Research On Current-type DC-AC Conversion System For Low Input Voltage Motor Driv

With the development of new energy technology and the promotion of electric energy substitution technology in China,the electric motors are widely used in electric tools such as battery trucks and lawn mowers.The current motor drive system based on voltage source inverter has problems such as high output common mode current,poor stator voltage waveform,and can only operate in buck mode.At the same time,motor drive system powered by batteries typically require low input voltage and wide speed range.Therefore,it is of great significance to research on motor drive system with wide output voltage range,small common mode current,and high output waveform quality.A current source DC-AC converter system for low input voltage motor drive is proposed based on a comprehensive discussion of the development and application status of motor drive converters.And intensive research was conducted on the circuit topology,steady-state principle,high-frequency switching process,space vector modulation strategy,and key circuit parameter design of the proposed converter.Based on this,simulation and experimental research on this type of converter system has been completed,with the specific research content as follows:1.The circuit topology of the current source DC-AC conversion system for low input voltage motor drives has been proposed.The topology consists of an input power supply,a high-gain boost-buck chopper circuit with an active clamp branch with ZVS,an m-phase current source inverter circuit,an output filter circuit,and a permanent magnet synchronous motor load.The clamp branch is connected in parallel with an energy storage switch to achieve voltage clamping of the energy storage switch and zero voltage switching control.The currentcontrolled DC-AC conversion system has the advantages of single-stage power conversion,wide output voltage range,high efficiency,and high reliability.2.A space vector modulation strategy applicable to the circuit topology of current source DC-AC converter system has been proposed.The modulation strategy designed based on the different energy storage/release modes of coupled inductors within a high-frequency switching period achieves ZVS control of the energy storage switch.Three stage modulation,four stage modulation,and step-down operation modulation have been designed.And a closed loop control strategy for speed and current was designed.3.A detailed analysis was conducted on the high-frequency steady-state switching process of the current source DC-AC converter system.Based on the analysis of the high-frequency steady-state switching process,the waveform of key circuit parameters,circuit parameter design,voltage transmission relationship during steady-state process,and the implementation of softswitching parameter constraint relationships were studied.4.The simulation system is built with PSIM software according to the proposed circuit topology,space vector modulation strategy and key circuit parameter design.At the same time,an experimental prototype of 1k W 24VDC/84 VAC current mode DC-AC converter system is designed and manufactured.The simulation and experimental results verify the feasibility and advancement of the proposed current mode DC-AC converter system.