Statistical Approach to Robust Design of Control Schemes for Series or Parallel Connected Power Devices

Abstract

High power, high speed operation of circuits requires that devices such as IGBTs and MOSFETs be connected in series and/or parallel. Such systems are being increasingly used in high power drives, traction, active power filters and other high power industrial applications. But no matter how perfect the design and fabrication may be, no two devices can be identical, resulting in some level of incompatibility in such systems. Therefore, there is a reduction in the overall reliability unless, care is taken to optimize the parameters of their control schemes which govern the operation of such systems. This paper reports a reliability enhancement scheme for such systems. Example of series connected IGBTs using a current feedback active gate control scheme has been considered in conjunction with the Taguchi method for this purpose. The complete strategy and calculations involved are presented, as are the experimental results to validate theoretical predictions. Results show a significant improvement in performance when the control scheme parameters are optimized using the Taguchi method. A similar approach may be followed for parallel connected devices (e.g. MOSFETs connected in parallel).