As a typical power electronics topology, the three-phase bridge inverter circuit is widely used in motor driver, new energy grid-connected inverter, and other power electronic equipment. Current is an important parameter for the control and protection of inverter, how to obtain current information stably and accurately is the key to realize high-performance control of inverter. However, traditional control often overlooks fundamental, complex, and extensible problems caused by current parameters. Over recent years, many problems have been raised around the reliability of current detection and the improvement of accuracy, but most of the problems lack a closed-loop review of problem development. Aiming at these problems, this paper summarizes the related problems of current detection in three-phase bridge inverter, hoping to inspire follow-up research. First of all, based on the principle analysis, the current sensors that are most widely used are summarized based on operating principle, sampling accuracy, advantages and disadvantages, including Hall current sensors, fluxgate current sensors, and shunts. Different current detection circuits are directly determined from the analysis of sensor installation characteristics and the number of uses, which are mainly divided into multi-sensor detection circuits and single-sensor detection circuits, and specifically including current sensing at the high-side (AC output side) of the load using two or three current sensors; current sensing on the low side using two or three current sensors; current sensing on the DC bus using a single current sensor; multi-position coupling for current sensing using a single Hall/fluxgate current sensor detection (intermediate bridge arm coupling (IBAC), upper-lower bridge arm coupling (ULBAC), and multi-position coupling (MPC)). This paper summarizes and analyzes the different current information, advantages, and disadvantages contained in the detection circuits at different positions. However, in actual use, reliable and high-precision current sampling is caused by a combination of direct and indirect reasons. The direct reason includes long-term use of the point current sensor, or inaccurate measurement accuracy under harsh conditions. In the comprehensive use of the inverter, under different control algorithm strategies, the source (inherent error) of the current detection error occurs, so the research branch of the indirect cause of improving the current quality through PWM control strategy adjustment is derived. This paper summarizes and analyzes the influence of different control strategies such as the PWM waveform adjustment method, voltage vector synthesis method, and state observation method on the current in the case of a single current sensor, as well as the comparison of advantages and disadvantages. Finally, this paper comprehensively analyzes the direct and indirect causes of current detection. There are two types of errors in the current sampling process: one is an inherent error due to PWM; the other is sensor sampling error due to factors such as temperature or aging. Both errors are directly introduced into the measured current without correction. The inherent errors caused by PWM are divided into time-sharing errors, non-homogenous errors, and switching errors. The sampling path is composed of a Hall sensor, a conversion circuit, a filter circuit, and an analog-to-digital (A-D) conversion circuit. Affected by device tolerance, temperature drift, aging, noise, etc., drift errors and gain errors will occur in the current sampling path. The two kinds of errors can be corrected by each other, and the suppression and compensation of sampling errors through control strategies is the current mainstream research branch of mutual errors. In the future, there will still be major challenges in current detection: with the high frequency of power electronics, the research of current sensors with high bandwidth and high response speed is still an important branch; in the face of single current sensor sampling, the current sampling that is affected by multiple factors such as the optimization of the PWM strategy and the signal processing process should be considered comprehensively; for the research on the improvement of current accuracy, attention should be paid to the closed-loop relationship between the sensor itself and the control strategy, and at the same time, new background factors such as electromagnetic interference should be introduced from the foundation to improve the current detection accuracy. © 2023 Chinese Machine Press. All rights reserved.
