Impact of smart transformer voltage and frequency support in a high renewable penetration system

Increasing penetration of power electronics interfaced generation decreases the stability of the system, due to the absence of the rotational inertia in their operation. Emulation of the inertia using converter controls in combination with storages can address this issue. However, this method relies on the use of large quantities of storage to compensate power during a transient power unbalance. Instead of increasing the supply, the smart transformer (ST), with a fast response, offers the possibility to dynamically regulate the demand. This paper investigates the use of an ST to dynamically control reactive power and demand to support voltage and frequency respectively in the grid. The demand is controlled dynamically to emulate inertia. From an analysis based on a 250 kVA, 10kV/400V LV distribution network, it is shown that a demand variation in the range of 6-10% can be achieved. These results are extended to a case study based on the entire all-Island Irish Transmission system which shows that widespread use of STs with these controls could potentially facilitate a 10% increase in wind penetration without the inclusion of any other storage.