Multiple inverter system

A multiple inverter system comprising:

• at least one input transformer having a plurality of three-phase secondary windings;
• at least one three-phase inverter;
• and
• a plurality of single-phase inverter cells,
• said single-phase inverter cells being connected in series for a plurality of stages (n−1) to compose multiple phases and connected to each of the same phases of said three-phase inverters to supply electric power to a multiple phase load.

A multiple inverter system, comprising:

• a plurality of input transformers having secondary windings;
• and
• a plurality of unit inverter cells connected in series for n-stages (where n≧3) to compose multiple phases, supplies electric power to a multiple phase load in combination with said input transformers, said plurality of unit inverter cells being connected to said secondary windings,
• wherein said input transformers are provided with 3n sets of three-phase windings at the secondary side, and
• wherein secondary windings of said transformers are connected to a stage of said plurality of unit inverter cells in which each secondary winding of a stage is out of phase with the other secondary windings of said stage.

A multiple inverter system, comprising;

• a rectifier to convert AC power into DC power;
• a group of inverters, which are to convert DC power of said rectifier into AC power, provided with a plurality of voltage source unit inverters composing a plurality of bridge connected semiconductor devices, the input sides of said unit inverters connected to said rectifier in parallel via smoothing capacitors, respectively, output sides of said unit inverters connected in series and also connected to an AC load;
• a fuse serially connected between said rectifier and said unit inverter;
• a bypass switch provided between said rectifier and unit inverter and connected in parallel with said unit inverter and forms a circuit to circulate load current when said circuit is electrically closed;
• a unit inverter control means for giving a firing command to semiconductor devices composing said unit inverter in the specified order;
• an abnormal operation detecting means for detecting said abnormal operating state of said unit inverter based on said AC output of said unit inverters;
• a DC abnormality detecting means for detecting an abnormality of DC input of said unit inverter;
• and
• a bypass switch control means for melting said fuse on applicable to said unit inverter by giving a circuit closing command to said bypass switch corresponding to an applicable unit inverter when both of said abnormal operation detecting means and abnormal DC detecting means detect said abnormality.

A multiple inverter system comprising:

• a rectifier to convert AC power to DC power;
• a group of inverters, which are to convert DC power of said rectifier into AC power, provided with a plurality of voltage source unit inverters composing a plurality of bridge connected semiconductor devices, the input sides of which are connected in parallel with said rectifier via a smoothing capacitor and the output sides of which are connected in series and connected to an AC load;
• fuses serially connected between said rectifiers and unit inverters;
• bypass switches provided between said rectifiers and said unit inverters, connected in parallel with said unit inverters and form a circuit to circulate load current when said circuit is electrically closed;
• a pulse width modulation unit inverter control means for giving a firing command in the specified order to semiconductor devices composing said unit inverters;
• an abnormality judging means for making the judgment of troubles related to said unit inverter control means;
• and
• a bypass switch control means for melting said fuse by giving a circuit closing command to said bypass switch of applicable unit inverter when said abnormality judging means judges said abnormality.

A multiple inverter system, comprising:

• a rectifier to convert AC power to DC power;
• a group of inverters, which are to convert DC power of said rectifier into AC power, provided with a plurality of voltage inverters composing a plurality of bridge connected semiconductor devices, the input sides of which are connected in parallel with said rectifier via a smoothing capacitor, the output sides of which are serially connected and to an AC load;
• a fuse serially connected between said rectifier and said unit inverter;
• bypass switches provided between said rectifiers and said unit inverters, connected in parallel with said unit inverters and form, a circuit to circulate load current when said circuit is electrically closed;
• a pulse width modulation unit inverter control means for giving a firing command in the specified order to semiconductor devices comprising said unit inverters;
• an operation abnormality detecting means for detecting an abnormal operating state of said unit inverters based on said AC output of said unit inverters;
• a DC abnormality detecting means for detecting abnormality of DC input of said unit inverters;
• and
• a bypass switch control means for melting said fuse by giving a circuit closing command to said bypass switch of applicable unit inverter when both of said operation abnormality detecting means and DC abnormality detecting means detect abnormality;
• said system is operated by increasing the percentage modulation of said unit inverter in the phase caused abnormality out of said inverter group to more than one time by said unit inverter control means.

A multiple inverter system, comprising:

• a rectifier to convert AC power into DC power;
• a group of inverters, which are to convert DC power of said rectifier into AC power, provided with a plurality of voltage unit inverters composing a plurality of bridge connected semiconductor devices, the input sides of said unit inverters are connected to said rectifier in parallel with it via smoothing capacitors, and the output sides of which are serially connected and to an AC load;
• a fuse serially connected between said rectifier and said unit inverter;
• bypass switches provided between said rectifiers and said unit inverters, connected in parallel with said unit inverters and form a circuit to circulate load current when said circuit is electrically closed;
• a pulse width modulation unit inverter control means for giving a firing command in the specified order to semiconductor devices composing said unit inverters;
• an operation abnormality detecting means for detecting an abnormal operating state of said unit inverters based on said AC output of said unit inverters;
• a DC abnormality detecting means for detecting abnormality of DC input of said unit inverters;
• and
• a bypass switch control means for melting said fuse by giving a circuit closing command to said bypass switch of applicable unit inverter when both of said operation abnormality detecting means and DC abnormality detecting means detect abnormality;
• a group of healthy phase inverters are operated by adapting to the number of inverters in the phase detected by said operation abnormality detecting means.