The Coordinated Control Of Multi-machine System With Excitation System Based On Full Controlled Power Electronic Devices Rectifier

In China, the supply and demand of energy resources in the geographical distributionpresents the state of the reverse distribution, which determines the status quo anddevelopment trend of the regional power grid interconnection of power systems and alarge-scale long-distance power transmission in China. However, low frequency oscillationphenomenon and the impact it brings about on the power system severely restricted thedevelopment of the grid. For the weakness and disadvantage of the excitation system withthyristor rectifier which is widely used in current power system, the excitation system basedon full controlled power electronic devices rectifier, which can provide positive dampingfor the power system by regulating both the DC excitation current and injected reactivepower at the generator terminal to suppress low-frequency oscillations of the power system,is studied by some researcher. In this paper, the mathematics model and control strategy ofmulti-machine system with the excitation system based on full controlled power electronicdevices rectifier are studied.Firstly, the damping torque and its characteristics of the two damping channel in theexcitation system based on full controlled power electronic devices rectifier is analyzedon account of mathematics model of the single-machine infinite bus system. Then, themathematics model of the multi-machine system with the excitation system based on fullcontrolled power electronic devices rectifier is derived and its excitation controller isdesigned with the method of characteristic roots translation. The linear optimal controltheory is brought in to solve the coordination problem for the device with two dampingchannels. The linear optimal excitation controllers are designed respectively for thesingle-machine infinite bus system and multi-machine system with the excitation based onfull controlled power electronic devices rectifier. For the ultra-low-frequency oscillationphenomenon among the regional power grids of power system, combined with thedevelopment of the Wide Area Measurement System and Wide Area Control, dampingcontroller of multi-machine system with the excitation based on full controlled powerelectronic devices rectifier, which adopts the information from the Wide Area MeasurementSystem as its feedback sign, is designed. Meanwhile, the simulation and analysis for thevarious methods mentioned above are done, and the results of simulation proved that the designed controller is able to significantly suppress low-frequency oscillations of the powersystem and modify the operation of the power system, to improve the stability of powersystem.