Power System Blockset | ![]() ![]() |
Simulation Results
The performance of the nonlinear controller is tested on the nonlinear turbine-generator system. The controller and turbine are simulated using Simulink blocks while the generator is represented by the Synchronous Machine block from the powerlib library. A three-phase short-circuit is simulated on the load busbar and the fault is cleared after 100 ms. The performance of the nonlinear controller is analyzed.
The case study is included in the psbregulator.mdl
file. The system is illustrated in Figure 2-18 below. Before running the simulation, make sure that the simulation parameters are set as follows:
ode23tb;
Maximum order: 5
1.0
auto;
Initial step size: auto
1e-3;
Absolute tolerance: auto
psbregulinit
Figure 2-18: Simulink Diagram of Case Study (psbregulator.mdl
)
Due to nonlinearities present in this system, computation of initial conditions was not carried out. Instead, a long simulation (10 s) was executed and the final states saved in file psbreguldata.mat
. These final states are used as initial states in this case study. The simulation consequently starts in steady-state. At t=0.1s, the fault is suddenly applied and removed after 100 ms (6 cycles). The post-fault transient is then observed.
The nonlinear controller calls a MATLAB initialization function to compute the gains before the simulation. Although this process has been automated to take into account the parameters in the dialog boxes of the various blocks, it is not recommended that you change any value in any block.
If you decide to change some values, a long simulation must be run and the final states must be in a file called psbregulinit.mat
. Figure 2-19 shows the response of the generator's terminal voltage, load angle, and the control effort of the regulator. You can observe how the stabilization of Vt is obtained in less than 0.25 seconds with this controller. The load angle takes longer to stabilize, because the time constant of the mechanical part of the system is much larger than the electrical time constants. If you want to compare results with classical regulators, replace the nonlinear controller with the same excitation system and Hydraulic Turbine and Governor block used in the psbturbine
demo. You will notice that the system takes longer to stabilize than in this case study.
Figure 2-19: Simulation Results Obtained With Case Study
References
[1] Akhrif O., F.A. Okou, L.A. Dessaint, and R. Champagne, "Application of a Multivariable Feedback Linearization Scheme for Rotor Angle Stability and Voltage Regulation of Power Systems." IEEE Transactions on Power Systems, Vol. 14, No. 2, May 1999, pp. 620-628.
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