초록 ▼

Multi-phase power is provided to a load via the use of an inverter which has an even number of inverter legs. DC source voltage, such as from an AC-to-DC converter receiving power from a main AC power supply or from an independent DC power source such as a battery, is provided to the inverter. The D

Multi-phase power is provided to a load via the use of an inverter which has an even number of inverter legs. DC source voltage, such as from an AC-to-DC converter receiving power from a main AC power supply or from an independent DC power source such as a battery, is provided to the inverter. The DC source voltage is provided on DC bus lines of the inverter so as to be symmetric about ground. Switching devices in the inverter legs are controlled using a modulation strategy to synthesize desired output voltage waveforms on the inverter leg outputs from the voltage on the DC bus lines. The modulation strategy is subject to a modulation constraint such that, at any one time, half of the inverter legs provide a positive output voltage signal with respect to ground, and the other half of the inverter legs provide a negative output voltage signal, of equal magnitude, with respect to ground. If the multi-phase load to which the inverter is connected is a balanced impedance, the present invention makes possible the reduction or elimination of common mode voltage and, therefore, common mode current. Load balancing may be achieved using a multi-phase second order filter connected between the inverter leg outputs and the load. The present invention may be applied to power conversion systems including hard switching or soft switching inverters, and may be used in combination with conventional inverter modulation strategies.

대표청구항 ▼

[ What is claimed is:] [1.] A multi-phase power conversion system for reducing common mode voltage, comprising:(a) a DC-to-AC power inverter having an even number of at least four inverter legs connected between positive and negative DC bus lines, wherein each inverter leg includes inverter switchin

[ What is claimed is:] [1.] A multi-phase power conversion system for reducing common mode voltage, comprising:(a) a DC-to-AC power inverter having an even number of at least four inverter legs connected between positive and negative DC bus lines, wherein each inverter leg includes inverter switching devices responsive to switching device control signals to connect the positive or negative DC bus lines to an inverter leg output;(b) means for symmetrizing a DC source voltage provided to the positive and negative DC bus lines such that the DC source voltages applied to the positive and negative DC bus lines are symmetric about ground; and(c) switching device controller means for providing the switching device control signals to the inverter switching devices in the inverter legs to switch the inverter switching devices in a pattern which implements a modulation strategy such that a multi-phase AC voltage waveform is synthesized on at least three of the inverter leg outputs, and wherein the modulation strategy is subject to a modulation constraint such that at all times an equal number of the inverter leg outputs are connected to the positive DC bus line by the inverter switching devices as are connected to the negative DC bus line by the inverter switching devices.