Overview of the Power System Model
The simulation model presented for voltage regulation involves a STATCOM system connected to an AC grid. The voltage source is operating at 15 kV with a 60 Hz frequency, and the system consists of various components like source resistance, inductance, and two feeders. The feeders have different lengths, one being 21 km and the other 2 km, with a 3 MW real power load and a 2 MW reactive power load.
Additionally, there’s a bus that steps down the voltage from 15 kV to 600 V, where a 1 MW variable load is connected. This load is controlled with respect to time, ensuring that the voltage at the load stays constant at 600 V while maintaining a frequency of 60 Hz.
The Role of STATCOM in Voltage Regulation
The STATCOM system connects to the power system through a transformer and operates as a voltage source converter (VSC) and a capacitor. The main goal of the STATCOM is to ensure that the load voltage remains constant at 1 per unit, irrespective of fluctuations or deviations in the source voltage. By doing so, STATCOM helps in maintaining power quality and stability across the system.
How the STATCOM Controller Works
Inside the STATCOM controller, there are two key controllers: the AC voltage regulator and the DC voltage regulator. The AC voltage regulator monitors the AC side of the system, and the DC voltage regulator ensures the capacitor voltage is maintained within acceptable limits. These controllers work together to minimize voltage variations by adjusting their control signals based on the measured errors.
The error between the reference voltage and the actual voltage is fed into the PI controllers, where the proportional (KP) and integral (KI) parameters are fine-tuned to achieve the best control. This is where the PSO algorithm comes into play, optimizing these controller parameters for both AC and DC voltage regulation.
PSO Optimization for Controller Tuning
PSO, a popular optimization technique, is used to find the optimal values for the KP and KI parameters of the AC and DC voltage controllers. The objective is to minimize the absolute error between the reference voltage and the actual voltage, which results in improved voltage regulation.
In this approach, four variables are tuned: two for the AC voltage regulator and two for the DC voltage regulator. The PSO algorithm iterates over multiple cycles, updating the population and finding the best combination of parameters. After several iterations, the optimal values for the controller parameters are determined, leading to better performance in voltage regulation.
Simulation and Results
The PSO-based optimization process is simulated for 10 iterations, after which the best controller parameters are obtained. These values are used to simulate the power system’s behavior under different conditions, including voltage sags that occur during grid fluctuations.
The simulation results show that even in the presence of voltage sags (introduced at specific points during the simulation), the load voltage remains stable at 1 per unit, demonstrating the effectiveness of the STATCOM system in mitigating voltage deviations. The capacitor voltage also remains steady, thanks to the optimized PI controllers.
Conclusion: Improving Power Quality
In summary, using PSO-tuned PI controllers in a STATCOM system offers a highly effective solution for voltage regulation and power quality improvement. The ability of the system to maintain a constant load voltage despite fluctuations in the grid voltage showcases the potential of advanced control techniques in modern power systems.
By optimizing the control parameters through PSO, the STATCOM system is able to efficiently mitigate issues like voltage sag and maintain a steady supply of power. This ensures better stability and reliability for sensitive equipment and loads, making the approach ideal for real-world applications in power quality improvement.
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