# Verification Methodology for Simulation Models of the Synchronous Generator on Transients Analysis
## 3 Transient Analysis Using a Dynamic Simulation Model  
Electromagnetic transients were simulated on the model built in the MATLAB/Simulink/Simscape electrical software environment shown in Figure 7. The model is based on a real power network (a part of the Slovenian transmission system) and consists of several subsystems: hydropower plants HPP 1 and HPP 2, transmission lines, three-phase V-I measurements at the beginning and the end of each transmission line, three-phase sources, and a three-phase parallel RLC load. A transmission line was modeled by RL elements for each phase. The three voltage sources were connected in Y to an internal floating neutral. The load flow tool, which uses the Newton-Raphson method to provide a robust and fast convergence solution, was used to perform the load flow and for the initialization of  
Figure 5: Synchronous machine equivalent diagram for d-axis adapted with permission from ref. [1]. Copyright 2021 IEEE.  
Figure 6: Synchronous machine equivalent diagram for q-axis adapted with permission from ref. [1]. Copyright 2021 IEEE.  
three-phase networks and machines, so that the simulation starts in a steady state. For HPP 1, simulations were performed at no-load conditions. The generator type of the voltage sources was modeled to allow for control of the magnitude and the phase angle of the terminal voltage; the active power P and the reactive power Q were adjusted to allow the calculation to converge. The load type was set to constant PQ, i.e., active power and reactive power were kept constant and equal to the specified values, and the voltage angle was adjusted. The generator type of the synchronous machine was PV, i.e., active power and voltage magnitude were specified, and the voltage angle and the reactive power were adjusted. As a method to solve a circuit, discretization of the electrical system at the fixed time-step of 50 \(\upmu\)s was chosen.  
The influence of the short-circuit on the current-voltage conditions of the observed network was analyzed by simulating a three-phase short-circuit at the generator terminals in HPP 1, as shown in Figure 8. The three-phase fault block implemented a three-phase circuit breaker, where the opening and closing times were controlled.  
Figure 7: Network model for simulations in MATLAB/Simulink.  
The values of the parameters used for the synchronous generator model were: d-axis synchronous reactance \(X_{\text{d}}\) = 1.06 p. u., d-axis transient reactance \(X_{\text{d}}\)\({}^{\prime}\) = 0.28 p. u., d-axis subtransient reactance \(X_{\text{d}}\)\({}^{\prime}\) = 0.192 p. u., q-axis synchronous reactance \(X_{\text{q}}\) = 0.61 p. u., q-axis subtransient reactance \(X_{\text{q}}\)\({}^{\prime}\) = 0.176 p. u., leakage reactance \(X_{\text{l}}\) = 0.14 p. u., d-axis transient short-circuit time constant \(T_{\text{d}}\)\({}^{\prime}\) = 1.56 s, d-axis subtransient short-circuit time constant \(T_{\text{d}}\)\({}^{\prime}\) = 0.05 s, q-axis subtransient open-circuit \(T_{\text{q}}\)\({}^{\prime}\) = 0.09 s, inertia constant H = 3.2 s, friction factor F = 0, and stator resistance \(R_{\text{s}}\) = 0.0161 p. u.