Research Of Digital Controlled 400Hz AC-AC Converter For Aerial Application

The design of 400Hz 3 phase digital controlled AC-AC converter is discussed. The content of the design work includes the hardware design of power module and control module, mathematical modeling and controller design, and DSP software programming. A prototype with rated power at 3kW is made to verified the design principles.The input module of the AC-AC converter is a 3 phase half bridge PWM rectifier. PWM rectifier can achieve unit power factor. But in 400Hz power system, there is high steady state error in the current loop of the rectifier due to switch frequency restriction. The controller design requirement of 400Hz 3-phase 4-wire high power factor rectifier is analyzed. A new control scheme employing orthogonal term generation method is proposed to achieve zero steady state error and independent control of each phase. The voltage balance of output capacitors is achieved by adding DC bias to PWM modulation wave. The validity of the theory is verified by experiment results.The output module of the AC-AC converter is a 3 phase half bridge inverter. Mosfet is used to achieve high switching frequency. The current loop and voltage loop control method is employed. The mathematical modeling and controller design of the inverter is discussed in detail in this paper.The DSP TMS320F28335 made by Texas Instruments is employed as the center control unit of both rectifier and inverter. Control calculation, AD conversion and software protection are implemented by DSP.A 3kW prototype is built and tested to verify the validity and feasibility of the design principles.