Single-phase voltage source inverter circuit with power decoupling, and control methods
A single-phase voltage source inverter including a first stage configured to be connectable to a DC source, and a second stage configured to be connectable to an AC load, the first stage including a bridge leg including first and second decoupling switches, the bridge leg connected through an inductor to a decoupling capacitor, where the decoupling capacitor is in series with the DC source when the inverter is connected to the DC source, and the second stage including a bi-directional H-bridge inverter including first, second, third and fourth switches. The decoupling capacitor can be a small film capacitor. The first and second decoupling switches are the only decoupling switches in the bridge leg. The first controller can use pulse width modulation and the second controller uses sinusoidal pulse width modulation. The first controller can use pulse width modulation and the second controller uses pulse energy modulation.
1. A single-phase voltage source inverter comprising:
a first stage adapted to be connected to a DC source, wherein the DC source provides an input DC current and a second stage adapted to be connected to an AC load, whereby the AC load includes a second-order ripple power as produced by an AC voltage and an AC current,
the first stage comprising a bridge leg comprising first and second current-bidirectional decoupling switches, the bridge leg connected through an inductor connected between the decoupling switches to a small film decoupling capacitor, where the decoupling capacitor is in series with the DC source when the inverter is connected to the DC source, whereby current can flow into and out of the decoupling capacitor bi-directionally,
the second stage comprising a bi-directional inverter comprising first, second, third and fourth switches,
a first controller for modulating the first stage to provide power decoupling functionality comprising diverting the second-order ripple power into the small film decoupling capacitor, whereby the second-order ripple is removed from the input DC current,
and a second controller for modulating the second stage.
2. The single-phase voltage source inverter of claim 1 , wherein the first and second decoupling switches are the only decoupling switches in the bridge leg.
3. The single-phase voltage source inverter of claim 1 , wherein the bi-directional inverter is an H-bridge.
4. The single-phase voltage source inverter of claim 1 , wherein the first controller uses pulse width modulation and the second controller uses sinusoidal pulse width modulation.
5. The single-phase voltage source inverter of claim 1 , wherein the first controller uses sinusoidal pulse width modulation and the second controller uses pulse energy modulation.
6. The single-phase voltage source inverter of claim 1 , wherein the AC load is an AC grid.
7. The single-phase voltage source inverter of claim 1 , wherein the small film capacitor has a capacitance measured in micro Farads.
8. The single-phase voltage source inverter of claim 1 , wherein the small film capacitor has a capacitance of 160 micro Farads.
9. The single-phase voltage source inverter of claim 1 , wherein modulating the first stage to provide power decoupling functionality in the first stage further comprises:
controlling voltage across the decoupling capacitor as a DC-biased sine wave, adding a DC component of the voltage across the decoupling capacitor with input DC voltage from the DC source thereby providing voltage-boosting functionality, and
cancelling out the second-order ripple power using an AC component of the voltage across the decoupling capacitor.