Auto tuning of digital deadbeat current controller for grid tied inverters using wide bandwidth impedance identification

By injecting a wide-bandwidth small-amplitude test sequence into the inverter's PWM control signal and utilizing digital network analyzer techniques, an accurate estimation of the output impedance can be obtained without external equipment. This knowledge can then be leveraged to tune the inverter's digital deadbeat controller for optimal performance, i.e. reaching the desired reference in n switching cycles, where n is the order of the system. A pseudo-random binary sequence (PRBS) based injection sequence is chosen for its wideband spectral content.