Research On SCR Static Frequency Converter Control Technology For Pumped Storage Unit

The pumped storage plants, which has many abilities such as frequencyadjustment, hydropower modulation, phase modulation peaking and valley fillingand emergency reserve, has become a flexible regulatory approach of modern grids.Nowadays, almost all pumped-storage plants adopt reversible hydroelectric units. Inother word, it means that the water turbine drives the generator to supply power toextract water from downstream to upstream to storage when it works at generationworking condition. This makes the pumped-storage units’ working conditions verycomplicated, especially the starting of pumped-storage unit. The large capacity andgreat inertia of the units or any other reasons makes control unit synchronizationstarting a difficulty. This paper makes a full exposition of the non-position SCRstatic frequency conversion starting process of the pumped-storage machine. Itmakes deep theoretical analysis of the control mode of SCR static frequencyconverter with non-position detection. And use simulation and experiment platformto prove that SCR static frequency converter can be used to start synchronous motor.First of all, it studies and analyzes the principle and the merits and demerits ofevery topological structure of SCR static frequency converter. Additional, it alsodescribes operating principles in detail including natural commutation andintermittent commutation of SCR static frequency converter. At the same time, twocommutations mode switching method and control strategy of SCR static frequencyconverter studied in EMF commutation stage are analyzed.Secondly, on the basis of synchronous motor’s seven stages mathematicalmodel, it simplifies the model and built five stages mathematical model. Meanwhile,as for the model, simulation is made by taking advantage of Matlab/Simulink. Bymaking use of motor model, mathematical modeling and simulation verifyoperational state to every startup phase of SCR static frequency converter.Last, on account of adopting intermittent commutation in its low order, thegenerator terminal in synchronous motor has a large number of harmonic. It leads indifficulty of rotor position calculation. Thus, this paper studies flux linkage observer.On the foundation of analyzing operating principle of traditional flux linkageobserver, it improves and adopts filter after compensation mode to decrease fluxlinkage observing error and makes simulation. In the meanwhile, it redesign fluxlinkage observer, which operational principle is filter after compensation, and givesstructure diagram. Combined with simulation, the optimized cut-off frequencysetting value is given.For simulating the pumped-storage units experimental platform, experimental platform is build by control target10kW synchronous motor. The experimentverifies every start-up phase of pumped storage units. During application of electricfield,0.5~5Hz position detect more accurate, which phase difference is less than5°.On this position, all start-up requirements in experimental condition can be met. Italso can realize smooth switch between intermittent commutation and naturalcommutation.