Current sensing system for full-bridge pulse-width modulated inverter system

1. An inverter system comprising:

an input having an input current, a positive DC node, and a negative DC node adapted to be coupled to a DC power source and to receive input DC power from the DC power source;

an output, having an output current, adapted to be coupled to at least one load and to provide output AC power to the at least one load;

a first inverter leg including a first switching device and a second switching device;

a second inverter leg including a third switching device and a fourth switching device, the first inverter leg and the second inverter leg being coupled between the input and the output and adapted to convert the input DC power to the output AC power;

a single current sensor coupled to one of the negative DC node and the positive DC node;

a controller assembly adapted to measure a current through the single current sensor and determine an inductor current through an inductor coupled between the second inverter leg and the output based at least in part on the current through the single current sensor, determine the input current based at least in part on the current through the single current sensor, and determine the output current based at least in part on the current through the single current sensor; and

an output capacitor coupled across the output;

wherein the controller assembly is further adapted to:

estimate a voltage across the output capacitor based at least in part on a model of the output capacitor;

compare the estimated voltage across the output capacitor and an output voltage to determine a current through the output capacitor; and

compare the current through the output capacitor and the inductor current to determine the output current.

2. The inverter system of claim 1 , wherein the single current sensor is a non-inductive current sense resistor.

3. The inverter system of claim 2 , further comprising a first capacitor coupled between the negative DC node and the positive DC node, and a second capacitor coupled between the negative DC node and the positive DC node, and wherein the non-inductive current sense resistor is coupled between the first capacitor and the second capacitor.

4. The inverter system of claim 3 , further comprising a first voltage sensor positioned to measure an input voltage, and a second voltage sensor positioned to measure the output voltage, wherein the controller assembly is adapted to determine a value for the input current based on the current through the single current sensor and the input voltage, and adapted to control the first inverter leg and the second inverter leg based on the value for the input current and the output current.

5. The inverter system of claim 4 , wherein the controller assembly is adapted to:

estimate a voltage across the first capacitor based at least in part on a model of the first capacitor;

compare the estimated voltage across the first capacitor and the input voltage to determine a current through the first capacitor; and

compare the current through the first capacitor and the current through the single current sensor to determine the input current.

6. The inverter system of claim 2 , wherein the controller assembly is adapted to control the first inverter leg and the second inverter leg based on a switching signal having a triangular waveform, and sample the current through the single current sensor at a valley of the switching signal during a positive cycle of an output voltage to determine the inductor current.

7. The inverter system of claim 6 , wherein the controller assembly is adapted to sample the current through the single current sensor at a peak of the switching signal during a negative cycle of the output voltage to determine the inductor current.

8. The inverter system of claim 1 , further comprising an overcurrent protection system adapted to determine the occurrence of an overcurrent condition and control a position of the third switching device and fourth switching device of the second inverter leg during the overcurrent condition.

9. A method for operating an inverter system including an input having an input current, a positive DC node, and a negative DC node, an output, having an output current, coupled to at least one load, a first inverter leg and a second inverter leg coupled between the input and the output, an inductor coupled between the second inverter leg and the output, and a single current sensor coupled to one of the negative DC node and the positive DC node, the method comprising:

receiving DC power from a DC power source at the input;

measuring a current through the single current sensor coupled to one of the negative DC node and positive DC node; and

determining an inductor current at the inductor based at least in part on the current through the single current sensor, the input current based at least in part on the current through the single current sensor, and the output current based at least in part on the current through the single current sensor;

wherein the inverter system includes an output capacitor coupled across the output, and wherein determining the output current further includes:

measuring an output voltage;

determining a voltage across the output capacitor based at least in part on a model of the output capacitor;

comparing the estimated voltage across the output capacitor and the output voltage to determine a current through the output capacitor; and

comparing the current through the output capacitor and the inductor current to determine a value for the output current.

10. The method of claim 9 , wherein the single current sensor is a non-inductive current sense resistor, and wherein measuring the current through the single current sensor includes measuring a voltage drop across the non-inductive current sense resistor.

11. The method of claim 10 , wherein determining the inductor current includes sampling the current through the single current sensor at a valley of a switching signal during a positive cycle of an output voltage, wherein the first inverter leg and second inverter leg are controlled based on a switching signal having a triangular waveform.

12. The method of claim 11 , wherein determining the inductor current includes sampling the current through the single current sensor at a peak of the switching signal during a negative cycle of the output voltage.

13. The method of claim 12 , wherein the inverter system includes a first capacitor coupled between the negative DC node and the positive DC node, and wherein determining the input current includes:

measuring an input voltage;

determining a voltage across the first capacitor based at least in part on a model of the first capacitor;

comparing the estimated voltage across the first capacitor and the input voltage to determine a current through the first capacitor; and

comparing the current through the first capacitor and the DC node current to determine a value for the input current.

14. The method of claim 9 , further comprising:

comparing the current through the single current sensor to a reference current to detect the occurrence of an overcurrent condition; and

controlling a position of a first switching device of the second inverter leg and a second switching device of the second inverter leg during the overcurrent condition.