Analytical evaluation of DC capacitor RMS current and voltage ripple in neutral-point clamped inverters

The sizing of the DC-link capacitor in a three-level inverter is based on the RMS current flowing through it. This paper analyses the DC-link capacitor RMS current in a neutral-point clamped (NPC) inverter and expresses the same as a function of modulation index, line-side current amplitude and power factor. Analytical closed-form expressions are derived for the capacitor RMS current for single-phase half-bridge, single-phase full-bridge and three-phase three-leg topologies of a three-level inverter. The worst-case capacitor current stress is determined for each topology based on the analytical expressions. Further, analytical expressions are derived for the RMS values of low-frequency and high-frequency capacitor currents. These expressions are then used to estimate voltage ripple across the DC capacitor for sinusoidally modulated three-phase NPC inverter. The analytical expressions for the RMS current and voltage ripple are validated experimentally over a wide range of operating points.

[1]  S. Bernet,et al.  A comparison of three-level converters versus two-level converters for low-voltage drives, traction, and utility applications , 2005, IEEE Transactions on Industry Applications.

[2]  Suleiman M. Sharkh,et al.  Analysis of dc-link capacitor current in three-level neutral point clamped and cascaded H-bridge inverters , 2013 .

[3]  Bindeshwar Singh,et al.  Multilevel inverters: A literature survey on topologies and control strategies , 2012, 2012 2nd International Conference on Power, Control and Embedded Systems.

[4]  M. Forster,et al.  Reduction of DC bus capacitor ripple current with PAM/PWM converter , 2002, Conference Record of the 2002 IEEE Industry Applications Conference. 37th IAS Annual Meeting (Cat. No.02CH37344).

[5]  Yukihiko Sato,et al.  Analysis and minimization of ripple components of input current and voltage of PWM inverters , 1995 .

[6]  José R. Rodríguez,et al.  A Survey on Neutral-Point-Clamped Inverters , 2010, IEEE Transactions on Industrial Electronics.

[7]  S. El-Barbari,et al.  A Comprehensive Study of Neutral-Point Self-Balancing Effect in Neutral-Point-Clamped Three-Level Inverters , 2011, IEEE Transactions on Power Electronics.

[8]  G Narayanan,et al.  Harmonic Analysis of DC-Link Capacitor Current in Sinusoidally Modulated Neutral-Point-Clamped Inverter , 2013 .

[9]  T. Suzuki,et al.  Simple structure and control method for a neutral-point-clamped PWM inverter , 1993, Conference Record of the Power Conversion Conference - Yokohama 1993.

[10]  Suleiman M. Sharkh,et al.  Analysis of DC-Link capacitor losses in three-level neutral point clamped and cascaded H-Bridge voltage source inverters , 2010, 2010 IEEE International Symposium on Industrial Electronics.

[11]  G. Narayanan,et al.  Analytical Expression for RMS DC Link Capacitor Current in a Three-Level Inverter , 2011 .

[12]  Alireza Bakhshai,et al.  Control of three-phase voltage source inverter for renewable energy applications , 2011, 2011 IEEE 33rd International Telecommunications Energy Conference (INTELEC).

[13]  F. Renken,et al.  The DC-link capacitor current in pulsed single-phase H-bridge inverters , 2005, 2005 European Conference on Power Electronics and Applications.

[14]  G. Narayanan,et al.  Vector control of three-phase AC/DC front-end converter , 2008 .

[15]  Ui-Min Choi,et al.  New Modulation Strategy to Balance the Neutral-Point Voltage for Three-Level Neutral-Clamped Inverter Systems , 2014, IEEE Transactions on Energy Conversion.

[16]  Johann W. Kolar,et al.  Analytical calculation of the RMS current stress on the DC-link capacitor of voltage-PWM converter systems , 2006 .

[18]  Hirofumi Akagi,et al.  A New Neutral-Point-Clamped PWM Inverter , 1981, IEEE Transactions on Industry Applications.

[19]  G. Narayanan,et al.  Impact of dead-time on inverter input current, DC-link dynamics and light-load instability in rectifier-inverter-fed induction motor drives , 2016, 2016 International Symposium on Power Electronics, Electrical Drives, Automation and Motion (SPEEDAM).

[20]  Thomas A. Lipo,et al.  Reduction of DC bus capacitor ripple current with PAM/PWM converter , 2002 .

[21]  R. Cuzner,et al.  Three-level converter system , 2009, IEEE Industry Applications Magazine.

[22]  Folker Renken,et al.  Analytic Calculation of the DC-Link Capacitor Current for Pulsed Three-Phase Inverters , 2004 .