Inertial response

Inertial Response is a property of large synchronous generators, which contain large synchronous rotating masses, and which acts to overcome the immediate imbalance between power supply and demand for electric power systems, typically the electrical grid. Due to the ever existing power imbalance between mechanical power supply and electric power demand the rotational frequency of the rotating masses in all synchronous generators in the grid either speed up (excess power supply) or slow down (excess power demand). This enables the grid operator to rebalance the system in order to stop the speed change, resulting in a relatively small variation in AC frequency ideally within the allowable frequency range of that system. i.e. A 50 Hz system may allow a ±0.5 Hz deviation in the frequency of the AC voltage The grid frequency is the combined result of the detailed motions of all individual synchronous rotors in the grid, which are modeled by a general equation of motion called the Swing Equation.
Simulating power balancing with wind power.
When the grid frequency is too high or too low, active power flow through the high-voltage direct current link will be ramped down or up. In turn, the wind generation will increase or decrease the blade angles to reduce or increase the captured wind power through pitch control.