Capacitors voltage balancing in half bridge inverter for low switching frequency applications

This paper analyzes the two commonly used current control methods for high power, low switching frequency applications involving half bridge inverter. First, the problem of voltage balancing of two DC link capacitors in the half bridge inverter has been discussed. The two current control methods used for the comparison are hysteresis current control and ramp comparison current control methods. It is shown that the hysteresis current controller leads to the situation of unbalancing of the DC link voltages at low switching frequency operation of the switches. This problem can be eliminated when the switches of the inverter are operated at fixed switching frequency using ramp comparison control method and it is shown that this current control method has self balancing capability. The results are verified using PSCAD/EMTDC simulation results and validated through an experimental model using FPGA based controller.