Analysis of parallel operation methods of PWM inverter sets for an ultra-high speed elevator

Characteristics of some current control schemes that are for an inverter parallel set operation and easily implemented by microprocessor, are analyzed. To analyze an inverter parallel set system, equivalent circuits separated into two groups are derived. One group generates a motor current, the other generates a cross current flowing between inverters, and they are decoupling approximately. Thus, these circuits are utilized to comprehend the behavior of an inverter parallel set system. Applying these circuits, three current control schemes based on a suboscillation current control are analyzed and a control scheme, which can regulate both the motor current and the cross current, shows excellent performance.