Negative sequence droop method based hierarchical control for low voltage ride-through in grid-interactive microgrids

In highly microgrid (MG) integrated distribution systems, problems such as a sudden cut out of the MGs due to grid faults may lead to adverse effects to the grid. As a consequence, ancillary services provided by MGs are preferred since it can make the MG a contributor to ride through the faults. In this paper, a voltage support strategy based on negative sequence droop control, which regulate the positive/negative sequence active and reactive power flow by means of sending proper voltage reference to the inner control loop, is proposed for the grid connected MGs to ride through voltage sags under complex line impedance conditions. In this case, the MGs should inject a certain amount of positive and negative sequence power to the grid so that the voltage quality at load side can be maintained at a satisfied level. A two layer hierarchical control strategy is proposed in this paper. The primary control loop consists of voltage and current inner loops, conventional droop control and virtual impedance loop while the secondary control loop is based on positive/negative sequence droop control which can achieve power injection under voltage sags. Experimental results with asymmetrical voltage sags are conducted to verify the effectiveness of the proposed control strategy.

[1]  Hirofumi Akagi,et al.  Instantaneous Reactive Power Compensators Comprising Switching Devices without Energy Storage Components , 1984, IEEE Transactions on Industry Applications.

[2]  Donald Grahame Holmes,et al.  Stationary frame current regulation of PWM inverters with zero steady state error , 1999, 30th Annual IEEE Power Electronics Specialists Conference. Record. (Cat. No.99CH36321).

[3]  Josep M. Guerrero,et al.  Wireless-control strategy for parallel operation of distributed generation inverters , 2006, Proceedings of the IEEE International Symposium on Industrial Electronics, 2005. ISIE 2005..

[4]  G. Joos,et al.  Voltage support by distributed static VAr systems (SVS) , 2005, IEEE Transactions on Power Delivery.

[5]  J. Miret,et al.  Decentralized Control for Parallel Operation of Distributed Generation Inverters Using Resistive Output Impedance , 2005, IEEE Transactions on Industrial Electronics.

[6]  J.M. Guerrero,et al.  Hierarchical control of droop-controlled DC and AC microgrids — a general approach towards standardization , 2009, 2009 35th Annual Conference of IEEE Industrial Electronics.

[7]  Juan C. Vasquez,et al.  Voltage Support Provided by a Droop-Controlled Multifunctional Inverter , 2009, IEEE Transactions on Industrial Electronics.

[8]  S. Chowdhury,et al.  Microgrid: Control techniques and modeling , 2009, 2009 44th International Universities Power Engineering Conference (UPEC).

[9]  P. T. Krein,et al.  Review of the Impact of Vehicle-to-Grid Technologies on Distribution Systems and Utility Interfaces , 2013, IEEE Transactions on Power Electronics.

[10]  Frede Blaabjerg,et al.  Benchmarking of Grid Fault Modes in Single-Phase Grid-Connected Photovoltaic Systems , 2013, IEEE Transactions on Industry Applications.

[11]  Alon Kuperman,et al.  Proportional-Resonant Current Controllers Design Based on Desired Transient Performance , 2015, IEEE Transactions on Power Electronics.

[12]  Kai Zhang,et al.  Control and Monitoring for Grid-Friendly Wind Turbines: Research Overview and Suggested Approach , 2015, IEEE Transactions on Power Electronics.

[13]  Marta Molinas,et al.  Asymmetrical Fault Ride Through as Ancillary Service by Constant Power Loads in Grid-Connected Wind Farm , 2015, IEEE Transactions on Power Electronics.