The rapid increase in renewable energy integration brings with it a series of uncertainty to the transmission and distribution systems. In general

large-scale wind and solar power integration always cause short-term mismatch between generation and load demand because of their intermittent nature. The traditional way of dealing with this problem is to increase the spinning reserve

which is quite costly. In recent years

it has been proposed that part of the load can be controlled dynamically for frequency regulation with little impact on customers' living comfort. This paper proposes a hybrid dynamic demand control (DDC) strategy for the primary and secondary frequency regulation. In particular

the loads can not only arrest the sudden frequency drop

but also bring the frequency closer to the nominal value. With the proposed control strategy

the demand side can provide a fast and smooth frequency regulation service

thereby replacing some generation reserve to achieve a lower expense.