Dynamics And Control Of Electronic Cascaded Systems

Electronic Cascaded Systems are complex systems integrated by different powerelectronic converters. This topology has the advantage of flexibility, augment abilityand redundancy. In recent years, such designs are wide used in automotive powersystems, Electric and Hybrid Electric Vehicles, advanced industrial electrical systems,telecommunications, terrestrial computer systems, International Space Station,spacecraft, More Electric Ship power systems, military affairs and so on. Usuallyeach module is designed based on its own stand-alone operation. There could bepotential interaction in such systems when the modules are integrated together. So theresearch on stability of Electronic Cascaded Systems shows the significance. This study analyzes most of the important issues of stability problems in ElectronicCascaded System with the power system of Electric Vehicle (EV). The organizationof this study is as follows: Multi-level modeling concept is depicted in this paper. By using average modelingmethod, Park's equation and small signal analysis, the model of boost converter,three-phase voltage source inverter and two kinds of filters are obtained. The transferfunctions are given according to their models. Simulation model by the stateequations of each block carried out in Matlab. For the importance of Boost converterand Motor Drive System, models are carried out by units of SimPowerSystems.Impedance Ratio Criterion is depicted to determine the stability of ElectricCascaded system. The open-loop stability is given. The effects of different loadcharacteristic to the system are analyzed, and the stabilizing qualifications with linearcontrol technique are developed. After that, a novel method to calculate the close-loopimpedance, which must base on the proper design of each module, is developed. Theequivalent negative impedance of motor system working as constant power load isdescribed in detail. Then the close-loop system stability which shows the potentialinteraction is obtained, and simulations prove the conclusion.The improvements of system stability from different methods, which containpower stage parameters configuration, media filter design, control technique design ofBoost converter and inverter, are proved with simulations. The methods of parallelingcapacitor on dc bus and designing feed-forward control technique of motor drive arechosen to prove the effects according to the experiment condition. The rated power ofBoost converter is 150kW and the motor drive system used in Electric Vehicle is100/160kW. The experiments show that combining use of improvement methods notonly can reduce the ripple of dc bus, but also can increase the efficiency of system.The engineering applications of impedance criterion are introduced byMeasurement of impedance and online measurement of stability margin. A method ofsubstitute impedance criterion for faster stability determination of cascading isdeveloped.This paper provides a valuable complete set of design scheme of system stabilityanalysis, improvement and engineering application for Electronic Cascaded Systems.