DC-Link Protection and Control in Modular Uninterruptible Power Supply

In this paper, a dc-link voltage protection (DCVP) control method is proposed to address the dc-link overvoltage issue due to power backfeeding in a parallel uninterruptible power supply (UPS) system. The proposed control method is able to protect the inverter against the excessive dc-link voltage, which increases the system reliability and robustness. Moreover, a current sharing control strategy is proposed by online regulating the virtual resistance of each UPS module. The proposed current sharing control strategy is able to address the circulating fundamental and harmonic currents caused by the line impedance mismatching or power backfeeding issue in the UPS system. In addition, an improved consensus-based distributed controller is proposed to alleviate the overshoot issue during the transient process in voltage amplitude and frequency restoration. Finally, the feasibility of the proposed methods is verified by experimental results from the parallel UPS prototypes.

[1]  Thomas Seel,et al.  Voltage Stability and Reactive Power Sharing in Inverter-Based Microgrids With Consensus-Based Distributed Voltage Control , 2016, IEEE Transactions on Control Systems Technology.

[2]  Juan C. Vasquez,et al.  Distributed Secondary Control for Islanded Microgrids—A Novel Approach , 2014, IEEE Transactions on Power Electronics.

[3]  Ernane Antônio Alves Coelho,et al.  Small signal stability for single phase inverter connected to stiff AC system , 1999, Conference Record of the 1999 IEEE Industry Applications Conference. Thirty-Forth IAS Annual Meeting (Cat. No.99CH36370).

[4]  Richard M. Murray,et al.  Asynchronous Distributed Averaging on Communication Networks , 2007, IEEE/ACM Transactions on Networking.

[5]  Dehong Xu,et al.  Modeling, analysis, and implementation of parallel multi-inverter systems with instantaneous average-current-sharing scheme , 2003 .

[6]  Zhaoan Wang,et al.  Auto-master-slave control technique of parallel inverters in distributed AC power systems and UPS , 2004, 2004 IEEE 35th Annual Power Electronics Specialists Conference (IEEE Cat. No.04CH37551).

[7]  Rajani Gn.  Emerging trends in Uninterrupted Power Supplies: Patents view , 2016 .

[8]  Po-Tai Cheng,et al.  Evaluation of PWM Methods for Suppressing Circulating Current Among Parallel-Connected Four-Pole Inverters , 2015, IEEE Transactions on Industry Applications.

[9]  Juan C. Vasquez,et al.  Hierarchical Control of Droop-Controlled AC and DC Microgrids—A General Approach Toward Standardization , 2009, IEEE Transactions on Industrial Electronics.

[10]  Juan C. Vasquez,et al.  Multiagent-Based Distributed State of Charge Balancing Control for Distributed Energy Storage Units in AC Microgrids , 2017, IEEE Transactions on Industry Applications.

[11]  Fei Wang,et al.  A Control Strategy for Suppressing Circulating Currents in Parallel-Connected PMSM Drives With Individual DC Links , 2016, IEEE Transactions on Power Electronics.

[12]  M. Schwab,et al.  New inverter module with digital control for parallel operation , 2000, TELESCON 2000. Third International Telecommunications Energy Special Conference (IEEE Cat. No.00EX424).

[13]  Xu Dianguo,et al.  Bandwidth Expansion Method for Circulating Current Control in Parallel Three-phase PWM Converter Connection System , 2014, IEEE Transactions on Power Electronics.

[14]  M.S. Racine,et al.  An overview of uninterruptible power supplies , 2005, Proceedings of the 37th Annual North American Power Symposium, 2005..

[15]  Masahiro Kinoshita,et al.  Redundant, High Density, High Efficiency Double Conversion Uninterruptible Power System , 2009, 2009 IEEE Industry Applications Society Annual Meeting.

[16]  Josep M. Guerrero,et al.  Modular Plug’n’Play Control Architectures for Three-Phase Inverters in UPS Applications , 2016 .

[17]  W. Khan-ngern,et al.  Design of the Two Parallel Inverter Modules by Circular Chain Control Technique , 2007, 2007 7th International Conference on Power Electronics and Drive Systems.

[18]  Josep M. Guerrero,et al.  Fast Reactive Power Sharing, Circulating Current and Resonance Suppression for Parallel Inverters Using Resistive-Capacitive Output Impedance , 2016, IEEE Transactions on Power Electronics.

[19]  Juan C. Vasquez,et al.  Control Architecture for Parallel-Connected Inverters in Uninterruptible Power Systems , 2016, IEEE Transactions on Power Electronics.

[20]  G. N. Rajani.  Emerging trends in Uninterrupted Power Supplies: Patents view , 2016, 2016 Biennial International Conference on Power and Energy Systems: Towards Sustainable Energy (PESTSE).

[21]  Masahiro Kinoshita,et al.  Redundant High-Density High-Efficiency Double-Conversion Uninterruptible Power System , 2010 .

[22]  Mehdi Savaghebi,et al.  Modeling, Analysis, and Design of Stationary-Reference-Frame Droop-Controlled Parallel Three-Phase Voltage Source Inverters , 2013, IEEE Transactions on Industrial Electronics.

[23]  Yinliang Xu,et al.  Distributed Optimal Resource Management Based on the Consensus Algorithm in a Microgrid , 2015, IEEE Transactions on Industrial Electronics.

[24]  Francisco A. S. Neves,et al.  Modulation Techniques to Eliminate Leakage Currents in Transformerless Three-Phase Photovoltaic Systems , 2010, IEEE Transactions on Industrial Electronics.

[25]  Ernane Antônio Alves Coelho,et al.  Small signal stability for parallel connected inverters in stand-alone AC supply systems , 2000, Conference Record of the 2000 IEEE Industry Applications Conference. Thirty-Fifth IAS Annual Meeting and World Conference on Industrial Applications of Electrical Energy (Cat. No.00CH37129).

[26]  Juan C. Vasquez,et al.  A Dynamic Consensus Algorithm to Adjust Virtual Impedance Loops for Discharge Rate Balancing of AC Microgrid Energy Storage Units , 2018, IEEE Transactions on Smart Grid.

[27]  Yun Wei Li,et al.  An Enhanced Microgrid Load Demand Sharing Strategy , 2012, IEEE Transactions on Power Electronics.

[28]  Juan C. Vasquez,et al.  Modular Online Uninterruptible Power System Plug‘n’Play Control and Stability Analysis , 2016, IEEE Transactions on Industrial Electronics.

[29]  Josep M. Guerrero,et al.  A Circulating-Current Suppression Method for Parallel-Connected Voltage-Source Inverters With Common DC and AC Buses , 2017, IEEE Transactions on Industry Applications.

[30]  Frede Blaabjerg,et al.  Multiresonant Frequency-Locked Loop for Grid Synchronization of Power Converters Under Distorted Grid Conditions , 2011, IEEE Transactions on Industrial Electronics.

[31]  Juan C. Vasquez,et al.  Control Strategy for Flexible Microgrid Based on Parallel Line-Interactive UPS Systems , 2009, IEEE Transactions on Industrial Electronics.

[32]  Lorenzo Giuntini.  Active damping control of multi-mode UPS for power quality improvement , 2015, 2015 17th European Conference on Power Electronics and Applications (EPE'15 ECCE-Europe).

[33]  Li Li,et al.  A Frequency-Fixed SOGI-Based PLL for Single-Phase Grid-Connected Converters , 2017, IEEE Transactions on Power Electronics.

[34]  Mehdi Savaghebi,et al.  Distributed Voltage Unbalance Compensation in Islanded Microgrids by Using a Dynamic Consensus Algorithm , 2016, IEEE Transactions on Power Electronics.

[35]  Frede Blaabjerg,et al.  An Enhanced Islanding Microgrid Reactive Power, Imbalance Power, and Harmonic Power Sharing Scheme , 2015, IEEE Transactions on Power Electronics.