Patent ID: 8773873

Claim:
A power conversion system for providing power to an electrical grid comprising: a power converter coupled to a power source and the electrical grid; at least one grid measurement device coupled to the power source and configured to measure a grid current and to generate a grid current feedback signal corresponding to the measured grid current; and a converter controller coupled to said power converter and said at least one grid measurement device and comprising: a control loop configured to generate a real voltage reference command and to receive a grid voltage feedback signal and demodulate the grid voltage feedback signal into a real voltage feedback component and a reactive voltage feedback component; and, a harmonic current reduction control loop coupled to said control loop and configured to generate a real harmonic cancellation voltage command and a reactive harmonic cancellation voltage command, said converter controller configured to combine the real voltage reference command and the real harmonic cancellation voltage command to generate an adjusted real voltage reference command; and said harmonic current reduction control loop configured to: receive the grid current feedback signal and a harmonic selection signal corresponding to a selected harmonic; extract a harmonic current component from the grid current feedback signal; demodulate the grid current feedback signal to generate a real grid current feedback signal and a reactive grid current feedback signal at a frequency associated with the selected harmonic; change a sign of a magnitude of the real grid current feedback signal to generate a real grid current cancellation signal; change a sign of a magnitude of the reactive grid current feedback signal to generate a reactive grid current cancellation signal; generate, using at least one current regulator, a real voltage cancellation reference command from the real grid current cancellation signal and a reactive voltage cancellation reference command from the reactive grid current cancellation signal; and generate, using a rotator and a demodulator, at least one harmonic cancellation voltage command based at least partially on the harmonic current component of the grid current feedback signal to control operation of said power converter to actively cancel harmonic current received at said power converter from the electrical grid.