Abstract
Accuracy system model and its parameters are of great importance in stability and security evaluation or simulation for power systems. The electro-hydraulic servo and actuator is one of the most important components in the system. A mathematical model for the electro-hydraulic servo and actuator system developed on the working principle of each component has model parameters with clear physical meanings that can be obtained from field test data. The model is validated by data from four reheat turbines with different digital electro-hydraulic (DEH) control systems. Simulations show that the model agrees well with the test data when the servo cards are either proportional or proportional integral controllers. The results also show that the IEEE model parameters can be derived by this model.