On The Energy Fedback DUAL-PWM Speed Regulation System And The Coordinational Control Of Dynamic Loads

The dual-PWM speed regulation system is composed of a PWM rectifier and a PWMinverter. Due to its ability of bi-directional energy flow and high power factor, it has beenwidely used in many applications such as shipping, railway, wind power generation, and ironand steel processing machinery. In these applications, there are many dual-PWM systemsconnected to the same bus line to form an opening dual-PWM dymanic load group. Thegrouping and dynamic feature makes it difficult for the load groupto avoid mutual influencebetween different dual-PWM systems, and in some serious cases, it is even possible for thewhole load group to fall in failure.In order to solve the above-mentioned problems, a lot of research focused on thefollowing two aspects has been done in this paper: one is how to improve the controlperformance and anti-interference ability of the dual-PWM system; and the other is how tocontrol the dynamic load group coordinately so that the interaction between each load can belimited within an acceptable range, and avoid the occurrence of serious accidents. The detailsare as follows:Firstly, the principle of three-phase voltage source rectifier (VSR), the direct currentcontrol strategy and the direct power control strategy are studied. Based on the research of thedirect current control strategy, a simple and feasible parameter setting method which canimprove the anti-interference ability is proposed for three-phase VSR control system. In orderto enhance the robustness of the three-phase VSR control system, a control scheme combinedthe sliding-mode variable structure control and the direct power control (DPC) is proposed.Secondly, induction motor's vector control system and its theoretical parameter designmethod are studied. On the consideration of the defects of the theoretical design method, anapproach to tune the theoretical design parameters by referring to the parameter settingmethod of three-phase VSR is proposed.Thirdly, coordinating control algorithm of dual-PWM system is studied and amaster-slave control method is proposed. The proprosed control strategy will control the PWM rectifier's reactive power equal to0and the active power equal to the active power usedor regenerated by the PWM inverter, so that the pump voltage caused by the capacitance'scharge-discharge can be restrained effectively, and the dynamic response and anti-interferenceability of the dual-PWM system can be improved effectively.Lastly, the coordination control of the dual-PWM dynamic load group is studied. Basedon the mathematical model of dual-PWM dynamic load group, the mutual influence betweendifferent dual-PWM systems are anaylzed and the key problem of coordinatingcontrol—identification of the operation states of the dynamic load group is studied. A newapproach to solve this key problem is proposed, which employs the Short Time FourierTransform (STFT) to detect the amplitude and phase of the voltage of the bus line so that theexact load situation of the load group can be identified. Then based on the load identificationmodel, a coordination control algorithm for dual-PWM dynamic load group is proposed.This paper is sponsored by National Natural Science Foundation (50777022).