Small-Signal Model-Based Control Strategy for Balancing Individual DC Capacitor Voltages in Cascade Multilevel Inverter-Based STATCOM

This paper presents a new feedback control strategy for balancing individual DC capacitor voltages in a three-phase cascade multilevel inverter-based static synchronous compensator. The design of the control strategy is based on the detailed small-signal model. The key part of the proposed controller is a compensator to cancel the variation parts in the model. The controller can balance individual DC capacitor voltages when H-bridges run with different switching patterns and have parameter variations. It has two advantages: 1) the controller can work well in all operation modes (the capacitive mode, the inductive mode, and the standby mode) and 2) the impact of the individual DC voltage controller on the voltage quality is small. Simulation results and experimental results verify the performance of the controller.

[1]  Tiefu Zhao,et al.  ETO light multilevel inverter for STATCOM , 2008, 2008 34th Annual Conference of IEEE Industrial Electronics.

[2]  Laszlo Gyugyi,et al.  Dynamic compensation of AC transmission lines by solid-state synchronous voltage sources , 1994 .

[3]  Alex Q. Huang,et al.  Control Strategy Improving Fault Ride-Through Capability of Cascade Multilevel Inverter Based STATCOM , 2008, 2008 IEEE Industry Applications Society Annual Meeting.

[4]  Luis Marroyo,et al.  Individual Voltage Balancing Strategy for PWM Cascaded H-Bridge Converter-Based STATCOM , 2008, IEEE Transactions on Industrial Electronics.

[5]  Leon M. Tolbert,et al.  Multilevel converters for large electric drives , 1999 .

[6]  Alex Q. Huang,et al.  Real-Time Calculation of Switching Angles Minimizing THD for Multilevel Inverters With Step Modulation , 2009, IEEE Transactions on Industrial Electronics.

[7]  Zhong Du,et al.  An Optimal Combination Modulation Strategy for a Seven-level Cascade Multilevel Converter Based STATCOM , 2006, Conference Record of the 2006 IEEE Industry Applications Conference Forty-First IAS Annual Meeting.

[8]  Leopoldo García Franquelo,et al.  Modeling Strategy for Back-to-Back Three-Level Converters Applied to High-Power Wind Turbines , 2006, IEEE Transactions on Industrial Electronics.

[9]  J.A. Barrena,et al.  DC Voltage Balancing for PWM Cascaded H-Bridge Converter Based STATCOM , 2006, IECON 2006 - 32nd Annual Conference on IEEE Industrial Electronics.

[10]  F. L. Luo,et al.  Trinary hybrid multilevel inverter used in STATCOM with unbalanced voltages , 2005 .

[11]  R.W. De Doncker,et al.  A novel DC-link voltage control of PWM-switched cascade cell multi-level inverter applied to STATCOM , 2005, Fourtieth IAS Annual Meeting. Conference Record of the 2005 Industry Applications Conference, 2005..

[12]  Wenhua Liu,et al.  Multilevel Optimal Modulation and Dynamic Control Strategies for STATCOMs Using Cascaded Multilevel Inverters , 2007, IEEE Transactions on Power Delivery.

[13]  Bin Wu,et al.  Multilevel Voltage-Source-Converter Topologies for Industrial Medium-Voltage Drives , 2007, IEEE Transactions on Industrial Electronics.

[14]  Bin Chen,et al.  A Generalized Control Strategy of Per-Phase DC Voltage Balancing for Cascaded Multilevel Converter-based STATCOM , 2007, 2007 IEEE Power Electronics Specialists Conference.

[15]  Fang Zheng Peng,et al.  Multilevel inverters: a survey of topologies, controls, and applications , 2002, IEEE Trans. Ind. Electron..

[16]  Fang Zheng Peng,et al.  A multilevel voltage-source inverter with separate DC sources for static VAr generation , 1995, IAS '95. Conference Record of the 1995 IEEE Industry Applications Conference Thirtieth IAS Annual Meeting.

[17]  Wenhua Liu,et al.  DC voltage balancing technique using multi-pulse optimal PWM for cascade H-bridge inverters based STATCOM , 2004, 2004 IEEE 35th Annual Power Electronics Specialists Conference (IEEE Cat. No.04CH37551).

[18]  Cassiano Rech,et al.  Hybrid Multilevel Converters: Unified Analysis and Design Considerations , 2007, IEEE Transactions on Industrial Electronics.

[19]  H. Akagi,et al.  Control and Performance of a Transformerless Cascade PWM STATCOM With Star Configuration , 2007, IEEE Transactions on Industry Applications.

[20]  Leon M. Tolbert,et al.  Charge balance control schemes for cascade multilevel converter in hybrid electric vehicles , 2002, IEEE Trans. Ind. Electron..

[21]  S. Bhattacharya,et al.  Control strategy for cascade multilevel inverter based STATCOM with optimal combination modulation , 2008, 2008 IEEE Power Electronics Specialists Conference.

[22]  Alex Q. Huang,et al.  Real-Time Algorithm for Minimizing THD in Multilevel Inverters With Unequal or Varying Voltage Steps Under Staircase Modulation , 2009, IEEE Transactions on Industrial Electronics.