Transmission and distribution network reactive power/voltage control technology of large receiving-end urban power grid In recent years, as distributed generation, new loads and new FACTS devices widely access, high sensitive power users increasing, the existing automatic voltage control (AVC) technology of urban power grid have been unable to meet the new requirements under the new situation on the control objectives, control strategy and control means. In the aspect of control objectives, it only meets the reactive power balance of partition and voltage qualified rate of control bus, doesn't effectively reflect the user-end need of high quality power supply, therefore it is difficult to achieve the global optimal.

In the aspect of voltage control means, it have not covered the Reactive Power device of distribution and demand side; In the aspect of voltage control strategy, it focuses on the transmission network optimization, and the control strategy applicable to the special structure features of distribution grid has not been established.

Static Var Compensator SVC, Saturated reactor (SR) ,Thyristor-controlled reactor (TCR), Thyristor-switched capacitor (TSC) ,Thyristor-switched reactor (TSR) ,Thyristor control transformer (TCT), Self- or line-commutated converter (SCC/LCC) these existing methods are used to control the reactive power/voltage control. These controllers have their own advantages and disadvantages and applications of these controllers are limited.

To stabilize reactive power a new technique is to develop, the technique is based on the existing three-level voltage control, expand reactive voltage control of distribution and demand side, and fully meet the requirements of the user-end static and dynamic voltage quality.