Method and system for controlling a renewable energy plant

A method for controlling power flow between a renewable energy plant and an electric power grid, the renewable energy plant having an intermittent energy source, the method comprising:

• using a renewable energy plant control system, measuring power output from the renewable energy plant and determining a first difference signal between the measured power output from the renewable energy plant and a power reference;
• measuring frequency deviation of the power output from the renewable energy plant and determining a second difference signal between the measured frequency deviation and a frequency deviation reference;
• generating a first error signal by limiting a sum of the first and second difference signals between predetermined minimum and maximum power error limits;
• modelling power output from the intermittent energy source and determining a second error signal between the modelled power output from the intermittent energy source and a control signal applied to the intermittent energy source to control the power output therefrom;
• and,
• generating the control signal by applying the first and second error signals to a proportional-integral loop.