The frequency characteristic of the power system depends on the frequency characteristic of the load and the frequency characteristic of the generator. Characteristics), which is determined by the active load balance of the system and has little to do with the network structure (network impedance). In the case of non-oscillation, the steady-state frequency of the same power system is the same. Therefore, the system frequency can be adjusted and controlled centrally. The voltage characteristics of the power system are different from the frequency characteristics of the power system. The voltage of each node of the power system is usually not exactly the same, mainly depends on the balance of active and reactive power supply and demand in each zone, and also has a greater relationship with the network structure (network impedance). Therefore, the voltage cannot be adjusted uniformly in the whole network, but can only be adjusted and controlled by partition.