Digital Implementation of Carrier Displaced Simplified Space Vector PWM for CMV Reduction

Abstract

The switching action of two level voltage source inverter naturally generates common-mode voltage. Common mode voltage (CMV) is a known culprit for reducing induction motor drive life expectance and aforetime unprecedented failure. In literature, CMV mitigation techniques adopted as remedy necessitate use of either multilevel inverters or additional passive components like common mode filters. Moreover, numerous motor drives available with the industries rely on two level inverters. To avoid extra hardware components, carrier displaced sine PWM technique is adopted. Although it minimizes CM voltage, the DC link utilization remains lower. Therefore, this work proposes a method to minimize CM voltage and exploit DC link effectively without any hardware changes into the existing drive. In the proposed work, carrier displaced simplified Space Vector Modulation (SVM) algorithm is presented for CM voltage reduction in two level VSI. SVM inherently enhances DC bus utilization and the overall CMV further reduces due to minimal DC bus voltage requirement. The presented carrier displaced SVM algorithm is rudimentary in approach and does not mandate use of high performance DSP or FPGA digital controller. In turn, no additional cost is incurred neither for extra hardware nor an expensive processor. The algorithm may be applied for motor-drives within existing digital controller platform with only elementary firmware changes. Simulation and experimental results validate feasibility of presented work for induction motor drive applications.