Fully integrated multi-phase grid-tie inverter
In a grid-tie inverter, the DC input is phase and pulse-width modulated to define multiple phase shifted voltage pulses with the width of each pulse being modulated according to the grid AC amplitude for the corresponding portion of the AC phase.
1. A method of synchronizing a DC input signal to an AC signal, comprising
phase-and-amplitude modulating the DC signal to define multiple phase-shifted high frequency signal pulses that each define a portion of an AC voltage envelope that has a frequency corresponding to the frequency of the AC signal, and
combining the multiple high frequency signals to define an AC output signal.
2. A method of claim 1 , wherein the multiple phase-shifted high frequency signals are formed by feeding the DC signal through an array of switching transistors and sequentially switching the switching transistors.
3. A method of claim 2 , wherein the sequence of switching the switching transistors is controlled to provide a voltage pulse from each transistor that is phase shifted relative to the other transistors and has a pulse width to define a portion of the AC voltage envelope.
4. A method of claim 3 , wherein the phase of each switching transistor pulse corresponds to a phase of the AC voltage envelope, and the pulse width of each switching transistor is related to the amplitude of the AC voltage envelope for the corresponding phase.
5. A method of claim 4 , wherein the grid phase and the pulse phase of each coil element in the coil array is monitored using an on-chip ferro-magnetically isolated current sensor (flux gate).
6. A method of claim 1 , wherein the AC signal has a frequency corresponding to a grid frequency.
7. A method of claim 1 , further comprising performing the synchronizing of the DC input signal to the mains AC signal using only integrated structures.
8. A grid-tie inverter for synchronizing a DC input signal to a grid AC signal, comprising
an array of switching transistors connected to the DC input, and
a controller for controlling the control electrodes of the switching transistors to define voltage pulses that are phase shifted relative to each other the pulse-widths being modulated according to the grid AC signal amplitude.
9. A grid-tie inverter of claim 8 , further comprising a ferro-magnetically isolated current sensor (flux gate) to monitor the phase of the grid AC and the pulse phases.
10. A grid-tie inverter of claim 8 , wherein the AC signals have a frequency that is 100,000 to 1000,000 times as high as the mains AC frequency.
11. A grid-tie inverter of claim 8 , wherein the grid tie inverter is integrated on one or more chips.