Improved DC Offset Error Compensation Algorithm in Phase Locked Loop System

Abstract

-This paper proposes a dc error compensation algorithm using dq-synchronous coordinate transform digital phase-locked-loop in single-phase grid-connected converters. The dc errors are caused by analog to digital conversion and grid voltage during measurement. If the dc offset error is included in the phase-locked-loop system, it can cause distortion in the grid angle estimation with phase-locked-loop. Accordingly, recent study has dealt with the integral technique using the synchronous reference frame phase-locked-loop method. However, dynamic response is slow because it requires to monitor one period of grid voltage. In this paper, the dc offset error compensation algorithm of the improved response characteristic is proposed by using the synchronous reference frame phase-locked-loop. The simulation and the experimental results are presented to demonstrate the effectiveness of the proposed dc offset error compensation algorithm.

A Back-EMF Estimation Error Compensation Method for Accurate Rotor Position Estimation of Surface Mounted Permanent Magnet Synchronous Motors

“…Equation (12) is converted into the synchronous coordinate system using Equation (6), and it can be calculated as Equation (13). The d-axis voltage of Equation (12) …”

“…Typically, the measured back-EMF is digitalized through matching circuits including voltage sensor, low pass filter, and A/D converter. As a result, a DC offset error may be generated from the voltage sensor itself because of sensor errors, the thermal variation of the analog electric device and the quantization error of the A/D converter [11][12][13][14]. Figure 4 represents the error factors in the voltage measurement path.…”

“…When using the sensorless control method based on the back-EMF estimation, the back-EMF information is measured by the voltage sensor of the system after passing the digital controller signal through a low pass filter (LPF) and analog to digital conversion (ADC). In this process, back-EMF measurement errors can occur due to the nonlinearity of the voltage sensor, the thermal variation of the analog electric device, and ADC quantization errors [11][12][13][14]. At this time, the main component of any occurring nonlinear errors is the direct current (DC) offset error, and when this DC offset error component occurs, it causes a pulsation in the synchronous coordinate system d axis voltage.…”