Research On A Progressive-sequenced Optimization Control Method Of Reactive Power And Voltage Considering Voltage Stability

At present, regulation of reactive power and voltage power system is mainly realized by automatic voltage control (AVC). However, AVC can only carry on control according to the current operating state of the power network, it can not effectively work on coordinated control with multiple time scales and different types of reactive power sources. As a result, the reactive-power regulating devices act frequently and this affects the service life of the devices. Moreover,when the load is heavy, the voltage stability of the system is not good. But AVC is aimed at the the ecconomy of the power system so it can’t improve the stability of the system. Dynamic reactive power optimization contains action-number constraints of the transformer taps and compensation devices to avoid the control devicesfrom acting frequently with the load fluctuations.However, dynamic reactive-power optimization is equivalent to a reference control scheme before the day, it is not considering the impact brought fromthe error of short-term load forecasting. So the control scheme may not be reasonable.Moreover, the acting time scheme of discrete devices is not given. So it is necessary to study the dynamic coordinated optimization control method of reactive power and voltage in multiple time scales considering voltage stability.In this paper, the research on voltage stability is carried out firstly and a new voltage stability index based on voltage equation of the branch is proposed. The proposedindex is obtained by using the characteristic that the sensitivity of voltage to power at the voltage collapse point tends to be infinite. It can represent the voltage stability of the branch and simulations verify the effectiveness of the proposed on-line voltage index. Secondly, the reactive-power optimization of the single time section considering voltage stability is researched. The voltage stability index proposed in this paper is added to the optimization objective.The mathematical models are solved by primal dual interior point method with nonlinear complementary theory and the simulation is carried out only considering the current operating state. Thirdly, this paper puts forward a progressive-sequence optimization control strategy of reactive power and voltage. It is a coordinated optimization-control scheme in multiple time scales which means before the day, in the day and in real time. There are different optimization objective functions along with different segments of load according to the changing trend of the load. Besides the traditional optimization objective, which is the minimum of the power loss of the system, this paper takes the new voltage stability index and reactive power reserve into consideration. Meanwhile, in the optimization process, continuous variables and discrete variables are contained as well as action-number constraints of the discrete devices. The simulation results verify that the proposed method is effective.