Fine Three-Phase Current Reconstruction based on Calculating the Phase-Shifted Voltage Reference Using Only the DC Current Sensor of an Inverter and Its Application to a PM Motor Drive

摘要

This paper proposes a new current reconstruction method that uses a DC-link current sensor for an inverter. In a typical current reconstruction method, an error of the average motor current is likely to occur because there are only two reconstruction points in one carrier period. In addition, the phase current harmonics increases because the carrier wave and voltage references are changed in a region where current reconstruction is difficult. This paper proposes three methods for current reconstruction. The first method calculates the average motor current more accurately by oversampling. The oversampling is synchronized to pulse-width modulation (PWM) switching and is conducted by combining the conventional method and the second method. The second method realizes the difference detection by using the resistance-capacitance (RC) circuit. The third method calculates the current in the region where current reconstruction is difficult by calculating the phase-shifted voltage references. The current calculation method does not increase the current harmonics in this region because it does not change the carrier wave and voltage references. The effectiveness of these methods and the motor control with the reconstructed current were confirmed in experiments.