Wide-bandwidth Identification of small-signal dq impedances of ac power systems via single-phase series voltage injection

The injection of single-phase wide-bandwidth signals into three-phase ac power systems significantly reduces measurement time using the hardware with minimized number of components. Interleaved transformer-less H-bridge converter is optimized to operate as a series voltage injector, increasing the low frequency injection range by avoiding transformer saturation problems. The decoupling control is implemented, providing the effective way to balance dc capacitor voltages and regulate the series injection voltage. The modular and scalable single-phase impedance measurement unit (IMU) is designed and constructed to inject chirp, multi-tone and sinusoidal signals in series with the three-phase ac power systems. The measurement system is designed to inject all three types of signals in the full frequency range, offering a trade-off between measurement time, identification process precision, and number of identification points. The effectiveness of the proposed identification approach is verified with the online estimation of source and load impedances of actively controlled programmable voltage source and a three-phase resistive load.