Research On Dynamic Characteristic And Control Strategy Of StatCom In Power Distribution Systems

This paper described the StatCom of distribution to power systems. The typical objects of distribution StatCom are node-voltage stability, reactive power compensation, dynamic characteristics for special loads, such as oil-pump motor in oil-field, in addition, harmonics reduction. The first two or three objects are main points described in this paper. StatCom applications in power systems is an attempt to solve the conflict between daily increased power consumers and the finite source of power networks, at the mean time, to solve power quality problems caused by a large number of nonlinear new power equipments and other reasons. The effect of StatCom or other FACTS controller has been proved successfully. It shows also very economically and practically. FACTS have replaced, or are replacing traditional power facilities, and plays important role in power transmission, distribution and power usages. At the first, it describes the history, survey, and the functions of FACTS in this paper. Besides StatCom, the basic working principles of other common FACTS controllers and theirs differences between configuration and corresponding theories are also expressed. Detail explanation for obscure term, such as concept of "power quality", has been made in accordance to international standards; the famous practices of important FACTS in the word, especially the StatCom, are enumerated with explanation as detailed as possible. In fact, it has presented the latest development in the research field of FACTS in this part. The fundament principle of compensation and voltage stability with StatCom are described in this paper. The StatCom terminologies of transmission and distribution systems are clearly expressed for the first time in this paper. Normally speaking, the voltage level and compensation capacity of transmission StatCom is higher than that of distribution StatCom; but the distribution StatCom should reduce harmonic pollution produced by load besides its normal functions, and it should respond quick enough while the harmonic and reactive power variation caused by load vary sharply under operation. There are some common control objects to both StatCom, and there are also some distinctive to each other. To be familiar with the control and system parameters to distribution systems is very important in order to complete normal function for distribution StatCom. The relationship between parameter's variation and operation characteristics of StatCom is described; some suggestions for the proper selection of parameters are proposed at mean time.Practically speaking, the dynamic and steady state characteristics of StatCom are very important. The research and analysis of the operation principal and dynamic process for StatCom have been made, especially for the typical configurations of two-level and dual three-point inverter. The control strategy inner-nested with DC-link voltage is proposed in this paper. From the view of control strategy, although there are many other control strategies used for StatCom control, which have some same control objects also with each other, it presents some distinctive compared with dual-loop feed-back control strategy formed with line current and voltage, it has difference with so-called virtual-flux control and other control strategies also. In the control strategy, voltage control loop is in inloop, whereas the reactive power loop is in outloop, so it can regulate node voltage very quickly, and control reactive power with relative more time, but the two objects mentioned above can be realized overall. The simulation results indicate that the node-voltage could enter steady state within 20ms, and reactive power in 3 periods, when there is a prompt disturb of load reactive power.The parameter selection to DC-link is difficult to deal with in the StatCom research, especially with different circuit configurations. The DC capacitor for voltage-sourced inverter (VSI) is normally conservatively selected, it leads to higher capacity, larger volume, and not economical. Derived from the math...