and

applying the relative real power command (% Pwt_rated) in each wind turbine as a percentage of the rated real power to obtain a real power production limit.

6. A method according to claim 5 , wherein relative real power limit command (% Pwt_rated) is calculated by using an economic profit optimization algorithm.

7. A method for generating a reactive power setpoint for a power control unit of a wind turbine, comprising:

calculating a reactive power capacity of an electrical system of the wind turbine (Qwt_max_ele_sys) and limiting the calculated reactive power capacity by applying a voltage surveillance value (Gv) that takes into account grid conditions to obtain an instantaneous maximum reactive power capacity (Qwt_max);

receiving a relative reactive power command (Sp_% Qmax); and

applying the relative reactive power command (Sp_% Qmax) to the obtained instantaneous maximum reactive power capacity (Qwt_max) to generate a reactive power setpoint (Sp_Qwt) for the power control unit.

8. A method of power regulation in a wind farm having a plurality of wind turbines, comprising:

generating a reactive power command and a real power command by using an economic profit optimization algorithm; and

sending the generated reactive power command and the real power command to the plurality of wind turbines.