Analysing the linear equivalent circuits of electromechanical systems for steam turbine generator units

The article utilises the analogy in dynamic equations between a mechanical and an electrical system to convert a turbine-generator mechanical model to an equivalent electrical circuit model. Based on the synchronous generator´s dynamic equations and the electromagnetic torque equation, an equivalent electrical interface circuit was derived. By using the interface circuit, the circuit model of synchronous generator and the equivalent electrical circuit model of turbine-generator mechanism can thus be combined into an integrated circuit model. The integrated circuit model is helpful for analysing the interactions between the mechanical and electrical systems for a steam turbine generator unit. Based on the integrated circuit model, the article has made a comparative study between a small and a large steam turbine-generator unit. The focus was on torsional mode frequencies, and the frequency scanning and eigen-analysing approaches were used. The result shows that torsional mode frequencies can be changed by means of the electromechanical integration. Moreover, the small unit was more affected than the large one.