Research On Diode-Clamped High Voltage Transmitter Bridge

The demand for mineral resources is increasing with the rapid development of economy, and it is an effective way to solve the mineral resource crisis by the deep exploration. Controlled source audio frequence magnetotelluric(CSAMT) is an effective means for the deep exploration, which has advantages of deep exploration depth, high efficiency, high resolution, strong anti-interference ability and so on. The CSAMT instrument consists of a transmitter and a receiver, and the transmitter with a high voltage and high power level is good for enhancing magnetolelluric response signal strength, improving the signal to noise ratio of the receiver, and increasing the detection resolution of the instrument. Transmitter bridge serves as a key equipment of the transmitter system, and the high voltage transmitter bridge research to improve the power of the transmitter system is of great significance to solve the mineral resource crisis.This article researched the high power transmitter from devices and topologies, researched the current development situation of power electronics devices, analyzed the differences between inverters. The principle of multi-level inveters, which output sine wave, has been used to the application of geological exploration, and a new diode clamped high voltage transmitter bridge topology with appropriate control method has been proposed, achieving the purpose of high voltage and power by low voltage and low power devices, low cost and low power loss. The external IGBT is protected by clamped diode to avoid being broken down, without equalizing circuits. Since the function of clamped diodes, the bridge can output three-level step wave. Compared with two-level wave, it has low dv/dt and low EMI. The capacitance in DC side has been connected in parallel with separated power supply, so there is no capacitance equalizing problems, and the low voltage level power supply connected in series to output high power. Instead of outputting the traditional bipolar square wave, it outputs a approximate square wave with a voltage step. Compared with the traditional multilevel inverters, under the premise of the same input DC bus voltage, it has a smaller number of power devices, and the control method is simpler. The specific working process of bridge is in detail analyzed, and the feasibility of the design is verified by Simulink simulation. The overall structure of the transmitter bridge is designed, including a fault protection unit, an IGBT drive control unit, a digital controller, and a high voltage isolation auxiliary power supply. The main circuit design scheme of the high voltage transmitter bridge has been researched, and the power loss calculation and the design of the air cooling heat dissipation has been completed. The experimental prototype was designed and manufactured, and a field simulation experiment has been conducted in laboratory environment. The actual emission voltage reached 1200 V and current reached 20 A, with a high quality of three level wave and low dv/dt. The experimental results show that the transmitter bridge has the characteristics of high power, low voltage devices used, low electromagnetic interference, high reliability and so on.