Abstract

Modular multilevel converter (MMC) is drawing more and more attention in medium-voltage microgrid applications. Large-scale switching-off loads and grid faults may lead to the voltage swell in microgrid, where MMC should have the ride-through ability. In this paper, a simple operation approach with the fundamental and irregular zero-sequence voltage (ZSV) injection is proposed for MMC under grid voltage swell condition. First, the fundamental ZSV injection is applied to adjust the modulation margin of three phases where the amplitude values of modulation waves in each phase can be the same. Then, if the amplitudes with fundamental ZSV injection are still in over-modulation status, the new irregular ZSV injection is added to further enlarge the operation region. In addition, the limitation of the irregular ZSV injection is analyzed. Simulation and experimental results of MMC under different grid voltage swell conditions verify the effectiveness of the proposed operation approach.

Highlights

  • The rapid penetration of renewable energy, such as wind power and solar energy, dramatically draw more attention and changes in modern distributed power system and microgrid [1]–[3]

  • Modular multilevel converter (MMC) has been widely applied in various applications such as voltage source converter (VSC) based high voltage direct current (HVDC) [8], STATCOM [9], motor drive [10], DC ship microgrid [11], energy storage system [12] and power electronic transformers [13]

  • It should be noted that this paper focuses on the operation approach after the detection of the grid voltage swell

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Summary

INTRODUCTION

The rapid penetration of renewable energy, such as wind power and solar energy, dramatically draw more attention and changes in modern distributed power system and microgrid [1]–[3]. Q. Xiao et al.: Simple Operation Approach for MMC Under Grid Voltage Swell in Medium-Voltage Microgrids growth of wind power capacity and improvement of the grid connection standards [15]. A vector hysteresis controller is adopted during the grid voltage swell, which provides a good dynamic response of the current controller and provides the HVRT ability for grid-connected converter [24]. Another fault ridethrough operation scheme for two-level converter under grid voltage swell is presented with a modified space vector modulation (SVM) [25].

TOPOLOGY OF MMC
EQUIVALENT CIRCUITS OF MMC
OVERALL CONTROL MODEL
PROBLEM OF GRID VOLTAGE SWELL
FZSV INJECTION AND ANALYSIS
IRREGULAR ZSV INJECTION WITH HIGHER OPERATION RANGE
SIMULATION RESULTS
CONCLUSION
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