Modeling and analysis of digital steady current circuit of transmitter for borehole-ground electrical potential measurement system

This article, based on the main circuit structure of full-bridge DC/DC converter in the transmitter of the borehole-ground electrical potential measurement system, presents the structure of single-closed-loop current feedback control system with voltage mode control for output current stabilization. According to the average state space method, the state space equation of the main circuit with steady output current of transmitter was established, the AC small-signal model of the main circuit was acquired and the open-loop transfer function was then deduced as a result. The method of design and specific parameters of the PI compensation network were provided and the open-loop transfer function of the system was deduced. The incremental PI control algorithm was adopted and the digital control was realised by TMS320F2812 DSP system programming. MATLAB was used to analyze the system for its open-loop frequency characteristics and its closed-loop dynamic characteristics, the result of which shows the correctness of the modelling approach.