The traditional frequency modulation methods of power grid include

The voltage depends on the reactive power balance in the system. If there is excess reactive power, the voltage will rise, and if there is insufficient reactive power, the voltage will drop. The frequency depends on the balance of active power. Excessive active power will increase the frequency, while insufficient active power will decrease the frequency.

The main methods of frequency regulation in power system are power generation regulation and load management. According to the different adjustment range and ability, frequency modulation can be divided into primary frequency modulation, secondary frequency modulation and tertiary frequency modulation. Primary frequency modulation means that when the power system frequency deviates from the target frequency, the generator set adjusts the active output through the automatic response of the speed control system to maintain the frequency stability of the power system. Primary frequency modulation is characterized by fast response, but only differential control can be realized. Secondary frequency modulation, also known as automatic generation control (AGC), means that the generator set provides enough adjustable capacity and a certain regulation rate to track the frequency in real time under the allowable regulation deviation to meet the requirements of system frequency stability. The secondary frequency modulation can realize the undifferentiated adjustment of frequency, and can monitor and adjust the power of tie line.

There are many ways to adjust the grid voltage, such as increasing the excitation of generators, generating multiple reactive power, adjusting cameras, reactive power compensators and so on.