Experiment No: 02
Name of the Experiment: Transient analysis of power system in MATLAB Simulink.
Objective: To perform a transient analysis of a simple power system using MATLAB
Simulink and observe the system's behavior following a sudden disturbance and to analyze
the resulting voltage and current waveforms.
Theory:
A power system is a dynamic network that operates in a steady state under normal
conditions. However, when a sudden change or disturbance occurs such as a short circuit,
switching operation, or lightning strike the system enters a transient state. During this
period, currents and voltages deviate significantly from their steady-state values as the
system adjusts to the new conditions. This analysis is critical for designing and
coordinating protective devices like circuit breakers and relays to ensure system stability
and equipment protection. MATLAB Simulink with the Simscape Electrical toolbox is an
ideal platform for this analysis, as it allows for the accurate modeling of power system
components and the simulation of dynamic events.
Apparatus:
1. Computer or Laptop – with MATLAB and Simulink installed
2. MATLAB and Simulink Software (R2023 version) – for modeling and simulation
3. Simulink Blocks Used:
i. AC Voltage Source
ii. Series R-L Branch (line resistance and inductance)
iii. Breaker
iv. RL Load
v. Voltage Measurement block
vi. Current Measurement block
vii. Scope
viii. Powergui block
Circuit Diagram:
Fig-1:Circuit Diagram of transient analysis of power system.
Output:
Fig-2:Response of the transient analysis of power system.
Result and Discussion:
In this simulation, a single-phase R–L network with a breaker was modeled using
Simulink’s Specialized Power Systems library. The scope outputs clearly illustrate three
stages of system behavior. At the very beginning (0–0.02 s), the voltage and current show
small oscillations or “ringing,” caused by the inductor–resistor elements responding to
initial conditions. Between 0.02 s and about 0.115 s, the breaker remains open, so the
measured voltage and current stay nearly flat at zero. Once the breaker closes at around
0.115 s, a sharp transient occurs because the switch is not synchronized with the voltage
zero crossing. After this short disturbance, the system settles into sinusoidal steady-state
operation. The load voltage appears as a clean sinusoid, while the current waveform also
becomes sinusoidal but lags behind the voltage, which is expected for an inductive load.
The amplitudes and phase relationship confirm the correct R–L impedance behavior. The
transient magnitude depends on the switching instant, and smoother results could be
obtained if the breaker were closed at a voltage zero-crossing or if the model were
initialized to steady state. The simulation, therefore, highlights the critical need for fast-
acting protective devices, such as circuit breakers, to detect and clear faults to prevent
equipment damage and maintain the stability of the power system.
The simulation required the powergui block, which is mandatory for Specialized Power
Systems models. Powergui provides the environment for solving the electrical network
equations and lets the user select between continuous or discrete modes. It also offers useful
analysis tools such as FFT, steady-state initialization, and impedance measurement. In this
case, the simulation was performed in continuous mode, which is best suited for accurate
time-domain representation of sinusoidal and transient waveforms. The solver used was
ode23tb (stiff/TR-BDF2), which is particularly effective for stiff systems such as R–L–C
networks with switching events. This solver automatically adjusts step size, shrinking
around the breaker closing to capture the transient accurately and expanding in steady state
for computational efficiency. It combines the stability of backward differentiation with the
accuracy of trapezoidal methods, making it one of the recommended solvers for power
electronics and switched circuit studies.
Precautions:
1.All the connections in the simulation were given carefully to avoid errors.
2.The components were selected properly from Simulink library.
3.The output was observed perfectly.
