Research on Multilevel Reactive Power and Voltage Control of Active Distribution Networks

With the access of large amount of distributed PVs to the distribution network, the overvoltage becomes the key factor that affects the operation security and stability of power grid. In order to adapt to the high permeability and large-scale access of distributed PVs to power grid, and to improve voltage regulating ability of system, a multilevel reactive power and voltage control strategy for active distribution network is proposed by classification according to the different characteristics of the voltage resources in the active distribution network. The proposed control strategy can achieve the first, second, third and fourth-level voltage regulation based on small-capacity distributed PV, reactive power of PV, traditional VQC device and active power of PV. The decentralized local control strategy is applied to control small-capacity distributed PV, by which the control model of cosφ(U、P) is proposed based on voltage and PV active power output. In the end, taking the modified IEEE33-bus system as example, the simulation result shows that the proposed four-level voltage regulation strategy makes full use of distributed voltage resources in the active distribution network, action times of the VQC device is reduced effectively, and the voltage level of network is improved.