Patent ID: 9685884
Date: 2017-06-20
CPC Classifications: H02M,H02P

Claim:
1. In a seven-level inverter apparatus comprising: a three-phase three-level inverter which converts a DC of a first DC power source of three levels into an AC; three single-phase five-level inverters, each of which converts a DC of a second power source of three levels having the same voltage as the first DC power source into an AC, an output thereof being connected in series with an output of each phase of the three-phase three-level inverter; and pulse width modulation control means provided for each phase which performs pulse width modulation control of a give voltage reference to supply gate pulses to switching devices composing the relevant phase of the three-level inverter and the single-phase five-level inverter of the relevant phase; the seven-level inverter apparatus is characterized in that: the pulse width modulation control means has means which converts the voltage reference into a pulse width modulated voltage level of the relevant phase, and state transition means which determines an output of a switching leg of the relevant phase of the three-level inverter, and outputs of outside and inside switching legs of the single-phase five-level inverter, based on transition of this voltage level; and the state transition means makes all of the three outputs of the switching leg of the relevant phase of the three-level inverter, and the outside and inside switching legs of the single-phase five-level inverter 0 or positive, when the voltage level is positive, makes all of the three outputs of the switching leg of the relevant phase of the three-level inverter, and the outside and inside switching legs of the single-phase five-level inverter 0 or negative, when the voltage level is negative, and makes all of the three outputs of the switching leg of the relevant phase of the three-level inverter, and the outside and inside switching legs of the single-phase five-level inverter 0, when the voltage level is 0.