Analysis of Fractional Order Sliding Mode Control in a D-STATCOM Integrated Power Distribution System

Toqeer Ahmed,Umashankar Subramaniam,Manoharan Premkumar,Rajvikram Madurai Elavarasan,Asad Waqar,Junaid Imtiaz

doi:10.1109/access.2021.3078608

Abstract

At present, the disturbances like the voltage fluctuations, resulting from the grid’s complexities and unbalanced load conditions, create severe power quality concerns like total harmonic distortion (THD) and voltage unbalance factor (VUF) of the grid voltage. Though the custom power devices such as distribution-static compensators (D-STATCOMs) improve these power quality concerns, however, the accompanying controller plays the substantial role. Therefore, this paper proposes a fractional-order sliding mode control (FOSMC) for a D-STATCOM to compensate the low power distribution system by injecting/absorbing a specific extent of the reactive power under disturbances. FOSMC is a non-linear robust control in which the sliding surface is designed by using the Riemann-Liouville ( RL ) function and the chattering phenomenon is minimized by using the exponential reaching law. The stability of FOSMC is evidenced by employing the Lyapunov stability criteria. Moreover, the performance of the proposed FOSMC is further accessed while doing its parametric variations. The complete system is demonstrated with a model of 400V, 180kVA radial distributor along with D-STATCOM under two test scenarios in MATLAB/Simulink environment. The results of the proposed controller are compared with the fixed frequency sliding mode control (FFSMC) and conventional proportional-integral (PI) control. The results validate the superiority of the proposed controller in terms of rapid tracking, fast convergence, and overall damping with very low THD and VUF.

Highlights

In the power distribution system, power quality implies to keep the AC bus sinusoidal voltage waveform at the measured voltage and frequency [1]
D-STATCOM sustains the voltage at LV AC bus by injecting/absorbing a certain extent of reactive power in both cases
It can be observed that the voltage total harmonic distortion (THD) and voltage unbalance factor (VUF) of proposed fractional-order sliding mode control (FOSMC) during unbalanced load conditions result in 0.97% and 0.0014% in contrast to fixed frequency sliding mode control (FFSMC) and PI control and are well under the IEEE standards which verifies the competency and exceptional performance of FOSMC

Summary

INTRODUCTION

In the power distribution system, power quality implies to keep the AC bus sinusoidal voltage waveform at the measured voltage and frequency [1]. The authors in [21], have proposed a CSC-based DSTATCOM which utilizes the minimum DC voltage for the reactive power compensation to eliminate the harmonics and reduces the switching losses using the PI control. In [27], the authors have proposed a PI control for parallel operation among D-STATCOMs for the reactive power-sharing, and to compensate the harmonics resulting from the non-linear load. In [42], a shunt connected D-STATCOM is investigated in the power distribution system to compensate the reactive power required for load balancing They proposed an SRLMMN control for fast convergence and to reduce steady-state error. The authors in [46], have proposed a capacitor-less D-STATCOM based on MC by employing FCS-MPC for reactive power compensation under non-linear load conditions. Current Reference Generator idref, iqref sliding surface (d-axis) sliding surface (q-axis)

STABILITY ANALYSIS

SYSTEM BASED ANALYSIS AND RESULT DISCUSSIONS

Steady State Performance and FOSMC Parameters Selection

Performance Evaluation Under Unbalanced Load Conditions

Findings

CONCLUSION