Control of parallel inverters based on CAN bus in large-capacity motor drives

Parallel connection of inverters or converters is one useful method for solving the high power requirements. It has also been used to reduce harmonics and reduce pulse width modulation (PWM) switching frequency. The parallel structure of two voltage inverters sharing a single standard three-phase machine is analyzed in the paper. In AC variable-speed drive systems, parallel inverters work under variable-voltage- variable-frequency (VWF) conditions. The problems of synchronization and load sharing must be solved. In order to tackle the problems, a master-slave parallel control three-phase inverter system prototype based on CAN bus is constructed. Firstly, the speed regulator of the main inverter controller generates the reference current of each inverter. By the respective current regulator, the slave inverters will follow the reference current without static error. Secondly, the communication among the parallel inverters is achieved by CAN bus, with less mutual wires. The simulation results confirm the feasibility of the proposed control algorithm and show the motor current can be shared and has good dynamic characteristics, being superior to single module.