A Method of Primary Frequency and Inertia Control of Photo-voltaic Station

Consumption of traditional fossil fuel is becoming a very serious problem, so countries all over the world have begun to pay more and more attention to clean renewable energy generation such as photovoltaic generation and the in-grid technologies. Most new types of generation need to be connected to power grid with inverters. The inverters have no inherent rotational inertia and its primary frequency modulation characteristics are different from that of electric machine, which will bring harmful impact to power grid. Firstly, the primary frequency modulation characteristic of synchronous machine is analyzed, and a new frequency modulation strategy considering dead zone and equivalent offset of rotor speed is proposed, advantages and feasibility of the strategy is verified by simulation example of photovoltaic station. Secondly, characteristics of mechanical inertia of synchronous machine are analyzed, and a feedback control method not relying on external frequency signals but on measured power deviation is proposed and verified by simulation as above. Finally, a combined control strategy considering equivalent mechanical inertia and primary frequency modulation is proposed, which is also verified by simulation case.