NCV-PWM Method for the Phase Current Reconstruction With DC Link Single Sensor

The DC link current sampling with a single sensor is a promising solution in the electric drive field due to its low cost and small volume. However, limited by the minimum sampling time, the current reconstruction unobservable area is the most intractable challenge in the traditional single sensor reconstruction method, especially in sector boundary areas, where the phase current cannot be reconstructed completely. In this article, a new non-zero compensation vector pulse width modulation (NCV-PWM) method is proposed to eliminate the current unobservable area. Firstly, by introducing the definition of minimum sampling time, the voltage space vector plane is accurately divided into different modulation areas. Then, by applying non-zero compensation vector in the sector boundary, the current sampling window is extended, and the sampling time requirement for the DC link current is satisfied. Finally, the practicability and accuracy of the NCV-PWM method are verified by experiments, and results show that the current reconstruction error is less than 2.86%, which provides accurate current feedback for high-performance motor control.

I. Introduction

Three phase AC motors are widely used in industry, transportation and other fields because of their high reliability, high power density, and high control accuracy [1], [2], [3], [4], [5], [6], [7]. In the AC motor drive system, phase current is the crucial parameter of vector control, and accurate current detection is of great significance in improving the performance of the control system. Generally, in order to realize closed-loop control, two or three current sensors are required to be installed on the AC output side of the inverter circuit to collect phase current information [8], [9], [10]. However, it will inevitably increase the volume of the driver, and the inconsistency between multiple sensors will also lead to sampling errors, which will affect the reconstruction accuracy seriously.