Improved Current Decoupling Method for Robustness Improvement of LCL-type STATCOM Based on Active Disturbance Rejection Control

Minglei Wang,Liguo Wang,Jinxin Qiao,Xiangyu Wang

doi:10.1109/access.2019.2931747

Abstract

When theoretically studying the control method of LCL-type static synchronous compensator (STATCOM), we often ignore the influence of complex power grid on the stability and reactive compensation performance of STATCOM. Improving traditional current decoupling method with PI controller (PI decoupling) in synchronous (dq) reference frame, an original current decoupling method with active disturbance rejection controller (ADRC decoupling) is proposed in this paper. First, the influence of internal and external disturbances on STATCOM with PI decoupling method is analyzed. External disturbances include harmonic grid voltage and grid inductance variation. Internal disturbances come from coupled channels between d axis and q axis, and parameter perturbations of LCL filter. Second, the principle of ADRC decoupling method applied to LCL-type STATCOM is analyzed in detail. Taking advantage of ADRC's capability to estimate and compensate for the “total disturbances”, robustness of STATCOM is improved. Comparing with PI decoupling method, ADRC decoupling method can improve the disturbances rejection performance and stability of LCL-type STATCOM. Finally, results from STATCOM simulation model show the effectiveness and superiority of this original method.

Highlights

STATCOM is utilized to compensate reactive power and stabilize the voltage at the point of common coupling (PCC) [1], [2]
Compared with the L filter, the LCL filter has better performance to filter high order harmonic current, but its coupled channels between d axis and q axis are more complex in synchronous reference frame
Decoupling method with Active disturbance rejection controller (ADRC) can remove the coupled channels of controlled system with multiple inputs and multiple outputs, and it can improve the robustness for LCL-type STATCOM to reject internal and external disturbances

Summary

INTRODUCTION

STATCOM is utilized to compensate reactive power and stabilize the voltage at the point of common coupling (PCC) [1], [2]. Traditional PI decoupling method for LCL-type STATCOM is unstable under the influence of power grid disturbances [3]. Current decoupling control method has higher control accuracy, shorter dynamic response time and better disturbance rejection performance by removing the coupled channels [8], [5], [20]–[22]. Decoupling method with ADRC can remove the coupled channels of controlled system with multiple inputs and multiple outputs, and it can improve the robustness for LCL-type STATCOM to reject internal and external disturbances. ADRC decoupling method is applied for LCL-type grid-connected inverter to achieve independent control of active current and reactive current. Traditional PI decoupling method with large computation is difficult to obtain excellent control effect under the influence of the internal and external disturbances

ANALYSIS OF INTERNAL AND EXTERNAL DISTURBANCES

EFFECT ANALYSIS OF ADRC ON LCL-TYPE STATCOM

Findings

CONCLUSION