Power System Protection and Control Using LCL Filtering in DVR Compensation: Transformer Leakage Reactance Determination
Authors: Wu Fuzhuo, Hou Tingting, Han Liang (Zhongyuan Institute of Technology, Zhengzhou 450007, China)
This study focuses on the application of LCL filters in Dynamic Voltage Restorer (DVR) systems to enhance power quality and system stability. The DVR compensates for voltage sags and swells, ensuring uninterrupted power supply to sensitive loads. An essential aspect of this setup involves determining the leakage reactance of the series compensation transformer.
An LCL filter comprises an inductor-capacitor-inductor configuration that filters out high-frequency switching noise produced by inverters. This study analyzes how the leakage inductance of the transformer can serve as part of the LCL filter. The filter's design aims to minimize harmonic distortions and maintain the integrity of the grid voltage.
The LCL filter's parameters must meet several criteria: they need to support active and reactive power control, comply with harmonic current limits, and facilitate accurate current tracking. The inductance values directly impact the filter's performance, influencing the ripple current and overall stability of the system.
For a 30 kVA DVR, simulations were conducted using specific LCL filter components: an inductor (Li) of 3 mH, a capacitor (Cf) of 15 µF, and a transformer leakage inductance (La) of 0.04 mH. These settings resulted in an impedance drop of 0.19 V, representing approximately a 1% voltage drop. The harmonic distortion rate of the compensation voltage was 16.34%, while the THD of the grid voltage was 1.80%.
In scenarios where the grid voltage dropped by 30%, other parameters remaining constant, the harmonic distortion rate of the compensation voltage decreased to 5.71%, with the grid's THD at 1.65%. This indicates that as the voltage sag increases, the relative contribution of the compensation voltage diminishes, leading to lower harmonic distortion rates overall.
From these simulations, we observe that the designed filter inductor and transformer leakage inductance yield favorable practical outcomes. Combining the transformer's leakage inductance with the LC filter creates an effective LCL filter circuit. Through stability, current tracking, and filtering performance analyses, the method proves its validity, supported by both simulation and experimental evidence.
In conclusion, the integration of the transformer's leakage inductance with the LCL filter offers an economical and efficient solution for power system protection and control. This approach not only enhances the resilience of the power grid against disturbances but also optimizes the economic feasibility of DVR systems, ensuring reliable power delivery to critical loads. Future work could explore further refinements in parameter optimization and real-world implementation challenges to maximize the benefits of this technology.
Servo Electric Cylinder,Linear Actuator With Speed Control,Parallel Drive Linear Actuators,Long Stroke Electric Linear Actuator
Suzhou Johnson Automation Technology Co., Ltd. , https://www.cn-johnson.com