DC content control for an inverter
AssigneeSundstrand Corporation
InventorsDerrick I. Roe, Christopher J. Rozman, Bradley J. Recker
Life of this patent
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Abstract
Power inverters for converting DC power into AC power often produce a DC component in the inverter output which is objectionable. In order to overcome this problem, an inverter control according to the present invention detects the magnitude of the DC component in the inverter AC output power and adjusts the time of selected rising and falling edges of control waveforms for switches in the inverter to reduce the magnitude of the DC component.
Claims7
A control for an inverter having a switch which is operated in accordance with a waveform having spaced rising and falling edges, comprising:
- means for detecting the magnitude of a DC component in the inverter AC output power;
- and
- means responsive to the detecting means for adjusting the time of selected rising or falling edges to reduce the magnitude of the DC component.
A control for a pulse width modulated (PWM) inverter which develops N passes outputs each produced by a pair of switches which are alternately operated in accordance with a PWM waveform stored in a memory and having rising and falling edges comprising:
- a control signal generator for each phase output including a low pass filter coupled to the phase output which develops a signal representing the magnitude and polarity of a DC component in the phase output;
- an edge select circuit coupled to the low pass filter for selecting edges of the PWM waveform to be delayed in dependence upon the polarity of the DC component;
- and
- an edge delay circuit coupled to the memory, the low pass filter and the edge select circuit for delaying the selected edges of the PWM waveform by amounts which depend upon the magnitude of the DC component in the phase output to produce a control signal for controlling the switches.
Dependencies are inferred from the claim text.