Model Predictive Current Control for Fault-Tolerant Bidirectional Voltage Source Converter With Open Circuit Fault and Unbalanced Grid Voltage

Shiyang Hu,Leilei Guo,Nan Jin,Guorong Liu

doi:10.1109/access.2020.3018144

Abstract

To improve the fault-tolerant operation capability of bidirectional voltage source converter (BVSC), an improved model predictive current control (IMPCC) for fault-tolerant BVSC, is proposed with balanced DC-link capacitor voltage under unbalanced grid voltage. The proposed method can maintain continuous operation even if power device faults and unbalanced grid voltage faults occur together. A current predictive model of the fault-tolerant BVSC is established. By using grid voltages and 90° lagging signals in the $\alpha \beta $ stationary coordinate system, the reference current calculation method is designed for BVSC to eliminate power ripple under unbalanced grid voltage, which can avoid the complex positive and negative sequence extraction. DC-link split capacitor voltage balancing is achieved by the improved cost function. Based on the current predictive model and improved cost function, the optimal space voltage vectors are selected for fault-tolerant BVSC. Compared to the existing predictive methods, the proposed IMPCC can balance DC-link capacitor voltage and eliminate the power ripples for fault-tolerant BVSC under unbalanced grid with simple implementation. The experimental results validate the effectiveness of the proposed control scheme.

Highlights

The main goal of the fault-tolerant power converter is to work continuously even with reduced performance when converter faults occur during normal operation
The control schemes of three-phase four-switch (TPFS) are classified into two categories: modulation based linear control and nonlinear control
The vector pulse width modulation (PWM) strategy for TPFS inverters can select three or four vectors by space vector modulation. These fault-tolerant methods of the TPFS converter rely on the PWM control method [8,9], which needs coordinates transformation and modulation module with complex algorithms

Summary

INTRODUCTION

The main goal of the fault-tolerant power converter is to work continuously even with reduced performance when converter faults occur during normal operation. An improved model predictive direct power control (MPDPC) for PWM rectifiers is proposed in [13] These methods require the phase-locked loop (PLL), positive and negative sequence extraction. An improved model predictive current control (IMPCC) method is proposed for fault-tolerant BVSC to reduce current harmonic distortion and power ripples under the conditions of switch open circuit and unbalanced grid voltages. When the phase leg faults and unbalanced grid conditions occur, the fault-tolerant BVSC can keep continuous operation, which improves the reliability of the bidirectional power conversion. NONREDUNDANT FAULT-TOLERANT BVSC MODEL In this paper, the control scheme of BVSC with an open circuit or short circuit faults of power devices in a phase leg is studied. Where e , eβ, e , eβ , i , iβ, i , iβ are grid voltage, current, and the 90°lagging signals, where the sequence extraction and PLL are not needed

DC-LINK SPLIT CAPACITOR VOLTAGE BALANCE CONTROL

COST FUNCTION WITH DELAY COMPENSATION

EXPERIMENT VERIFICATION

Findings

CONCLUSION