Single-loop Current Sensorless Control with Self-detection of Conduction Losses Applied to Neutral Point Clamped Multilevel Converter

Current sensor is usually considered a compulsory part in current controlled power electronic converters. This paper presents a single-loop current sensorless control method for neutral point clamped multilevel converter. In order to control the current shape, the proposed method does not use feedback from current sensor and contains only a single control loop with voltage feedback to stabilize the DC bus voltage. The current control is implemented by means of precise calculation of volt-second balance of the inductor with consideration of conduction losses. Considering that values of parasitic components may change during converter's operation, a novel mathematical observer is presented to implement continuous monitoring of parasitic elements introduced by switching components and resistance of the inductor. Moreover estimation of inductance is proposed with a simple method.