| 摘要 |
<P>PROBLEM TO BE SOLVED: To ensure that an electric power conversion apparatus is operated continuously with high reliability even when a system voltage VA dips momentarily or when it is up again, the apparatus having an inverter unit 10 composed by connecting the AC sides of a main inverter 5 and a sub-inverter 7 with a relatively low DC voltage in series to make electric power from a distributed power supply 1 linked to an electric power system 15. <P>SOLUTION: When a system voltage VA is normal, a main inverter 5 outputs a one-pulse voltage in a half cycle matched to the system cycle, while a sub-inverter 7 exerts PWM control, to control an inverter current i, whereby a voltage Vs of a sub-capacitor 8 of the sub-inverter 7 is made to follow a directive value. When a momentary dip occurs, the control mode of the inverter unit 10 is switched over, letting the sub-capacitor 8 of the sub-inverter 7 be bypassed, and a DC voltage Vm of the main inverter 5 is raised above a maximum voltage value Vp at normal time of the system voltage VA, in which way the main inverter 5 is PWM controlled. Therefore, even when the system voltage VA dips momentarily or when it is up again, operation is continued by controlling the inverter current i. <P>COPYRIGHT: (C)2013,JPO&INPIT |
